zircon geochemistry and geochronology of the seven devils …

ZIRCON GEOCHEMISTRY AND GEOCHRONOLOGY OF THE SEVEN DEVILS

MOUNTAINS, WESTERN IDAHO: TESTING PROPOSED TIES TO THE WRANGELLIA

TERRANE

A THESIS

SUBMITTED TO THE GRADUATE SCHOOL

IN PARTIAL FULFILLMENT OF THE REQUIREMENTS

FOR THE DEGREE

MASTER OF SCIENCE

BY

HEATHER CASARES

DR. KIRSTEN NICHOLSON- ADVISOR

DEPARTMENT OF GEOLOGICAL SCIENCES

BALL STATE UNIVERSITY

MUNCIE INDIANA

MAY 2019

i

Table of Contents

Chapter 1 Overview……………………………………………………………………………….1

Introduction………………………………………………………………………………..1

Previous Work…………………………………………………………………………….3

Objectives and Significance……………………………………………………………….4

Chapter 2 Background…………………………………………………………………………….6

Tectonics of Western North America……………………………………………………..6

Geologic Setting………………………………………………………………………..….9

The Blue Mountains Province…………………………………………………………….9

Wallowa terrane Seven Devils Group…………………………………………………..10

Baker terrane………………………………………………………………………….…13

Izee terrane………………………………………………………………………….…..13

Olds Ferry terrane……………………………………………………………………….13

Wrangellia…………………………………………………………………………….….14

Chapter 3 Analytical Methods…………………………………………………………..……….17

Sample Collection………………………………………….…………………………….17

Thin Section Preparation…………………………………………………………………19

Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS)

Analysis…………………………………………………………………………………..19

X-ray Fluorescence spectrometry (XRF) Analysis…………………………………..…..21

Chapter 4 Manuscript………………………………………………………………………….....24

Acknowledgements………………………………………………………………………………49

References………………………………………………………………………………………..50

Appendix……………………………………………………………………………………...….59

ii

List of Tables

Table A-1: U-Pb dating and of zircons from this study using LA-ICPMS…………………..…68

Table A-2: In Situ Lu-Hf isotopic data of zircons from this study…………………………..…..72

Table A-3: Average εHf(t) and errors for the Seven Devils samples……………...…………….73

Table A-4: Loss on Ignition (LOI)…………………………………………………………….....73

Table A-5: Whole Rock Geochemistry for the Seven Devils terrane determined by XRF……..74

iii

List of Figures

Figure 1-1: Location of the Seven Devils Mountains in Western Idaho………………………….1

Figure 2-1: Arc-arc collision model of the Blue Mountains Province……………………………8

Figure 2-2: The Blue Mountains Province and locations of terranes……………………………10

Figure 2-3: Close up view of the Wallowa terrane and rocks…………………………………..11

Figure 2-4: The location of the Wrangellia terrane……………………………………………..16

Figure 3-1: Sample location map…………………………………………………………...……18

Figure A-1: Sample SD001………………………………………………………………………60







Figure A-8: Sample SD008………………………………………………………...…………….67


Figure A-10: Average U-Pb ages for sample SD004…………………………………………….70



Figure A-13: Average U-Pb ages for sample SD008………………………………………….…71


Figure A-15: Volcanic Rock Diagram Using Immobile Trace Elements………………………..76

Figure A-16: Discriminate within-plate granites, volcanic arc granites & ocean ridge granites

using Nb vs. Y…………………………………………………………………………...………76

iv


using Rb vs. Nb+Y……………………………………………………………………………….77

1

Chapter One

1.1 Introduction

The western part of North America preserves a rich tectonic history. The western margin

of the North American Craton has many terrains and microcontinents that have accreted to it.

The boundary between terranes is known as the suture zone. These terranes and microcontinents

began forming during and after the breakup of Pangaea in the early Triassic (Murphy et al.,

2009). The forces created by such massive movement allowed for changes in the plate

boundaries which caused the Farallon plate to begin subducting off of North America (Sigloch

and Mihalynuk, 2013). The process of subduction ultimately created much of the volcanic arc

terranes and microcontinents that now form the North American Cordillera.

Figure (1-1) Location map of the Seven Devils Mountains field study area from (Farag,

2018).

2

The Seven Devils Mountains (Figure 1-1) are located along a 70 km stretch on the

eastern side of the Snake River in Western Idaho within an area known as Hells Canyon

Wilderness by the town of Riggings, Idaho (Sarewitz, 1983). The Seven Devils Mountains

consist of mostly intermediate to mafic igneous rocks with rare felsic rocks that have all been

variably metamorphosed. These rocks are considered to be the easternmost exposure of Permian

to Triassic volcanic rocks in the North American Cordillera (Vallier, 1977).

Modern analytical tools and scientific understanding of trace element chemistry has

improved significantly since the last study of the Seven Devils Mountains, conducted in the

1970s to the 1980s (Jones et al., 1977; Sarewitz, 1982). Conducting modern whole rock

geochemical analysis including major and trace element geochemistry, and zircon U-Pb

geochronology, will bring new insight on the formation of the Seven Devils, how volcanic arcs

evolve over time, and importantly, how western North America has evolved. The North

American Cordillera provides an excellent location to study terrane translation in an accretionary

orogeny. Previous studies and speculations have provided the Baja B.C. (Baja-British Columbia)

hypothesis of terrane transport (Champion et al., 1984; Umhoefer, 1987; Wyld and Wright,

2001; Wyld et al., 2006). Northward terrane transport in the Cordillera, such as the Wrangellia

terrane, is supported by fault displacements and paleomagnetic data suggesting displacements

from 1100 to 3000 km in Washington and the British Columbia (Champion et al., 1984; Wynne

et al., 1995; Wyld et al., 2006).

Trace element geochemistry, improved U-Pb geochronology, and Hf isotope analysis will

allow a better understanding of the tectonic history of the terrane and test models for northward

displacement of the arc, by allowing for robust comparisons with data from the Wrangellia

terrane and the surrounding Blue Mountains terranes. If the Seven Devils terrane is indeed part

3

of the Wrangellia terrane, then collected data will provide additional evidence for significant

long-range transport along the Cordilleran margin. If not, then the Seven Devils terrane may

represent an independent tectonic element of the Cordillera that may not require orogenic

displacement.

1.2 Previous Work

The main terranes (Wallowa, Baker, Izee, and Olds Ferry) of the Blue Mountains

Province formed as island arc systems along the continental margin of western Laurentia. The

Wallowa terrane has been known by many names such as the “volcanic arc terrane”, “Wallowa

Mountains–Seven Devils Mountains volcanic arc terrane” (Brooks and Vallier, 1978), and the

“Seven Devils terrane” (Vallier, 1977). The Wallowa terrane is the most outboard from the

continental margin and is an island arc terrane that formed in an intra- oceanic setting in the Blue

Mountains Province (LaMaskin et al., 2008; 2011). The Seven Devils terrane, which has been

interpreted to be part of the Wallowa terrane, and even the Wrangellia terrane, is a volcanic

complex in what is now western Idaho. Vallier (1977) described the Seven Devils and identified

four separate formations: The Permian Windy Ridge formation, Permian Hunsaker Creek

formation, Triassic Wild Sheep Creek formation, and the Triassic Doyle Creek formation. The

majority of the volcanic rocks in these formations were called spilite, keratophyre, and quartz

keratophyre. They are now reclassified as metabasalt, meta-andesite, metadacite, and

metarhyolite based on their greenschist metamorphic facies (Vallier et al. 2016). Previous work

comparing the Seven Devils to Wrangellia includes paleomagnetic studies, comparative studies

using fossils, and geochemistry.

Several authors including Hillhouse et al. (1982) and Harbert et al. (1995) worked to

provide evidence for the migration of the Wallowa and Wrangellia terranes using

4

paleomagnetism. The core samples collected for these studies include volcanoclastic

sedimentary, sedimentary, and volcanic flow rocks. Paleomagnetic data provide inclination and

declination information that yields a paleolatitude, as well as paleopole locations comparable to

other data sets. The two studies from Hillhouse in 1982 and again in 1984 on the Wallowa and

Wrangellia terranes respectively, provide a paleolatitude ranging from 10 to 18 degrees from the

Late Triassic in either the northern or southern hemisphere. The studies also show that there had

to have been some kind of rotation in the Seven Devils terrane in order to bring it to where it is

present day (Hillhouse, 1984).

Comparative fossil studies and the use of fossils were the main source for age dating the

surrounding rocks. The Seven Devils terrane contains fossils in the Wild Sheep Creek formation.

These fossils are concentrations of the bivalves Daonella degeeri and D. frami (Jones, 1977).

These fossils resemble others in beds beneath the Nikolai Greenstone of the Wrangellia terrane

in southern Alaska. The only other congeneric bivalves that resemble these two species are seen

in only two other localities in the Arctic and the western Pacific (Jones, 1977).

Very few geochronologic and geochemical analysis have been conducted on the

Wrangellia and Wallowa terranes. The majority of studies have used fossils to obtain an

estimated age for the Seven Devils terrane. U/Pb age dating is rare, with a few studies on detrital

minerals in sedimentary rocks. Only one geochemical study by Kurz (2016) was done on

intrusive rocks within the Wallowa region, but not specifically on the Seven Devils terrane.

Trace elements that are recorded include large-ion lithophile elements, high-field-strength

elements, and rare earth elements (LaMaskin et al., 2008). The collected data revealed that all of

the Blue Mountains Province are consistent with subduction-zone, arc origin based on the trace

element patterns and the rare earth element patterns vary from terrane to terrane. The rare earth

5

element patterns in the Wallowa terrane are indicative of first cycle volcanism in a forearc basin

with juvenile compositions (LaMaskin et al., 2008). These were necessary for the interpretation

and reconstruction of the geologic history of North America.

1.3 Objectives and Significance

The main objective of this study is to use a combination of whole rock geochemistry and

zircon U-Pb geochronology to constrain the ages of the four formations within the Seven Devils

Group, and to determine the tectonic setting and relationship to other exotic terranes along

western North America. These relationships can provide insight and help test how the Seven

Devils terrane fits into the proposed Baja BC hypothesis of northward terrane transport in the

Cordillera, using its proposed links to the Wrangellia terrane. Whole-rock geochemical analyses

from the 1970s and 1980s led authors to propose that the Seven Devils terrane was part of the

Wrangellia terrane, a volcanic arc terrane located further north in the Cordillera. Despite their

physical similarities, the distance between the terranes and significant geochemical differences

make correlation uncertain. Geochemistry and geochronology generated by this study will be

used to test models for northward displacement of the arc by allowing for robust comparisons

with extant data from Wrangellia. If the Seven Devils is indeed part of Wrangellia, then collected

data will provide additional evidence for significant long range transport along the Cordilleran

margin. If not, then the Seven Devils may represent an independent tectonic element of the

Cordillera that may not require long-distance orogenic displacement.

6

Chapter 2 Background

2.1 Tectonics of Western North America

Collisional plate boundaries along western North America have been active from the Late

Permian to present day. The main contributor to the deformation of western North America is

the closure of ocean basins and the subduction of the Farallon plate beneath Laurentia. This

active margin is preserved as the Cordillera; a group of accreted terranes and microcontinents

that formed on oceanic crust.

The Cordilleran margin, and more specifically the northern region of this margin,

recorded very complicated tectonics that included the accretion and transport of exotic terranes.

Remnants of subduction zones and strike slip faulting are observed in many regions. The study

of displacement along faults and the reconstruction of paleo-landforms help provide evidence for

an alternative model to the Baja B.C. hypothesis. The two original opposing models for the

terrane transport include: the accreted terranes originated just west of their current position

without any northward movement, and the second idea is the Baja B.C. hypothesis showing that

the terranes originated from just west of current day Mexico (Champion et al., 1984; Wynne et

al., 1995; Wyld et al., 2006). Movement began with Triassic to Late Jurassic terrane dispersal

and rotation. The extent of this movement is poorly constrained. Strike slip displacement in the

Cretaceous can be reconstructed using geochemical data, mapping the fault system, and

modeling. Various terranes have been displaced between 450 and 900 km to the north of their

original positions based on paleomagnetic data (Wyld et al., 2006). Far more detailed tectonic

models have been made for the Wallowa-Seven Devils terrane. The boundary between the

Wallowa-Seven Devils terrane and continental North America is marked by the western Idaho

shear zone. This is a zone dividing rocks with initial 87Sr/86Sr ratios < 0.704 in accreted terranes

7

to the west, and > 0.706 in the continental lithologies to the east (Strayer, 1989). The western

Idaho shear zone is thought to have mainly strike-slip movement defined by faulting,

geochemistry, and a sharp contrast in 87Sr/86Sr ratios on both sides of the shear zone. This is not

the only boundary between exotic terranes and continental North America. There are other shear

zones, including the Coast shear zone which separates the Wrangellia terrane and other northern

exotic terranes from North America (McClelland et al., 2000).

Tectonic models have been made to speculate what the Wallowa terrane might have

looked like at different points in geologic time (Figure 2-1). It is still unknown where the exact

location of the Wallowa-Seven Devils terrane originated, but there are some speculations from

paleomagnetic and geochemical studies (LaMaskin et al., 2011). These speculations, backed by

geochemical studies, suggest that the terrane originated somewhere on the oceanic plate as an

island arc (LaMaskin et al. 2008). There were two main subduction zones, and a possible strike-

slip fault that brought the Wallowa terrane to the continental margin. Both continental North

America and the Wallowa terrane are on separate plates divided by a small subducting oceanic

plate during the Mid-Triassic. Late Triassic plate motions brought the Wallowa terrane closer to

the continent as subduction formed an accretionary margin with the sedimentary Baker terrane.

The terrane appears to rotate in the Middle to early Late Jurassic, based on models with a large

fold and thrust belt on the eastern side of the terrane (LaMaskin et al., 2011).

8

Figure (2-1) The arc- arc collisional model for the Blue Mountains Provence (from fig. 12

Kurz et al., 2016). It combines paleomagnetic data and age data to determine the location of

the terrane at specific times. Geochemistry and general stratigraphy provides a rock based

record for the model. WSD- Wallowa Seven Devils; OF- Olds Ferry.

9

2.2 Geological Setting

The western part of North America is a mélange of accreted terranes. The more

geologically complex terranes that formed between the Permian and the mid-Cretaceous include

the Wrangellia terrane, and four terranes that reside within the Blue Mountains Province. These

four terranes are called Baker, Izee, Olds Ferry, and Wallowa. The Wrangellia terrane stretches

from southern Alaska down to northern Washington with the possibility of stretching further into

western Idaho. The Blue Mountains Province is located mostly in Oregon with some of the

terranes sitting on both sides of the Snake River.

2.3 The Blue Mountains Province

The Blue Mountains Province is the name of a mélange of pre-Tertiary igneous and

sedimentary rocks that are located in eastern Oregon, southeast Washington, and western Idaho

(Figure 2-2). The province is divided into multiple terranes defined by their separate geological

histories. Previous studies by Howard Brooks (1979) and Tracy Vallier (1977) divided these

terranes based on major faults and unconformities. The major faults and unconformities trend to

the east and northeast converging in the north towards the western Idaho shear zone (Tumpane,

2010). The terranes are characterized by their petrological and geochemical differences from the

North American Craton. It has been interpreted that during the late Jurassic the island arc

terranes of the Blue Mountains combined before their accretion to the continental margin in the

late Jurassic to early Cretaceous (Sarewitz, 1982). Blue Mountains Province contains two distinct

rock types: those that come from island arcs which include the Baker, Olds Ferry, and Wallowa

terranes, and those that are post-accretion to North America like the Izee terrane (Brooks, 1979).

Studies have strengthened the interpretation that the Baker, Izee, and Olds Ferry terranes formed

10

in close proximity to the continental margin, while the Wallowa formed as an intra-oceanic

island arc further out (LaMaskin et al., 2008; 2011).

2.3.1 Wallowa terrane Seven Devils Group

The Wallowa terrane (figure 2-3) is located in northeastern Oregon and western Idaho in

the North American Cordillera. The Wallowa terrane is often called “Wallowa Mountains–Seven

Devils Mountains volcanic arc terrane” or the “Seven Devils terrane” (Vallier, 1977). This

region is complex and its tectonic origins are continuously debated. The Wallowa terrane ranges

in age from Mid-Permian to Early Cretaceous, and contains a range of metamorphic, volcanic,

and sedimentary assemblages (Kurz et al., 2016). These rocks are variably metamorphosed to

mostly upper greenschist facies (Vallier et al., 2016). The lowest unit is called the Seven Devils

Group followed by late Triassic limestone and dolomite. On top of this are fine-grained

calcareous marine clastic rocks. There is a single potential unconformity in the Wallowa terrane,

along with many fossils within the sedimentary units. The potential unconformity is a

disconformity between the Seven Devils group and the Late Triassic limestone and dolomite

(Vallier, 1977).

Figure (2.2) The Blue

Mountains Province showing

the Wallowa, Baker, Izee,

and Olds Ferry Terranes. IB,

Idaho Batholith; SDM,

Seven Devils Mountains;

WISZ, Western Idaho Shear

Zone (from fig. 1 LaMaskin

et al., 2008).

11

The Seven Devils Group is an assemblage of Permian to Triassic volcanic and

sedimentary rocks within the Seven Devils Mountains. These mountains are situated on the

Idaho side of the Snake River. There are four formations including: Permian Windy Ridge

Formation, Permian Hunsaker Creek Formation; Triassic Wild Sheep Creek Formation; and

Triassic Doyle Creek Formation.

Figure (2-3) Close up view of the Wallowa terrane and associated rock types

(from fig. 2 Vallier et al., 2016).

12

The Permian Windy Ridge Formation is the oldest unit in the group. This formation is

dominated by pyroclastic and epiclastic rocks with epiclastic rocks being rare. The rocks tend to

be of pale green color. Rhyolitic pyroclastic breccia and tuff are the dominant types of rocks in

this formation. The major mineral components of these rocks are rhyolite rock fragments, quartz

(both primary crystals and secondary chalcedony), plagioclase feldspar (albite), opaque minerals

(including pyrite), chlorite, epidote, and sphene (Vallier, 2016). The age of this formation has

been inferred to be 268–248 Ma, but fossils and radioisotopic ages have not yet been obtained.

The Permian Hunsaker Creek formation overlays the Windy Ridge formation by a fault

contact. Rhyolitic and andesitic flows and volcaniclastic rocks dominate this formation. Basalt

and basaltic andesite are rare in this formation, but can be abundant in certain locations. This

formation also contains rhyolitic and basaltic diabase and gabbro that are hypabyssal

intrusive rocks (Vallier, 2016). Rhyolites within this formation are generally rich in silica and

sodium and have little to no potassium and calcium (Vallier, 1995). This is different compared to

the traditional rhyolite that typically has more potassium and calcium.

The Triassic Wild Sheep Creek Formation is above the Hunsaker Creek Formation. This

formation commonly contains massive lava flows and intrusive hypabyssal rocks such as basalt

and rhyolite. Pyroclastic rocks are a minor contributor to this formation and are abundant is only

a few areas. Typical colors of the rocks are grey to green with even rarer colors of red to brown.

Epiclastic rocks in the Wild Sheep Creek Formation include conglomerate, breccia, sandstone,

and mudstone. This formation is metamorphosed to greenschist and zeolite facies (Vallier et al.,

2016).

The youngest formation in the Seven Devils is the Doyle Creek Formation. It is only

slightly younger than the Wild Sheep Creek Formation with an overlap in ages. It consists of

13

lava flows, most of which are basalt, basaltic andesite, and dacite, and volcaniclastic rocks

(Vallier et al., 2016). The color of the rocks in this formation are mostly red to maroon with

some pale green in color. The metamorphic grade is upper greenschist facies.

2.3.2 Baker terrane

The Baker terrane is one of the four terranes in the Blue Mountains Province. The Baker

terrane is the most complex out of all the Blue Mountains terranes. It is made up of accretionary-

complex and intra-arc to forearc-basin deposits (Gray and Oldow, 2005). The terrane is divided

into two different subterranes: the Bourne and Greenhorn subterranes (Ferns and Brooks, 1995).

The Bourne subterrane is composed of a mélange of chert-argillite and the rocks are mostly

radiolarian chert, cherty argillite, argillite, basalt, and limestone olistoliths (Vallier, 2016). The

Greenhorn subterrane is a mixture of igneous and sedimentary rocks that are in a serpentine

mixture (Vallier, 2016).

2.3.3 Izee terrane

The Izee terrane is made up of accretionary-complex and intra-arc to forearc-basin

deposits. These deposits are made up of clastic sedimentary rocks (LaMaskin et al., 2011). This

makes it similar to and causes it to be confused with being a part of the Baker terrane or the Olds

Ferry terrane. It has been interpreted by many authors that the Izee terrane sits depositionally on

top of the Baker terrane (LaMaskin et al., 2011) and is separated from the Olds Ferry terrane by a

thrust fault that was originally a depositional contact (Tumpane, 2010).

2.3.4 Olds Ferry terrane

The Olds Ferry terrane is younger than the Wallowa terrane. The late Middle Triassic to

Late Triassic terrane consists of plutons. Speculations suggest that the arc formed partially on the

Wallowa arc making it an extension of it or that it was its own tectonic element fringing the

14

North American Craton (Vallier, 1995). The Olds Ferry terrane is the only other arc that formed

in an oceanic setting (Gray and Oldow, 2005). The Olds Ferry terrane contains the Huntington

Formation; an assemblage of carbonate and clastic sedimentary rocks along with metavolcanic

rocks and some plutonic rocks (Brooks and Vallier, 1978). The formation of the Olds Ferry

volcanic submarine arc is interpreted to be late Triassic based upon fossils in the fossiliferous

limestone (Vallier, 1995). All of the Olds Ferry rocks have been regionally metamorphosed to

zeolite and greenschist facies.

2.4 Wrangellia terrane

The Wrangellia terrane (Figure 2-4) is split between four areas: the Wrangell Mountains

in Alaska, Chichagof Island, Queen Charlotte Islands, and Vancouver Island. The Wallowa

terrane in northeastern Oregon is often included as this terrane’s southeastern most extension

(Jones et al., 1977). Nearly 2000 km separate the main four sections of the Wrangellia terrane

(Jones et al., 1977). These four sections are combined into one terrane because of similar

lithology, fossil assemblages, structure, and unconformities.

The stratigraphy of Wrangellia consists of sedimentary, volcanic, and low-grade

metamorphic rocks from the Lower Permian to early Jurassic. The oldest units contain Lower

Permian argillite and limestone (Jones et al., 1977). The unit above this is a 100 m Mid-Triassic

sequence of gray- black thinly bedded chert, siltstone, and fissile shale (Jones et al., 1977). In the

Middle to Late Triassic period there was volcanic activity constrained by K-Ar and U-Pb

geochemical age dating on Jurassic Plutons and fossils from sedimentary rocks (Samson et al.,

1990). Some low-grade metamorphism to greenstone is visible. This large 3,500 m Mid to Late

Triassic unit makes up the majority of the stratigraphic sequence. The unit consists of

greenstone, basaltic flows, pillow lavas, sills, and tuff (Jones et al., 1977). Most of the greenstone

15

is concealed, but the basalts and pillow lavas are exposed throughout all the areas. Above this are

mostly Triassic sedimentary rocks, consisting of limestone, calcareous shale, and chert (Jones et

al., 1977). One of the four regions located on Chichagof Island has marble, suggesting an event

of metamorphism within that region. There is an intrusion of granodiorite dated to the Jurassic

from 185 to 190 Ma (Samson et al., 1990). These units follow a similar pattern to the Seven

Devils terrane.

Two unconformities and different invertebrate fossils are observed within the Wrangellia

terrane. A disconformity lies between the lowest unit which is Lower Permian and the above

Mid-Triassic unit. There is a nonconformity between the thick greenstone and volcanic sequence

with the sedimentary units above it (Jones et al., 1977). There are a few fossils of bivalves in the

lowest unit. The upper sedimentary units contain stromatolites, gastropods, bivalves,

brachiopods, corals, spongiomorphs, cephalopods, and echinoderms (Jones et al., 1977).

16

Figure 2-4: The Location of the Wrangellia terrane and proposed southern portion as the

Seven Devils Mountains (from fig. 1 Jones et al., 1977).

17

Chapter 3 Analytical Methods

3.1 Sample Collection

One set of nine samples was collected during a field excursion in July of 2018. The

excursion took roughly nine days traveling from Muncie, Indiana, to the Seven Devils Mountains

near Riggins, Idaho. Sample locations were remote and far from the main Seven Devils

Campground and it was necessary to backpack and temporarily camp along the trail (Figure 3-1).

Samples were collected all along the loop trail which includes trail 124 and 101. The spread of

samples was located on both the east and west sides of the Seven Devils Mountains. Hand

samples mostly consisted of intermediate igneous rocks with one being more mafic. See figures

A-1 to A-9 for sample descriptions.

18

Figure (3-1) Sample location map. Shows locations for SD001-009.

19

3.2 Thin Section Preparation

The thin sections were prepared using standard methods at Ball State University. The

rock samples were cut into 1”x2’ billets using a rock saw. Then, the side of each sample was

polished and glued to a slide and cleaned to remove fractured areas. Polishing was done by using

the metal wheel with 120, 220, 400, and 600 alumina grits. Finally, to ensure a good surface it is

polished again on glass with 600 and 1000 alumina grits for 2 to 3 minutes. The billets on the

glass slide were then cut down to an appropriate size using the saw arm of a Hillquist 1010 thin

section machine. Then the billets were ground down using the thin section machine to about 10-

20 μm greater than final desired thickness (Lange 2014). The slides were then polished on a glass

plate using 600 and 1000 alumina grits until plagioclase was identifiable in a microscope. For

sample descriptions see appendix figures A-1 to A-9.

3.3 Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) Analysis

U-Pb geochronology and Lu-Hf isotope geochemistry on the collected samples was

conducted at the LaserChron lab located at the University of Arizona in Tucson.

The zircons are extracted from the sample and prepared for analysis using standard

methods (Kröner et al., 2000) including the following steps: Each igneous rock sample is broken

to a small enough size to fit in the jaw crusher using a sledge hammer. Then, they are put

through a two-step process to crush the sample to a fine < 500 µm size. The first step is to run

the sample through a BICO Chipmunk jaw crusher in order to reduce the rock into gravel sized

particles. The next step is the BICO disk mill which uses two spinning steel plates to pulverize

the material into a sand-sized fraction. This sediment is run across a Gemini GT-60 shaker table

that uses water, along with a constant shaking motion to separate the denser minerals from

lighter ones such as quartz and feldspar. The denser material is caught in three buckets, one in

20

the center and two on the sides. These fractions are rinsed in acetone and dried, with the center

bucket containing an enriched heavy mineral fraction used in the final processes. This dense

fraction is then run across a Franz Isodynamic magnetic separator, with a 20º forward and a 10º

side tilt, and a current range from 0.2 to 0.7 Å. This process removes high magnetic

susceptibility material from the sample before further processing. Methylene iodide (MeI) is a

heavy liquid used to separate the densest minerals from the lighter ones. Dense minerals,

including zircon, will sink to the bottom of the container with the liquid, where they can be

extracted by opening a stopcock in the base of the separatory funnel for filtering and cleaning.

They are rinsed in acetone and dried to make sure the MeI is no longer on the sample. This

material is then run through the magnetic separator with a current of 1.0 to 1.8 A, further

purifying the sample. The resulting separate is then picked for zircon grains that show the least

defects.

The samples were sent to University of Arizona’s LaserChron lab to be mounted for

analysis. The high-quality grains were mounted with standards Sri Lanka, FC-1, and R33. The

mounts were sanded down to a depth of ~20 microns, polished, imaged using high resolution

cathodoluminescence (CL) and backscattered electron (BSE) images. These images are

important because they help distinguish zircons from apatite and allow for a closer up image for

spot picking to avoid any inclusions or cracks in the zircon.

U-Pb analysis was conducted by LA-ICPMS at the University of Arizona’s LaserChron

Center using standard methods (Gehrels et al., 2006, 2008; Gehrels and Pecha, 2014). The

analyses involve using a Photon Machines Analyte G2 Excimer laser with a spot diameter of 40

microns to get rid of any added Pb and again at 20 microns to ablate the zircon. The material is

then carried in helium to the plasma source of an Element2 HR ICP-MS, which sequences

21

rapidly through U, Th, and Pb isotopes. The intensities of these signals are measured with a

SEM. The ratios of U and Pb are then calculated. The calculated ages are shown on U-Pb

concordia diagrams and weighted mean diagrams using the routines in Isoplot (Ludwig, 2008).

Hf isotope analyses was conducted with a Photon Machines Analyte G2 excimer laser in

situ of U-Pb spots according to standard methods (Cecil et al., 2011; Mueller et al., 2008). The

instrument settings were established for Hf analysis by analysis of 10 ppb solutions of JMC475

and a Spex Hf solution, and then by analysis of 10 ppb solutions containing Spex Hf, Yb, and

Lu. Several different standards: Sri Lanka, FC-1, and R33 are analyzed for precision and

accuracy before the unknowns. The CL images are used to ensure that the ablation pits do not

overlap multiple domains or inclusions. The samples are analyzed with a laser beam diameter of

40 microns. The Lu and Hf isotopes are calculated and an epsilon plot is created to show where

the samples sit compared to the depleted mantle and the Chondritic Uniform Reservoir (CHUR)

line. The 176Hf/177Hf at time of crystallization is calculated after the analysis using measurements

of present-day 176Hf/177Hf and 176Lu/177Hf, using the decay constant of 176Lu (λ = 1.867e-11)

from Scherer et al. (2001) and Söderlund et al. (2004).

3.4 X-ray Fluorescence spectrometry (XRF) Analysis

XRF analysis is conducted in house at Ball State University. Pellets are made for the

XRF by a simple process. The rock is cut down by a rock saw into small cubes and polished

using 200 grit followed by 600 grit to remove any residue and contamination from the saw. The

polished cubes are put through the tungsten carbide ring mill C+CR machine for 35-60 seconds

and crushed into a fine powder. Around 9 to 10 grams of each sample was weighed and put into

a weighed ceramic crucible. This is then poured into a plastic ceramic mixing cup. Polyvinyl

alcohol (PVA) was made and used to make the mixture more saturated and homogenous. The

22

PVA solution had been mixed using 5 g of dried 85-90% hydrolyzed grains and 95 g (95 mL)

18Ω deionized water. The mixture was heated and stirred until the PVA grains had dissolved.

Nineteen drops of PVA were added into the 8 grams of each sample’s powder, and then the

mixture was mixed until it became homogeneous. A pellet press apparatus was used to make the

pellets. Powder was poured inside the piston press and pressed at 2-10 tons/in2 for 5-10 sec for

three minutes. Pellets were carefully extracted and set to dry in a Fischer Scientific Isotemp

Oven at 50˚C.

Samples were analyzed using methods from Eric Lange 2019. The Samples were

analyzed using a Thermo Noran (now Thermo Fisher) QuanX energy dispersive X-ray

fluorescence (ED-XRF) analyzer with WinTrace spectrum processing software. There are 4

different conditions used when analyzing samples in order to optimize the fluorescence yield for

the elements of interest. Excitation energies for each condition were 6, 12, 16, and 30 keV which

used no filter, an Aluminum, a thin Palladium, and a thick Palladium filter for each energy

respectively. Each sample was run for 300 seconds of live time, which approximates to about

2700 seconds of total analysis time for nine samples. Abundances were determined using counts

per second within a narrow keV range specific to each element. This was divided by the different

currents used. The elements were calibrated linearly using a series of 13 standards supplied by

the USGS: AGV-2, BCR-2, BHVO-2, BIR-1a, COQ-1, DNC-1a, DTS-2b, GSP-2, QLO-1, SBC-

1, SDC-1, SGR-1b, and W-2a.

The amount of volatiles is calculated by a loss on ignition (LOI) procedure appropriate

for intermediate, mafic, and ultramafic rocks with moderate to high amounts of clay alteration.

The powders made out of each rock were used in this process. Around 8 to 10 grams of each

sample was weighed and placed into a weighed ceramic crucible that weighed approximately 2.4

23

grams. The total weight for both the powder and crucibles were recorded before placing them

overnight in a Fischer Scientific Isotemp Oven at 65˚C. The following day, all samples were

taken out, and the weight was measured for each sample. After that, all samples were put back in

for 110 ˚C and measured once again the next day. The final measurement was taken on the

samples after they were put into the thermo Scientific Thermolyne F48015-60 muffler furnace at

1000 ˚C. The new weight percent lost was reported as LOI.

24

Chapter 4 Manuscript

Zircon U-Pb Geochronology and Hf Isotope Geochemistry of the Seven Devils Mountains,

Western Idaho: Testing proposed ties to Surrounding Terranes

Abstract

The North American Cordillera provides an excellent location to study terrane

translations in an accretionary orogeny. Some previous studies have proposed the Baja -British

Columbia hypothesis of northward terrane transport in the Cordillera. This has been supported by

fault displacements and paleomagnetic data showing displacements from 1100 to 3000 km in

Washington and British Columbia. The Seven Devils Mountains are located in the Wallowa-

Whitman National Forest in western Idaho. This geologically complex and variably

metamorphosed terrane preserves a Permo-Triassic volcanic arc accreted against the Cordilleran

margin. Whole-rock geochemical analyses from the 1970s and 1980s led authors to propose that

the Seven Devils terrane was part of the Wrangellia terrane, a volcanic arc terrane located further

north in the Cordillera. Despite their physical similarities, the distance between the terranes and

significant geochemical differences make correlation uncertain. Zircon U-Pb and Lu-Hf was

used to test proposed ties to Wrangellia terrane and the neighboring Blue Mountains Province

terranes. LA-ICPMS zircon U-Pb dating on 6 intermediate intrusive samples yield ages ranging

from 120.1 ± 1.0 Ma to 137± 2.0 Ma with the average age of 127 ± 7.8 Ma. All the samples have

similar Lu-Hf isotopic compositions, with a range in εHf(t) of 8.6 to 13.8 with the average εHf(t)

value of 10.8 ± 1.2. Isotopic data and ages show that the intrusive rocks were forming close to

the time of accretion. These new data, combined with previous age and isotope data from the

surrounding terranes suggest that the Seven Devils terrane is the most similar to the terranes in

the Blue Mountains Province and not a match to the Wrangellia terrane.

Introduction

25

The western part of North America preserves a rich tectonic history. The western margin

of the North American Craton has many terrains and microcontinents that have accreted to it

after forming during and after the breakup of Pangaea in the early Triassic (Murphy et al., 2009).

The forces created by such massive movement allowed for changes in the plate boundaries which

caused the Farallon plate to begin subducting off of North America (Sigloch and Mihalynuk,

2013). These forces ultimately created much of the volcanic arc terranes and microcontinents

that now form the North American Cordillera. While Late Paleozoic to Mesozoic volcanism and

accretion is agreed upon by many authors (Burchfiel et al., 1992; Dickinson, 2004; Gray, 2013)

there are some controversies revolving around the origin of a terrane in the Blue Mountains

Province (BMP) known as the Seven Devils terrane (Jones et al., 1977; Sarawitz, 1983;

Hillhouse and Gromme, 1984; Kalk, 2008).

The origin of the Seven Devils terrane has been questioned and disputed by many studies.

The Seven Devils terrane has been correlated with the greater the Wrangellia terrane (Hillhouse

and Gromme, 1984; Jones et al., 1977; Samson et al., 1990) and the Wallowa terrane (Gray and

Oldow, 2005; LaMaskin et al., 2015; Schwartz et al., 2011); however, it could also have been a

separate tectonic element. Correlation with the Wrangellia terrane provides its own set of

problems of terrane transport due to the distance between the terranes. Previous studies and

speculations have provided the Baja-British Columbia (Baja-B.C.) hypothesis of terrane

transport (Champion et al., 1984; Umhoefer, 1987; Wyld and Wright, 2001; Wyld et al., 2006).

Northward terrane transport in the Cordillera has already been supported by fault displacements

and paleomagnetic data showing displacements from 1100 to 3000 km in Washington and

British Columbia (Champion et al., 1984; Wynne et al., 1995; Wyld et al., 2006).

26

The Seven Devils terrane is a unique tectonic element along the western Idaho shear

zone. If it is indeed part of the Wrangellia terrane it can provide further evidence for long ranged

terrane transport along the shear zone. If not, the terrane may belong to surrounding terranes or

might be its own separate tectonic element. New data will help show how the isotope

geochemistry of the rocks reacts to being right on the edge of the sharp shear zone boundary of

Laurentia, provide a more robust dataset for the Seven Devils terrane, and contribute to the

tectonic history of North America.

In this contribution, we report zircon U–Pb ages and Lu-Hf isotopic compositions of the

intrusive rocks from the Seven Devils terrane. Based on the results, we discuss the origin of the

Seven Devils terrane and the timing of amalgamation with the North American Craton.

Geologic setting

Blue Mountains Province

The Blue Mountains Province is the name of a mélange of pre-Tertiary igneous and

sedimentary rocks that are located in eastern Oregon, southeast Washington, and western Idaho

Fig. 1 An overall view of

the Blue Mountains

Province and associated

terranes taken from fig. 1

(LaMaskin et al., 2008).

The IB, Idaho Batholith;

SDM, Seven Devils

Mountains; SRB, Salmon

River Basin; WISZ,

Western Idaho Shear

Zone are shown along

with the terrane

boundaries in dashed

lines.

27

(Fig. 1). The province is divided into multiple terranes defined by their separate geological

histories. Previous studies by Brooks (1979) and Vallier (1977) divided these terranes based on

major faults and unconformities. The major faults and unconformities trend to the east and

northeast converging in the north towards the western Idaho shear zone (Tumpane, 2010). The

terranes are characterized by their petrological and geochemical differences from the North

American Craton. The four distinct terranes in the Blue Mountains Province are called Baker,

Izee, Olds Ferry, and Wallowa terranes. It has been interpreted that during the late Jurassic the

island arc terranes of the Blue Mountains combined before their accretion to the continental

margin in the late Jurassic to early Cretaceous (Sarewitz, 1982). The Blue Mountains Province

contains two distinct rock types: those that come from island arcs which include the Baker, Olds

Ferry, and Wallowa terranes, and those that are post-accretion to North America like the Izee

terrane (Brooks, 1979). Studies have strengthened the interpretation that the Baker, Izee, and

28

Olds Ferry terranes formed in close proximity to the continental margin, while the Wallowa

formed as an intra-oceanic island arc further out (LaMaskin et al., 2008; 2011).

The Wallowa terrane (Fig. 2) is located in northeastern Oregon and western Idaho in the

North American Cordillera. The Wallowa terrane is often called “Wallowa Mountains–Seven

Devils Mountains volcanic arc terrane” or the “Seven Devils terrane” (Vallier, 1977). This

region is complex, and its tectonic origins are continuously debated. For example, it has been

often linked to the Wrangellia terrane (Jones et al., 1977). The Wallowa terrane ranges in age

from Mid-Permian to Early Cretaceous, and contains a range of metamorphic, volcanic, and

sedimentary assemblages (Kurz et al., 2016). These rocks are variably metamorphosed to mostly

upper greenschist facies (Vallier et al., 2016). The lowest unit is called the Seven Devils Group

Fig. 2 Wallowa terrane located in

the Blue Mountains Province

showing a close up view of the

rock types in the area from fig. 2

(Vallier et al., 2016). The Seven

Devils Mountains are located in

the middle of the map near the

arc continent boundary.

29

followed by late Triassic limestone and dolomite. On top of this are fine-grained calcareous

marine clastic rocks. There is a single potential unconformity in the Wallowa terrane, along with

many fossils within the sedimentary units. The potential unconformity is a disconformity

between the Seven Devils group and the Late Triassic limestone and dolomite (Vallier, 1977).

Wrangellia terrane

The Wrangellia terrane (Fig. 3) is split between four areas: the Wrangell Mountains in

Alaska, Chichagof Island, Queen Charlotte Islands, and Vancouver Island. The Wallowa terrane

in northeastern Oregon is often included as this terrane’s southeastern most extension (Jones et

al., 1977). Nearly 2000 km separate the main four sections of Wrangellia terrane (Jones et al.,

1977). These four sections are combined into one terrane because of similar lithology, fossil

assemblages, structure, and unconformities.

The stratigraphy of the Wrangellia terrane consists of sedimentary, volcanic, and low-

grade metamorphic rocks from the Lower Permian to early Jurassic. The oldest units contain

Lower Permian argillite and limestone (Jones et al. 1977). The unit above this is a 100 m Mid-

Fig. 3 Map of the Wrangellia Terrane updated from

fig. 1 (Hillhouse and Gromme, 1984). WM-

Wrangell Mountains, CI-Chichagof Island, QCI-

Queen Charlotte Islands, VI-Vancouver Island

30

Triassic sequence of gray- black thinly bedded chert, siltstone, and fissile shale (Jones et al.,

1977). In the Middle to Late Triassic period there was volcanic activity and some low-grade

metamorphism indicated by geochemical age dating. This large 3,500 m Mid to Late Triassic

unit makes up the majority of the stratigraphic sequence. The unit consists of greenstone, basaltic

flows, pillow lavas, sills, and tuff (Jones et al., 1977). Most of the greenstone is concealed, but

the basalts and pillow lavas are exposed throughout all the areas. Above this are mostly Triassic

sedimentary rocks, consisting of limestone, calcareous shale, and chert (Jones et al., 1977).

Two unconformities and different invertebrate fossils are observed within the Wrangellia

terrane. A disconformity lies between the lowest unit which is Lower Permian and the above

Mid-Triassic unit. There is a nonconformity between the thick greenstone and volcanic sequence

with the sedimentary units above it (Jones et al., 1977). Few bivalves are observed in the lowest

unit, while the upper sedimentary units contain stromatolites, gastropods, bivalves, brachiopods,

corals, spongiomorphs, cephalopods, and echinoderms (Jones et al., 1977).

Geology of the Seven Devils terrane

The Seven Devils terrane is an assemblage of Permian to Triassic volcanic and

sedimentary rocks within the Seven Devils Mountains. These mountains are situated on the

Idaho side of the Snake River. There are four formations within the Seven Devils terrane:

Permian Windy Ridge Formation, Permian Hunsaker Creek Formation; Triassic Wild Sheep

Creek Formation; and Triassic Doyle Creek Formation.

The Permian Windy Ridge Formation is the oldest unit in the group. This formation is

dominated by pyroclastic and epiclastic rocks with epiclastic rocks being rare. The rocks tend to

be pale green in color. Rhyolitic pyroclastic breccia and tuff are the dominant types of rocks in

this formation. The major mineral components of these rocks are rhyolite rock fragments, quartz

31

(both primary crystals and secondary chalcedony), plagioclase feldspar (albite), opaque minerals

(including pyrite), chlorite, epidote, and sphene (Vallier et al., 2016). The age of this formation

has been inferred to be 268–248 Ma, but fossils and isotopic ages have not yet been obtained.

The Permian Hunsaker Creek formation overlays the Windy Ridge formation by a fault

contact. Rhyolitic and andesitic flows and volcaniclastic rocks dominate this formation. Basalt

and basaltic andesite are rare in this formation but can be abundant in certain locations. This

formation also contains rhyolitic and basaltic diabase and gabbro that are hypabyssal

intrusive rocks (Vallier et al., 2016). Rhyolites within this formation are generally rich in silica

and sodium and have little to no potassium and calcium (Vallier, 1995). This is different

compared to the traditional rhyolite that typically has more potassium and calcium.

The Triassic Wild Sheep Creek Formation is above the Hunsaker Creek Formation. This

formation commonly contains massive lava flows and intrusive hypabyssal rocks such as basalt

and rhyolite. Pyroclastic rocks are a minor contributor to this formation and are abundant in only

a few areas. Typical colors of the rocks are grey to green with even rarer colors of red to brown.

Epiclastic rocks in the Wild Sheep Creek Formation include conglomerate, breccia, sandstone,

and mudstone. This formation is metamorphosed to greenschist and zeolite facies (Vallier et al.,

2016).

The youngest formation in the Seven Devils is the Doyle Creek Formation. It is only

slightly younger than the Wild Sheep Creek Formation with an overlap in ages. It consists of

32

lava flows, most of which are basalt, basaltic andesite, and dacite, and volcaniclastic rocks

(Vallier et al., 2016). The color of the rocks in this formation are mostly red to maroon with

some pale green. The metamorphic grade is upper greenschist facies.

The samples for this study were taken from the Wild Sheep Creek Formation in the

Seven Devils Mountains. These nine samples include porphyritic basalt, diorite, granodiorite,

and syenitic diorite based off XRF analysis in table A-5 and figure A-15 intrusive rock diagram

Fig. 4 Location of collected samples within the Seven Devils Mountains.

33

for immobile trace elements. The majority of these samples except for the basalt were taken from

intrusions within the formation that are seen throughout the Blue Mountains Province terranes.

These are all slightly metamorphosed to greenschist facies. Sample locations for this study are

shown in Fig. 4.

Analytical Methods

Zircon U-Pb dating and Hf analysis

Representative samples from the Seven Devils terrane were collected and selected for

zircon separation and U-Pb analyses. Out of nine samples collected five yielded zircons. Zircon

analysis for intrusive igneous rocks (SD004, SD006, SD007, SD008, SD009) were performed by

Laser Ablation ICPMS (LA-ICPMS) at the Arizona LaserChron Center, University of Arizona,

United States, according to standard methods (Gehrels et al., 2006, 2008; Gehrels and Pecha,

2014). The analyses involve ablation of zircon with a Photon Machines Analyte G2 Excimer

laser using a spot diameter of 20 microns for U-Pb. All U-Pb data were using Sri Lanka, FC-1,

and R33 as standards. The data was calculated by in-house Python decoding routine and an Excel

spreadsheet at the University of Arizona. Hf isotope measurements were made via ablation on

top of the preexisting U-Pb pits using a spot size of 40 microns. Cathodoluminescence images

were used to ensure that the spots did not overlap multiple age domains or inclusions.

Results

Zircon U–Pb geochronology

New U-Pb dates of zircons from intermediate intrusive rocks were obtained using LA-

ICP-MS at the University of Arizona LaserChron lab. Five samples were dated and reported as

207Pb corrected 206Pb/238U ages. The analytical results of samples from diorite to granodiorite are

34

presented in Table A-1 with Concordia diagrams in Fig. 5 and zircon CL images are shown in

Fig. 6.

Zircon grains from sample SD004 display little to no oscillatory zoning with size ranging

from 100 µm to 350 µm in length to 50 µm to 100 µm in width. The Th/U ratios of the analyzed

fifteen zircon grains range from 0.24 to 0.57. These numbers suggest a magmatic origin for the

zircons. This is the stratigraphically highest sample dated in this study. All fifteen of the grains

have overlapping errors and they give a weighted mean 206Pb/238U age of 137± 2.0 Ma.

Fig. 5 Concordia diagrams for each sample

with the age included.

Fig. 5 Concordia diagrams for each

sample with the Concordia age and the

mean age.

35

Zircons from SD006 display little to no oscillatory zoning with zircon size ranging from

100 µm to 300 µm in length to 50 µm to 150 µm in width. The Th/U ratios of the analyzed

fifteen zircons range from 0.27 to 0.66. The Th/U ratios suggest a magmatic origin. One zircon

was an outlier with an age of 114.7 ± 1.3 Ma and was not included in the overall age calculation.

This sample has a weighted mean 206Pb/238U age of 123.0 ± 1.7 Ma.

Zircons from sample SD007 display very clear oscillatory zoning on most of the grains

and the zircon size ranges from 100 µm to 300 µm in length and 50 µm to 150 µm in width. The

Th/U ratios of the fifteen analyzed zircons range from 0.19 to 0.51. The Th/U ratios are

suggestive of a magmatic origin for the zircons. Only 2 zircon ages were manually rejected for

being much older than the average. These two grains were 127.5 ± 1.8 Ma and 126.9 ± 1.5 Ma.

The weighted mean for the sample 206Pb/238U age is 120.1 ± 1.1 Ma.

Zircons from SD008 displays some clear oscillatory zoning and the zircon size ranges

from 50 µm to 300 µm in length and 50 µm to 150 µm in width. The Th/U ratios of the fifteen

analyzed zircons range from 0.13 to 0.22. The Th/U ratios are suggestive of a magmatic origin.

SD008 is one of the stratigraphically lowest samples. Only one zircon was rejected because it is

the oldest age and has the highest correction error. The weighted mean 206Pb/238U age is 120.0 ±

1.0 Ma.

Zircons from sample SD009 display little to no oscillatory zoning and the range in size is

from 50 µm to 450 µm in length and 50 µm to 100 µm in width. The Th/U ratios of the fifteen

analyzed zircons range from 0.21 to 0.40. The ratios are suggestive of a magmatic origin. Sample

SD009 is the easternmost and lowest stratigraphic sample. Only one zircon age was rejected for

being too young at 116.5 ± 1.1 Ma. The weighted mean 206Pb/238U age is 135.7 ± 1.9 Ma.

36

Fig. 6 Cathodoluminescence imaging of zircons that were age dated and had isotopic Lu-Hf analysis.

The zircon spots are marked with black circles.

37

In Situ Zircon Lu-Hf Isotopes

The Hf isotope results of the zircons from the five Seven Devils samples are listed in

Table A-2 and graphed on an epsilon plot in Fig. 7. The five samples; SD004, SD006, SD007,

SD008, and SD009 that all had ages ranging from 136.7 to 120Ma have εHf(t) values from 8.6 to

13.8. SD004 has an average εHf(t) value of 11.7. SD006 has an average εHf(t) value of 11. SD007

has an average εHf(t) value of 10.8. SD008 has an average εHf(t) value of 10.4. SD009 has an

average εHf(t) value of 10.1. These εHf(t) values are very tight showing errors of 0.5 to 0.9 with

no distinct differences in the samples. The TDM model age for the samples is 470 Ma to about

240 Ma. There appears to be no distinct pattern or differences between any of the samples.

Discussion

Zircon Age Relationships

Previous geochronologic investigations on the Seven Devils terrane are sparse and most

of the ages are derived from the Wallowa terrane. The ages of the basement rocks are Permian to

Triassic (Vallier and Brooks, 1986). The Seven Devils terrane is often thought to be part of either

the Wrangellia terrane, Wallowa terrane, or as a separate terrane that does not belong to either of

Fig. 7 εHf(t) values displayed

on an epsilon plot. DM-

Depleted Mantle, CHUR-

Chondritic Uniform

Reservoir. All the values plot

on the positive side of the

CHUR line.

38

them. The idea that the Seven Devils terrane could be part of one of these greater terranes comes

from the fact that they are stratigraphically similar with similar fossils.

The Seven Devils rocks in this study have an overall age range from 136.7 Ma to 120.0

Ma. This age range coincides with the ages of plutons throughout the Blue Mountains Province.

All of the terranes in the Blue Mountains province were intruded by post-kinematic Late Jurassic

to Early Cretaceous calc-alkaline plutons (Gray and Oldow, 2005). The ages from these plutons

provide an upper age constraint for the Late Jurassic tectonic amalgamation of terranes outboard

of the continental margin (Vallier and Brooks, 1986; Walker, 1986; Avé Lallemant, 1995; Snee

et al., 1995). The U-Pb age ranges from the plutons found throughout the Blue Mountains

province are collected from zircons dating 145 Ma to 120 Ma (Walker, 1989). These plutons

constrain the age of deformation because they crosscut deformed rocks. A quartz diorite pluton

outcrops on the western side of the Seven Devils mountains. It has been K/Ar-dated to early

Cretaceous 115 Ma from biotite and hornblende (Vallier, 1995).

Several deformational events have been documented in the Blue Mountains Province.

The oldest documented dynamothermal event occurred during the amalgamation of the terranes

between 144 and 142 Ma (Gray and Oldow, 2005). Another important event occurred between

129 and 100 Ma in the belt of rocks along the terrane boundary with the North American Craton

(Davidson, 1990). This event was recorded with Ar40/Ar39 dates of plutons and metamorphism in

the northern part of the Wallowa terrane.

The Seven Devils terrane is also linked to the Wrangellia terrane which spans from

Alaska to northern Washington with the possibility of including the Seven Devils terrane in

western Idaho. The Wrangellia terrane has different Rb-Sr and U-Pb ages of granodiorite plutons

from the different terrane segments. The ages of the granodiorite plutons from Vancouver Island,

39

the closest segment to the Seven Devils terrane, are between 185 and 190 Ma (Armstrong, 1988;

Sampson et al., 1990). The slightly younger Queen Charlotte Islands have plutons around 172

Ma age and the Burnaby Island suite ranges from 158 to 168 Ma (Anderson and Reichenbach,

1990). The plutons are all related directly to Jurassic volcanic activity in proximity of the north

American craton. Although the ages of the plutons appear to be getting younger further north in

the Wrangellia terrane (Sampson et al., 1990), they do not match up with the ages of the plutons

in the Seven Devils terrane or in the Blue Mountain Province, which are significantly younger

than the ages in the Wrangellia terrane.

Tectonic Implications

The Seven Devils terrane sits along the western boundary of the Salmon River suture

zone. This zone trends approximately N to NNE through much of western Idaho. The Salmon

River suture zone is characterized by a sharp isotopic transition known as the 0.706 87Sr/86Sr

line. This line represents the change from Precambrian North American basement in the east to

younger exotic terranes in the west (Gasching et al., 2011).

This line can be defined by other isotopic variations and by the general age of the rocks.

There is a significant difference between the Lu-Hf values from the Seven Devils terrane on the

western side of the suture zone and the Idaho Batholith on the eastern side of the suture zone.

The Idaho Batholith yields εHf values of -5 to -30 which is below the CHUR line indicating a

continentally derived terrane (Gasching et al., 2011). The εHf values of the Seven Devils terrane

range from 8.6 to 15.6. These values plot above the CHUR line and close to the depleted mantle

line. This means that the analyzed samples are derived from juvenile arc crust.

The surrounding terranes in the Blue Mountains Province and the Wrangellia terrane

have similar isotopic compositions that tell the same story of a juvenile arc crust. The studies

40

done on these terranes use whole rock Nd isotopic ratios or zircon Hf ratios. Late Jurassic 162 -

145 Ma Plutons from the Baker terrane in the Blue Mountains Province give εHf(t) values from

7.8 to 12.3 (Schwartz, 2011). εNd values were collected from the Olds Ferry terrane in the Blue

Mountains Province. The εNd values range from 3.06 to 6.92 for 121.72 - 173.91 Ma rocks

(Tumpane, 2010). The Wrangellia terrane provides εNd values of 2.9 to 5.6 for igneous and

plutonic rocks from the late Jurassic to the early Permian (Samson et al., 1990). While the range

of isotopic values from the Wrangellia terrane show a juvenile arc setting, the ages from the

granodioritic plutons are much older than those of the Seven Devils terrane. The age pattern of

the Wrangellia terrane starting with the oldest to the south, excluding the Seven Devils terrane,

and the youngest in the north would not work with the ages of the Seven Devils terrane or the

Baja B.C. hypothesis of terrane transport if these two terranes belonged together.

The Seven Devils terrane has a similar tectonic setup as the Coast Mountains Batholith in

western Canada. Both the Seven Devils terrane and the Coast Mountains Batholith are

considered a part of a group of terranes or a group of terranes respectively. They both sit along

shear zones and the terranes are divided by faulting. The εHf(t) values from the Seven Devils

samples come out to be very similar to the values of the plutons in the Stikine terrane which are

also juvenile arc derived in the Coast Mountains Batholith as seen in Fig. 8. The average values

for the Seven Devils terrane plutons sit between 10 and 11 which are similar to the 10 to 13

values for Hf in the plutons in the Stikine terrane (Cecil et al., 2011). To have such a juvenile

crustal signature, the crust under the Seven Devils terrane had to have been of a juvenile oceanic

arc origin. It also had not only partial crustal remelting, but also an incorporation of mantle-

derived basalts from the subducting slab. The sharp shear zone boundary, as opposed to

41

overthrusting the terrane on the continent, allowed the Seven Devils terrane to keep its sharp

contrasting isotopic values as opposed to a gradual shift to a continental signature.

The Seven Devils terrane shows a juvenile crustal signature in the intermediate intrusive

rocks. The ages collected range from 136.7 to 120.0 Ma. Ages from previously dated plutons

from the Blue Mountains Province suggest timing of thrusting in the Salmon River suture zone

began somewhere around 135 to 130 Ma (Schwartz et al., 2011; Snee et al., 1995). The isotopic

compositions suggest that the plutons were emplaced before the complete collision and

incorporation of continental crust in the melt.

Conclusions

Figure 8: Schematic cross section of the Coast Mountains batholiths (CMB) (from fig. 9 Cecil et al.,

2011). This shows the sharp contrast of the shear zone along with εHf(t) values of plutons in each

terrane.

42

The LA-ICPMS zircon U-Pb isotopic dating of the Seven Devils intrusive rocks yield a

crystallization age range of 136.7 to 120.0 Ma. The Lu-Hf isotopic data yields εHf(t) values from

8.6 to 15.6. This shows that the samples are from a young arc directly associated with the

depleted mantle values. These results suggest two separate things. The Seven Devils terrane can

not belong to the Wrangellia terrane due to the age discrepancies between them. The Seven

Devils terrane is similar to the terranes in the Blue Mountains Province based on similarly aged

plutons and isotopic data. Information on the isotopic composition of the terranes in the Blue

Mountains Province is still sparse and the addition of new data from each terrane would be

beneficial to make a direct comparison of all the terranes.

Acknowledgements: This work was funded by Submit funds from Dr. Kirsten Nicholson and

the Department of Geological Sciences at Ball State University in Muncie, Indiana.

References

Anderson, R. G., and Reichenback, I., 1990; Geochronometric (U-Pb and K-Ar) framework for

Jurassic (172-158 Ma) and Tertiary (46-27 Ma) plutons in Queen Charlotte Islands,

British Columbia: in Woodsworth, G. J., ed., Evolution and Petroleum Potential of the

Queen Charlotte Basin, British Columbia: Geol. Survey Canada Paper 90-10.

Armstrong, R. L., 1988, Mesozoic and early Cenozoic magmatic evolution of the Canadian

Cordillera: Geol. Soc. America Spec. Paper 218, p. 55-91.

Avé Lallemant, H.G., 1995, Pre-Cretaceous tectonic evolution of the Blue Mountains province,

northeastern Oregon, in Vallier, T.L., and Brooks, H.C., eds., Geology of the Blue

Mountains region of Oregon, Idaho, and Washington: U.S. Geological Survey

Professional Paper 1438, p. 271–304.

Brooks, H.C., 1979, Plate tectonics and the geologic history of the Blue Mountains, Oregon:

43

Oregon Geology, v. 41, no. 5, p. 71–80.

Burchfiel, B.C., Cowan, D.S., and Davis, G.A., 1992, Tectonic overview of the Cordilleran

orogen in the western United States, in Burchfi el, B.C., Lipman, P.C., and Zoback, M.L.,

eds., The Cordilleran orogen: Conterminous U.S.: Boulder, Colorado, Geological Society

of America, Geology of North America, v. G-3, p. 407–479.

Caruthers, A.H., Stanley, G.D., Jr., Blodgett, R.B., Katvala, E.C. 2005, Upper Triassic shallow-

water marine fauna from the Wrangellia and Alexander Terranes (Southern Alaska) and

their paleobiogeographic implications, Abstracts with Programs, Geological Society of

American 37: 42.

Champion, D. E., Howell, D. G., and Gramme, C. S., 1984, Paleomagnetic and geological data

indicating 2500 km of northward displacement for the Salinian and related terranes,

California: Journal of Geophysical Research, v. 89, p. 7736-7752.

Davidson, G.F., 1990, Cretaceous tectonic history along the Salmon River Suture Zone near

Orofino, Idaho; metamorphic, structural, and 40Ar/39Ar thermochronologic constraints:

Oregon State University, M.S. thesis, 143 p.

Dickinson, W.R., 2004. Evolution of the North American Cordillera: Annual Review of Earth

and Planetary Sciences 32: 13–45.

Ferns, M.L., and Brooks, H.C., 1995, The Bourne and Greenhorn subterranes of the Baker

terrane, northeastern Oregon: Implications for the evolution of the Blue Mountains

island-arc system: U.S. Geological Survey Professional Paper 1438, p. 331–358.

Gasching, Richard M., Vervoort, Jeffrey D., Lewis, Reed S., Tikoff, Basil, 2011, Isotopic

Evolution of the Idaho Batholith and Challis Intrusive Province, Northern US Cordillera,

Journal of Petrology, Vol 52, No. 12, pp 2397-2429.

44

Gehrels, G.E., Valencia, V., Ruiz, J., 2008, Enhanced precision, accuracy, efficiency, and spatial

resolution of U-Pb ages by laser ablation–multicollector–inductively coupled plasma–

mass spectrometry: Geochemistry, Geophysics, Geosystems, v. 9, Q03017.

Gehrels, G.E., Valencia, V., Pullen, A., 2006, Detrital zircon geochronology by Laser-Ablation

Multicollector ICPMS at the Arizona LaserChron Center, in Loszewski, T., and Huff, W.,

eds., Geochronology: Emerging Opportunities, Paleontology Society Short Course:

Paleontology Society Papers, v. 11, 10 p.

Gehrels, G. and Pecha, M., 2014, Detrital zircon U-Pb geochronology and Hf isotope

geochemistry of Paleozoic and Triassic passive margin strata of western North America:

Geosphere, v. 10 (1), p. 49-65.

Gray, K.D., 2013, Structure of the Arc-Continent Transition in the Riggins Region of West-

Central Idaho: Strip Maps and Structural Sections: Idaho Geological Survey Technical

Report 13-1, scale 1:24,000, 2 plates.

Gray, Keith D., Oldow, John S., 2005 Contrasting structural histories of the Salmon River belt

and Wallowa terrane: Implications for terrane accretion in northeastern Oregon and west-

central Idaho, GSA Bulletin; v. 117; no. 5/6; p. 687–706.

Hamilton, W., 1963, Metamorphism in the Riggins region, western Idaho: U.S. Geological

Survey Professional Paper 436, 95 p.

Harbert, H., Hillhouse, J.W., and Vallier, T.L., 1995, Paleomagnetism of the Permian Wallowa

terrane: Implications for the terrane migration and orogeny: Journal of Geophysical

Research: v.100, p. 12,573-12,588.

Hillhouse, J.W., Grommé, S. and Vallier, T.L., 1982, Paleomagnetism and Mesozoic tectonics of

45

the Seven Devils Volcanic Arc in Northeastern Oregon: Journal of Geophysical

Research: v. 87, p. 3777-3794.

Hillhouse, J.W., Gromme, C.S., 1984, Northward displacement and accretion of Wrangellia; new

paleomagnetic evidence from Alaska, Journal of Geophysical Research 89: 4461-4477.

Jones, D.L., Silberling, N.J., and Hillhouse, J.W., 1977, Wrangellia—A displaced terrane in

northwestern North America: Canadian Journal of Earth Sciences, v. 14, p. 2565–2577.

Kalk, Michael Liam., 2008 "Revisiting the Seven Devils-Wrangellia connection: the

paleogeography of triassic rocks in western Idaho." WWU Masters Thesis Collection.

348.

Košler, J., and Sylvester, P.J., 2003, Present Trends and the Future of Zircon in Geochronology:

Laser Ablation ICPMS: Reviews in Mineralogy and Geochemistry, v. 53, p. 243-275.

Kurz, Gene A., 2010, Geochemical, Isotopic, and U-Pb Geochronologic Investigations of

Intrusive Basement Rocks from the Wallowa and Olds Ferry Arc Terranes, Blue

Mountains Province, Oregon-Idaho, Boise State University, dissertation.

Kurz, Gene A., Schmitz, Mark D., Northrup, Clyde J., Vallier, Tracy L., 2016, Isotopic

compositions of intrusive rocks from the Wallowa and Olds Ferry arc terranes of

northeastern Oregon and western Idaho: Implications for Cordilleran evolution,

lithospheric structure, and Miocene magmatism, Lithosphere; v. 9; no. 2; p. 235–264.

LaMaskin, Todd A., Dorsey, Rebecca J., Vervoort, Jeffrey D., 2008, Tectonic Controls on

Mudrock Geochemistry, Mesozoic Rocks of Eastern Oregon and Western Idaho, U.S.A.:

Implications for Cordilleran Tectonics, Journal of Sedimentary Research, v. 78, 765–783

DOI: 10.2110/jsr.2008.087.

LaMaskin, Todd A., Vervoort, Jeffrey D., Dorsey, Rebecca J., Wright, James E., 2011, Early

46

Mesozoic paleogeography and tectonic evolution of the western United States: Insights

from detrital zircon U-Pb geochronology, Blue Mountains Province, northeastern

Oregon, GSA Bulletin; v. 123; no. 9/10; p. 1939–1965; doi: 10.1130/B30260.1.

LaMaskin, Todd A., Dorsey, Rebecca J., Vervoort, Jeffrey D., Schmitz, Mark D., Tumpane, Kyle

P., Moore, Nicholas O., 2015, Westward Growth of Laurentia by Pre–Late Jurassic

Terrane Accretion, Eastern Oregon and Western Idaho, United States, The Journal of

Geology, volume 123, p. 233–267.

McClelland, W.C., Tikoff, B., and Manduca, C.A., 2000, Two-phase evolution of accretionary

margins; examples from the North American Cordillera: Tectonophysics, v. 326, no. 1-2,

p. 37-55.

Murphy, J. B., Nance, R. D., & Cawood, P. A., 2009, Contrasting modes of supercontinent

formation and the conundrum of Pangea. Gondwana Research, 15(3-4), 408–420.

Plafker, G., Nokleberg, W.J., Lull, J.S., 1989, Bedrock geology and tectonic evolution of the

Wrangellia, Peninsular, and Chugach terranes along the Trans-Alaska Crustal Transect in

the Chugach Mountains and southern Copper River basin, Alaska, Journal of

Geophysical Research, B, Solid Earth and Planets 94: 4255-4295.

Samson, Scott D., Patchett, P. Jonathan, Gehrels, George E., Anderson, Robert G., 1990, Nd and

Sr Isotopic Characterization of the Wrangellia Terrane and Implications for Crustal

Growth of the Canadian Cordillera, The Journal of Geology, Vol. 98, No. 5, pp. 749-762.

Sarewitz, D. R., 1982. Geology of a part of the Heavens Gate quadrangle, Seven Devils

Mountains, western Idaho.

Sarewitz, D., 1983, Seven Devils terrane; is it really a piece of Wrangellia? Geology Boulder

11: 634-637.

47

Schwartz, Joshua J., Johnson, Kenneth, Miranda, Elena A., Wooden, Joseph L., 2011, The

generation of high Sr/Y plutons following Late Jurassic arc–arc collision, Blue

Mountains province, NE Oregon, Lithos 126, pp 22–41.

Sigloch, K., Mihalynuk, M.G., 2013, Intra-oceanic subduction shaped the assembly of

Cordilleran North America, Nature, Vol. 496, pp 50-56.

Snee, L.W., Lund, K., Sutter, J.F., Balcer, D.E., and Evans, K.V., 1995, An 40Ar/39Ar chronicle

of the tectonic development of the Salmon River suture zone, western Idaho, in Vallier,

T.L., and Brooks, H.C., eds., Geology of the Blue Mountains region of Oregon, Idaho,

and Washington: U.S. Geological Survey Professional Paper 1438, 56 p.

Strayer, L.M., Hyndman, D.W., Sears, J.W., and Myers, P.E., 1989, Direction and shear sense

during suturing of the Seven Devils-Wallowa terrane against North America in western

Idaho: Geology, v. 17, p. 1025-1028.

Tumpane, Kyle P., 2010, Age and Isotopic Investigations of the Olds Ferry Terrane and its

Relations to Other Terranes of the Blue Mountains Province, Eastern Oregon and West-

Central Idaho, Boise State University Masters Thesis Collection.

Umhoefer, P.J., 1987, Northward translation of “BAJA British Columbia” along the Late

Cretaceous to Paleocene margin of western North America, Tectonics, Volume 6, Issue 4,

p. 377-394.

Vallier, T.L., 1977, The Permian and Triassic Seven Devils Group, western Idaho and

northeastern Oregon: U.S. Geological Survey Bulletin 1437, p. 58.

Vallier, T.L., and Brooks, H.C., 1986, Geologic implications of Paleozoic and Mesozoic

48

paleontology and biostratigraphy, Blue Mountains province, Oregon and Idaho, in

Vallier, T.L., and Brooks, H.C., eds., Geology of the Blue Mountains region of Oregon,

Idaho, and Washington: U.S. Geological Survey Professional Paper 1435, p. 65–78.

Vallier, T.L., 1995, Petrology of pre-Tertiary igneous rocks in the Blue Mountains region of

Oregon, Idaho, and Washington; implications for the geologic evolution of a complex

island arc, U.S. Geological Survey Professional Paper P1438: 125-209.

Vallier, T., (1998) Islands and Rapids: A geologic story of Hells Canyon, Confluence Press,

Lewiston, ID, 151 pp.

Vallier, T.L, Schmidt, K.L., LaMaskin, T.A., 2016, Geology of the Wallowa terrane, Blue

Mountains province, in the northern part of Hells Canyon, Idaho, Washington, and

Oregon, Geological Society of America Field Guide 41, p. 211–249,

doi:10.1130/2016.0041(07).

Walker, N.W., 1986, U-Pb geochronologic and petrologic studies of the Blue Mountains terrane,

northeastern Oregon and west-central Idaho—Implications for pre-Tertiary tectonic

evolution [Ph.D. thesis]: Santa Barbara, University of California, 224 pp.

Wyld, S.J. and Wright, J.E., 2001, New evidence for Cretaceous strike-slip faulting in the U.S.

Cordillera; and implications for terrane displacement, deformation patterns and

plutonism: American Journal of Science, v. 301, p. 150-181.

Wyld, S.J., Umhoefer, P.J., Wright, J.E., 2006, Reconstructing northern Cordilleran terranes

along known Cretaceous and Cenozoic strike-slip faults: Implications for the Baja British

Columbia hypothesis and other models in Haggart, J.W., Enkin, R.J. and Monger,

J.W.H., eds., Paleogeography of the North American Cordillera: Evidence For and

49

Against Large-Scale Displacements: Geological Association of Canada, Special Paper

46, p. 277-298.

Wynne, P.J., Irving, E., Maxson, J.A. and Kleinspehn, K.L., 1995, Paleomagnetism of the Upper

Cretaceous strata of Mount Tatlow: Evidence for 3000 km of northward displacement of

the eastern Coast belt, British Columbia: Journal of Geophysical Research, v. 100, p.

6073-6091.

Acknowledgements

I would like to thank Kirsten Nicholson, my thesis advisor, for all her help and guidance.

I would also like to thank Shawn Malone and Klaus Neuman for all their help and advice along

the way. Special thanks to Mike Kutis and Eric Lange for teaching me how to use all the

machines that were crucial to the completion of this thesis.

I would like to thank all my peers for their help and support during the research process

and writing process of my thesis. I would like to thank Isaac Burton for helping in my field

excursion to collect rock samples. I would like to thank Josh Klier for all his help in processing

samples to collect zircons for analysis. I would also like to thank Adel Farag for help teaching

me the process of making thin sections.

I thank University of Arizona LaserChron lab for all their help and patience in showing

us how to use the LA-ICPMS and taking cathodoluminescence pictures of our zircons and

analyzing our samples for ages and Lu-Hf.

I would like to finally thank my parents, Ron and Teresa, and sister, Andie for all their

love and support throughout this process.

50

References

Anderson, R. G., and Reichenback, I., 1990; Geochronometric (U-Pb and K-Ar) framework for

Jurassic (172-158 Ma) and Tertiary (46-27 Ma) plutons in Queen Charlotte Islands,

British Columbia: in Woodsworth, G. J., ed., Evolution and Petroleum Potential of the

Queen Charlotte Basin, British Columbia: Geol. Survey Canada Paper 90-10.

Armstrong, R. L., 1988, Mesozoic and early Cenozoic magmatic evolution of the Canadian

Cordillera: Geol. Soc. America Spec. Paper 218, p. 55-91.

Avé Lallemant, H.G., 1995, Pre-Cretaceous tectonic evolution of the Blue Mountains province,

northeastern Oregon, in Vallier, T.L., and Brooks, H.C., eds., Geology of the Blue

Mountains region of Oregon, Idaho, and Washington: U.S. Geological Survey

Professional Paper 1438, p. 271–304.

Brooks, H.C., 1979, Plate tectonics and the geologic history of the Blue Mountains, Oregon:

Oregon Geology, v. 41, no. 5, p. 71–80.

Burchfi el, B.C., Cowan, D.S., and Davis, G.A., 1992, Tectonic overview of the Cordilleran

51

orogen in the western United States, in Burchfi el, B.C., Lipman, P.C., and Zoback, M.L.,

eds., The Cordilleran orogen: Conterminous U.S.: Boulder, Colorado, Geological Society

of America, Geology of North America, v. G-3, p. 407–479.

Caruthers, A.H., Stanley, G.D., Jr., Blodgett, R.B., Katvala, E.C. 2005, Upper Triassic shallow-

water marine fauna from the Wrangellia and Alexander Terranes (Southern Alaska) and

their paleobiogeographic implications, Abstracts with Programmes, Geological Society of

American 37: 42.

Cecil, M.R., Gehrels, G., Ducea, M.N., Patchett, P.J., 2011, U-Pb-Hf characterization of the

central Coast Mountains batholith: Implications for petrogenesis and crustal architecture,

Lithosphere, v. 3; no. 4; p. 247-260.

Champion, D. E., Howell, D. G., and Gramme, C. S., 1984, Paleomagnetic and geological data

indicating 2500 km of northward displacement for the Salinian and related terranes,

California: Journal of Geophysical Research, v. 89, p. 7736-7752.

Davidson, G.F., 1990, Cretaceous tectonic history along the Salmon River Suture Zone near

Orofino, Idaho; metamorphic, structural, and 40Ar/39Ar thermochronologic constraints:

Oregon State University, M.S. thesis, 143 pp.

Dickinson, W.R., 2004. Evolution of the North American Cordillera: Annual Review of Earth

and Planetary Sciences 32: 13–45.

Farag, Adel, 2018, Evaluation of Geochemical Characterizations and Petrographic Analysis of

the Permian-Triassic Seven Devils Group, West –Central Idaho, Ball State University,

Unpublished Master’s Thesis.

Ferns, M.L., and Brooks, H.C., 1995, The Bourne and Greenhorn subterranes of the Baker

52

terrane, northeastern Oregon: Implications for the evolution of the Blue Mountains

island-arc system: U.S. Geological Survey Professional Paper 1438, p. 331–358.

Gasching, Richard M., Vervoort, Jeffrey D., Lewis, Reed S., Tikoff, Basil, 2011, Isotopic

Evolution of the Idaho Batholith and Challis Intrusive Province, Northern US Cordillera,

Journal of Petrology, Vol 52, No. 12, pp. 2397-2429.

Gehrels, G.E., Valencia, V., Ruiz, J., 2008, Enhanced precision, accuracy, efficiency, and spatial

resolution of U-Pb ages by laser ablation–multicollector–inductively coupled plasma–

mass spectrometry: Geochemistry, Geophysics, Geosystems, v. 9, Q03017.

Gehrels, G.E., Valencia, V., Pullen, A., 2006, Detrital zircon geochronology by Laser-Ablation

Multicollector ICPMS at the Arizona LaserChron Center, in Loszewski, T., and Huff, W.,

eds., Geochronology: Emerging Opportunities, Paleontology Society Short Course:

Paleontology Society Papers, v. 11, 10 pp.

Gehrels, G. and Pecha, M., 2014, Detrital zircon U-Pb geochronology and Hf isotope

geochemistry of Paleozoic and Triassic passive margin strata of western North America:

Geosphere, v. 10 (1), p. 49-65.

Gray, K.D., 2013, Structure of the Arc-Continent Transition in the Riggins Region of West-

Central Idaho: Strip Maps and Structural Sections: Idaho Geological Survey Technical

Report 13-1, scale 1:24,000, 2 plates.

Gray, Keith D., Oldow, John S., 2005 Contrasting structural histories of the Salmon River belt

and Wallowa terrane: Implications for terrane accretion in northeastern Oregon and west-

central Idaho, GSA Bulletin; v. 117; no. 5/6; p. 687–706.

Hamilton, W., 1963, Metamorphism in the Riggins region, western Idaho: U.S. Geological

Survey Professional Paper 436, 95 p.

53

Harbert, H., Hillhouse, J.W., and Vallier, T.L., 1995, Paleomagnetism of the Permian Wallowa

terrane: Implications for the terrane migration and orogeny: Journal of Geophysical

Research: v.100, p. 12,573-12,588.

Hillhouse, J.W., Grommé, S. and Vallier, T.L., 1982, Paleomagnetism and Mesozoic tectonics of

the Seven Devils Volcanic Arc in Northeastern Oregon: Journal of Geophysical

Research: v. 87, p. 3777-3794.

Hillhouse, J.W., Gromme, C.S., 1984, Northward displacement and accretion of Wrangellia; new

paleomagnetic evidence from Alaska, Journal of Geophysical Research 89: 4461-4477.

Jones, D.L., Silberling, N.J., and Hillhouse, J.W., 1977, Wrangellia—A displaced terrane in

northwestern North America: Canadian Journal of Earth Sciences, v. 14, p. 2565–2577.

Kalk, Michael Liam., 2008 "Revisiting the Seven Devils-Wrangellia connection: the

paleogeography of triassic rocks in western Idaho." WWU Masters Thesis Collection.

348 pp.

Košler, J., and Sylvester, P.J., 2003, Present Trends and the Future of Zircon in Geochronology:

Laser Ablation ICPMS: Reviews in Mineralogy and Geochemistry, v. 53, p. 243-275.

Kurz, Gene A., 2010, Geochemical, Isotopic, and U-PB Geochronologic Investigations of

Intrusive Basement Rocks from the Wallowa and Olds Ferry Arc Terranes, Blue

Mountains Province, Oregon-Idaho, Boise State University, dissertation.

Kurz, Gene A., Schmitz, Mark D., Northrup, Clyde J., Vallier, Tracy L., 2016, Isotopic

compositions of intrusive rocks from the Wallowa and Olds Ferry arc terranes of

northeastern Oregon and western Idaho: Implications for Cordilleran evolution,

lithospheric structure, and Miocene magmatism, Lithosphere; v. 9; no. 2; p. 235–264.

LaMaskin, Todd A., Dorsey, Rebecca J., Vervoort, Jeffrey D., 2008, Tectonic Controls on

54

Mudrock Geochemistry, Mesozoic Rocks of Eastern Oregon and Western Idaho, U.S.A.:

Implications for Cordilleran Tectonics, Journal of Sedimentary Research, v. 78, 765–783

DOI: 10.2110/jsr.2008.087.

LaMaskin, Todd A., Vervoort, Jeffrey D., Dorsey, Rebecca J., Wright, James E., 2011, Early

Mesozoic paleogeography and tectonic evolution of the western United States: Insights

from detrital zircon U-Pb geochronology, Blue Mountains Province, northeastern

Oregon, GSA Bulletin; v. 123; no. 9/10; p. 1939–1965; doi: 10.1130/B30260.1.

LaMaskin, Todd A., Dorsey, Rebecca J., Vervoort, Jeffrey D., Schmitz, Mark D., Tumpane, Kyle

P., Moore, Nicholas O., 2015, Westward Growth of Laurentia by Pre–Late Jurassic

Terrane Accretion, Eastern Oregon and Western Idaho, United States, The Journal of

Geology, volume 123, p. 233–267.

Lange, Eric S., 2014, Geochemistry of the North Cape Mafic-Ultramafic Complex: An Arc-

Type Primitive Magma Intrusion, Northeasternmost New Zealand, Ball State University,

Masters Thesis.

Ludwig, K.R., 2008, Isoplot 3.60. Berkeley Geochronology Center, Special Publication No. 4, p.

77.

McClelland, W.C., Tikoff, B., and Manduca, C.A., 2000, Two-phase evolution of accretionary

margins; examples from the North American Cordillera: Tectonophysics, v. 326, no. 1-2,

p. 37-55.

Mueller, P., Kamenov, G., Heatherington, A., Richards, J., 2008. Crustal evolution in the

southern Appalachian orogen: evidence from Hf isotopes in detrital zircons. Journal of

Geology 116, 414–422.

Murphy, J. B., Nance, R. D., & Cawood, P. A., 2009, Contrasting modes of supercontinent

55

formation and the conundrum of Pangea. Gondwana Research, 15(3-4), 408–420.

Pearce, Julian A., Harris, Nigel BW, Tindle, Andrew G., 1984, Trace element discrimination

diagrams for the tectonic interpretation of granitic rocks, Journal of petrology 25.4, pp.

956-983.

Plafker, G., Nokleberg, W.J., Lull, J.S., 1989, Bedrock geology and tectonic evolution of the

Wrangellia, Peninsular, and Chugach terranes along the Trans-Alaska Crustal Transect in

the Chugach Mountains and southern Copper River basin, Alaska, Journal of

Geophysical Research, B, Solid Earth and Planets 94: 4255-4295.

Samson, Scott D., Patchett, P. Jonathan, Gehrels, George E., Anderson, Robert G., 1990, Nd and

Sr Isotopic Characterization of the Wrangellia Terrane and Implications for Crustal

Growth of the Canadian Cordillera, The Journal of Geology, Vol. 98, No. 5, pp. 749-762

Sarewitz, D. R., 1982. Geology of a part of the Heavens Gate quadrangle, Seven Devils

Mountains, western Idaho.

Sarewitz, D., 1983, Seven Devils terrane; is it really a piece of Wrangellia? Geology Boulder

11: 634-637.

Scherer, E., Münker, C., and Mezger, K., 2001, Calibration of the Lutetium-Hafnium Clock:

Science, v. , p. 683–687.

Schwartz, Joshua J., Johnson, Kenneth, Miranda, Elena A., Wooden, Joseph L., 2011, The

generation of high Sr/Y plutons following Late Jurassic arc–arc collision, Blue

Mountains province, NE Oregon, Lithos 126, pp 22–41.

Sigloch, K., Mihalynuk, M.G., 2013, Intra-oceanic subduction shaped the assembly of

Cordilleran North America, Nature, Vol. 496, pp 50-56.

Snee, L.W., Lund, K., Sutter, J.F., Balcer, D.E., and Evans, K.V., 1995, An 40Ar/39Ar chronicle

56

of the tectonic development of the Salmon River suture zone, western Idaho, in Vallier,

T.L., and Brooks, H.C., eds., Geology of the Blue Mountains region of Oregon, Idaho,

and Washington: U.S. Geological Survey Professional Paper 1438, 56 pp.

Söderlund, U., Patchett, P.J., Vervoort, J.D., and Isachsen, C.E., 2004, The 176Lu decay constant

determined by Lu-Hf and U-Pb isotope systematics of Precambrian mafic intrusions:

Earth and Planetary Science Letters, v. 219, p. 311-324.

Strayer, L.M., Hyndman, D.W., Sears, J.W., and Myers, P.E., 1989, Direction and shear sense

during suturing of the Seven Devils-Wallowa terrane against North America in western

Idaho: Geology, v. 17, p. 1025-1028.

Tumpane, Kyle P., 2010, Age and Isotopic Investigations of the Olds Ferry Terrane and its

Relations to Other Terranes of the Blue Mountains Province, Eastern Oregon and West-

Central Idaho, Boise State University Masters Thesis Collection.

Umhoefer, P.J., 1987, Northward translation of “BAJA British Columbia” along the Late

Cretaceous to Paleocene margin of western North America, Tectonics, Volume 6, Issue 4,

p. 377-394.

Vallier, T.L., 1977, The Permian and Triassic Seven Devils Group, western Idaho and

northeastern Oregon: U.S. Geological Survey Bulletin 1437, p. 58.

Vallier, T.L., and Brooks, H.C., 1986, Geologic implications of Paleozoic and Mesozoic

paleontology and biostratigraphy, Blue Mountains province, Oregon and Idaho, in

Vallier, T.L., and Brooks, H.C., eds., Geology of the Blue Mountains region of Oregon,

Idaho, and Washington: U.S. Geological Survey Professional Paper 1435, p. 65–78.

Vallier, T.L., 1995, Petrology of pre-Tertiary igneous rocks in the Blue Mountains region of

57

Oregon, Idaho, and Washington; implications for the geologic evolution of a complex

island arc, U.S. Geological Survey Professional Paper P1438: 125-209.

Vallier, T., (1998) Islands and Rapids: A geologic story of Hells Canyon, Confluence Press,

Lewiston, ID, 151 pp.

Vallier, T.L, Schmidt, K.L., LaMaskin, T.A., 2016, Geology of the Wallowa terrane, Blue

Mountains province, in the northern part of Hells Canyon, Idaho, Washington, and

Oregon, Geological Society of America Field Guide 41, p. 211–249,

doi:10.1130/2016.0041(07).

Walker, N.W., 1986, U-Pb geochronologic and petrologic studies of the Blue Mountains terrane,

northeastern Oregon and west-central Idaho—Implications for pre-Tertiary tectonic

evolution [Ph.D. thesis]: Santa Barbara, University of California, 224 pp.

Winchester, J. A., and P. A. Floyd. 1977, Geochemical discrimination of different magma series

and their differentiation products using immobile elements, Chemical geology 20: 325-

343.

Wyld, S.J. and Wright, J.E., 2001, New evidence for Cretaceous strike-slip faulting in the U.S.

Cordillera; and implications for terrane displacement, deformation patterns and

plutonism: American Journal of Science, v. 301, p. 150-181.

Wyld, S.J., Umhoefer, P.J., Wright, J.E., 2006, Reconstructing northern Cordilleran terranes

along known Cretaceous and Cenozoic strike-slip faults: Implications for the Baja British

Columbia hypothesis and other models in Haggart, J.W., Enkin, R.J. and Monger,

J.W.H., eds., Paleogeography of the North American Cordillera: Evidence for and

Against Large-Scale Displacements: Geological Association of Canada, Special Paper

46, p. 277-298.

58

Wynne, P.J., Irving, E., Maxson, J.A. and Kleinspehn, K.L., 1995, Paleomagnetism of the Upper

Cretaceous strata of Mount Tatlow: Evidence for 3000 km of northward displacement of

the eastern Coast belt, British Columbia: Journal of Geophysical Research, v. 100, p.

6073-6091.

59

Appendix

60

SD001

Fig. A-1 Sample SD001 is a basalt. Top

picture is the sample in plane polarized light

(PPL) and bottom picture is the sample in

cross polarized light (XPL). The scale bar

represents 1000 µm. Minerals present:

plagioclase that are very anhedral, some

massive up to 5 mm. Gray to white in color

in ppl; XPL—some have been replaced by or

have inclusions of clinopyroxene or

hornblende; intergranular texture; Oxides—

red brown color, very minimal;

Groundmass—appears to be glass or opaque

minerals; chlorite—not visible, but the rock

is definitely beat up and possibly slightly metamorphosed. Plagioclase takes up to 60% of the

rock. Clinopyroxene takes up 1% and hornblende is also 1%. The glass takes up to 38% of the

rock’s mass.

Plag.

Plag.

PPL

XPL

61

SD002

Fig. A-2 Sample SD002 is a granodiorite.

Samples are shown in PPL and XPL with

the scale bar of 1000 µm. Very aphanitic

with few slightly larger crystals present. The

larger crystals are light green in ppl and

dark gray with a mix of 2nd order colors in

cross polarized light. The minerals that are

subhedral to anhedral are hornblende. The

groundmass appears to be all

microcrystalline plagioclase and quartz with

some clinopyroxene or hornblende

intermixed. Chlorite appears to be altering

the larger minerals. Plagioclase makes up

80% of the rock. Hornblende makes up 18%. Chlorite makes up 1% and opaque minerals make

up 1%.

Hbl

Hbl

Plag.

Plag.

XPL

PPL

62

SD003

Fig. A-3 Sample SD003 is metamorphosed the most. The top images are in PPL and the bottom

in XPL with a scale of 1000 µm. The largest minerals are white in ppl and show some twinning

in XPL like plagioclase. The groundmass is brown in PPL and in XPL. It also shows few

portions of higher order oranges and pinks. There are circular pockets of an unknown mineral

that appears to be aphanitic. The mineral could be clinopyroxene, or hornblende. Spherulites are

spots where fibrous crystals radially grow from a nucleation point, usually during strong

supercooling of the magmatic liquid. The circular texture is from the rugose corals that could

have been incorporated as the material flowed over it.

Plag.

Plag.

R. Coral

R. Coral

PPL PPL

XPL XPL

63

SD004

Fig. A-4 Sample SD004 is diorite with a

porphyritic texture. The scale is 1000 µm. The

groundmass is made up of microcrystalline

plagioclase and quartz. Plagioclase is clear with

low relief and lacks a euhedral shape in PPL.

There are needle-like minerals that are faintly

pleochroic from green to yellow in PPL. These

minerals are chlorite. In XPL they are green

anomalous interference colors. Hornblende is

euhedral to subhedral in shape and is

hydrothermally altered to some clay minerals,

prehnite, and possibly some carbonate mineral

like calcite. Mineral percentages are plagioclase 60% hornblende 25%, Chlorite 8%, Quartz 5%,

Carbonate minerals 2%

Hbl

Hbl Chl

Chl

PPL

XPL

64

SD005

Fig. A-5 Sample SD005 is a diorite. Scale

bar shows 1000 µm. Thin section is a little

thick. Biotite—light brown to dark brown

and black in PPL (pleochroism). Brownish

orange in cross polarized light. Chlorite—

green in PPL that is light to medium green.

In XPL it has multiple colors. Quartz—

possible quartz is clear in ppl and appears to

not have any cleavage. In XPL it is a higher

order than normal because the slid is thick.

Plagioclase—clear in ppl. White to yellow

black in XPL. Has oscillatory zoning.

Hornblende—clear in ppl and in xpl has 2rd

order colors. Plagioclase makes up 75% of the rock. Hornblende makes up 20%. Quartz makes

up 1% of the rock. Biotite makes up 2%. Finally, chlorite takes up 1% of the rock.

Bt

Bt

Plag.

Plag.

Qtz

Qtz

PPL

XPL

65

SD006

Fig. A-6 Sample SD006 is a diorite with a

phaneritic texture. This thin section is a

little thick. The scale bar shows 1000 µm.

Large crystals of plagioclase with

oscillatory zoning and twinning. The

plagioclase zoning appears to be in a spiral

motion. Even more massive crystals of

biotite. Biotite is pleochroic from dark

brown to light brown with a tint of green.

Chlorite is visible replacing some of the

biotite. It is green to light tan in color in

PPL. Hornblende is green to brown in PPL.

They have euhedral shapes.

Bt

Bt

Plag.

Plag.

Hbl.

Hbl.

XPL

PPL

66

SD007

Fig. A-7 Sample SD007 is a syenitic

diorite. Chlorite visible alteration as green

in PPL. Hornblende and plagioclase

present. Hornblende and plagioclase are

large crystals in an aphanitic groundmass.

Plagioclase has distinct zoning.

Hornblende is altered to chlorite and clay

minerals. Quartz is visible as some larger

crystals but mostly remain in the

groundmass. The groundmass is

microcrystalline plagioclase and quartz.

The thin section is a bit too thick showing

higher interference colors for some

minerals. Plagioclase makes up 80% of the rock. Hornblende takes up to 15% of the rock.

Chlorite is seen as 2% of the rock. Quartz is 2% of the rock. Opaques are in 1% of the rock.

Plag.

Plag.

Hbl.

PPL

XPL

Hbl.

Cl

Cl Qtz

Qtz

67

SD008

Fig A-8 Sample SD008 is porphyritic

granodiorite. The scale bar is 1000 µm and

the sample is a bit thick. There are a few

larger crystals of plagioclase, quartz, and

hornblende. Small crystals of chlorite

scatter the thin section. There is also a

combination of pumpellyite and prehnite

scattered throughout the thin section. There

is microcrystalline plagioclase and quartz in

the groundmass. There are a few larger

crystals of quartz in the thin section, but

they are rare. Plagioclase makes up 75% of

the rock. Hornblende makes up 20%. Quartz

makes up 2%. Chlorite makes up 1%, clays make up 1%, and opaque minerals make up 1%.

Plag.

Plag.

Qtz.

Qtz.

Chl.

Chl.

PPL

XPL

Pmp

Pmp

68

SD009

Fig A-9 Sample SD009 is a syenitic diorite

with a porphyritic texture. The scale is

1000 µm and the top image is in PPL and

the bottom is in XPL. Appears to be all

microcrystalline plagioclase and quartz in

the groundmass. The larger crystals are

hornblende and plagioclase. There are

some iron oxides and visible weathering of

the sample. The large plagioclase crystal

has a poikilitic texture with an unknown

mineral. The hornblende crystals are fairly

small and unaltered by chlorite. The rock

looks like it is mostly plagioclase at 90%.

Hornblende makes up 5%. The unknown minerals in the plagioclase take up 3%, and the

opaques take up 2% of the rock.

Plag.

Plag.

PPL

XPL

69

Table A-1: U-Pb dating and of zircons from this study using LA-ICP-MS

Isotope ratios Apparent ages (Ma)

Analysis U 206Pb U/Th Th/U 206Pb* ± 207Pb* ± 206Pb* ± error 206Pb* ± 207Pb* ± 206Pb* ± Best age ± Conc

(ppm) 204Pb 207Pb* (%) 235U* (%) 238U (%) corr. 238U* (Ma) 235U (Ma) 207Pb* (Ma) (Ma) (Ma) (%)

SD004 Spot 1 58 18796 2.3 0.43 21.4316 2.9 0.1403 3.1 0.0218 1.0 0.32 139.1 1.4 133.3 3.9 30.8 70.7 139.1 1.4 NA

SD004 Spot 2 67 4766 2.3 0.44 21.1253 2.3 0.1395 2.6 0.0214 1.2 0.47 136.4 1.6 132.6 3.2 65.2 54.4 136.4 1.6 NA

SD004 Spot 3 40 9588 3.2 0.31 20.5105 2.9 0.1492 3.1 0.0222 1.1 0.36 141.6 1.6 141.2 4.1 135.1 68.9 141.6 1.6 NA

SD004 Spot 4 92 7366 2.1 0.47 20.6257 2.3 0.1401 2.5 0.0210 1.1 0.45 133.8 1.5 133.1 3.2 121.9 53.1 133.8 1.5 NA

SD004 Spot 5 96 12452 2.8 0.36 20.3165 1.8 0.1453 2.2 0.0214 1.2 0.57 136.6 1.7 137.7 2.8 157.4 41.5 136.6 1.7 NA

SD004 Spot 6 76 8014 4.1 0.24 20.5340 2.7 0.1414 2.9 0.0211 1.1 0.36 134.4 1.4 134.3 3.7 132.4 64.0 134.4 1.4 NA

SD004 Spot 7 120 10278 1.7 0.57 20.5869 1.8 0.1415 2.2 0.0211 1.2 0.55 134.8 1.6 134.3 2.8 126.3 43.4 134.8 1.6 NA

SD004 Spot 8 73 5316 3.6 0.28 20.9750 2.1 0.1374 2.4 0.0209 1.2 0.49 133.4 1.6 130.7 3.0 82.2 50.1 133.4 1.6 NA

SD004 Spot 9 40 3567 4.0 0.25 21.7734 2.9 0.1302 4.7 0.0206 3.7 0.78 131.3 4.8 124.3 5.5 NA NA 131.3 4.8 NA

SD004 Spot 10 40 11615 3.9 0.26 20.6791 3.0 0.1471 3.2 0.0221 1.0 0.32 140.7 1.4 139.3 4.2 115.8 71.8 140.7 1.4 NA

SD004 Spot 11 50 3588 3.6 0.28 21.7277 2.6 0.1396 2.8 0.0220 1.0 0.35 140.3 1.3 132.7 3.5 NA NA 140.3 1.3 NA

SD004 Spot 12 129 707289 1.8 0.56 20.9653 1.8 0.1373 2.1 0.0209 1.1 0.53 133.2 1.4 130.6 2.5 83.3 41.6 133.2 1.4 NA

SD004 Spot 13 115 16441 1.9 0.53 21.1707 1.6 0.1361 2.0 0.0209 1.1 0.57 133.4 1.5 129.5 2.4 60.1 38.8 133.4 1.5 NA

SD004 Spot 14 44 143364 4.2 0.24 21.0633 2.9 0.1420 3.2 0.0217 1.3 0.41 138.4 1.8 134.9 4.0 72.2 69.0 138.4 1.8 NA

SD004 Spot 15 73 8890 2.8 0.36 20.7969 2.5 0.1418 2.9 0.0214 1.5 0.50 136.5 2.0 134.7 3.7 102.4 59.2 136.5 2.0 NA

SD006 Spot 36 36 56698 3.2 0.31 20.3930 3.2 0.1331 3.5 0.0197 1.4 0.39 125.7 1.7 126.8 4.2 148.5 76.2 125.7 1.7 NA

SD006 Spot 37 29 2601 3.4 0.29 24.3319 6.4 0.1107 6.6 0.0195 1.3 0.20 124.7 1.6 106.6 6.6 NA NA 124.7 1.6 NA

SD006 Spot 38 40 8694 3.5 0.28 21.7980 2.8 0.1235 3.3 0.0195 1.7 0.51 124.7 2.1 118.3 3.6 NA NA 124.7 2.1 NA

SD006 Spot 39 21 5140 3.5 0.29 23.9783 4.1 0.1134 4.3 0.0197 1.6 0.36 125.9 1.9 109.0 4.5 NA NA 125.9 1.9 NA

SD006 Spot 40 114 115808 5.4 0.18 19.9518 1.8 0.1297 2.1 0.0188 1.0 0.49 119.9 1.2 123.8 2.5 199.6 42.9 119.9 1.2 NA

SD006 Spot 41 141 8050 3.7 0.27 21.4338 2.2 0.1181 2.4 0.0184 1.0 0.43 117.4 1.2 113.4 2.6 30.6 51.9 117.4 1.2 NA

SD006 Spot 42 67 6532 4.0 0.25 21.3004 2.9 0.1240 3.1 0.0192 1.0 0.33 122.3 1.3 118.7 3.5 45.5 70.4 122.3 1.3 NA

SD006 Spot 43 34 5315 3.8 0.27 20.7346 4.5 0.1297 4.6 0.0195 1.2 0.27 124.6 1.5 123.9 5.4 109.5 105.5 124.6 1.5 NA

SD006 Spot 44 266 10992 1.5 0.66 20.8326 1.2 0.1187 1.7 0.0179 1.2 0.70 114.7 1.3 113.9 1.8 98.3 28.4 114.7 1.3 NA

SD006 Spot 45 25 43376 2.8 0.35 19.4151 3.3 0.1396 3.6 0.0197 1.3 0.37 125.5 1.7 132.7 4.5 262.6 76.4 125.5 1.7 NA

SD006 Spot 46 48 25074 3.5 0.28 20.8851 2.6 0.1284 2.8 0.0195 1.1 0.40 124.3 1.4 122.7 3.3 92.4 62.0 124.3 1.4 NA

SD006 Spot 47 32 12015 2.9 0.34 21.4563 3.7 0.1272 3.9 0.0198 1.1 0.28 126.4 1.4 121.6 4.4 28.1 88.6 126.4 1.4 NA

SD006 Spot 48 71 15305 3.7 0.27 20.8781 2.6 0.1264 2.9 0.0191 1.2 0.43 122.3 1.5 120.9 3.3 93.1 62.6 122.3 1.5 NA

SD006 Spot 49 53 74963 3.8 0.26 21.0491 3.0 0.1250 3.3 0.0191 1.3 0.39 121.9 1.5 119.6 3.7 73.8 72.0 121.9 1.5 NA

SD006 Spot 50 25 9444 2.4 0.42 17.2176 3.8 0.1565 4.2 0.0196 1.6 0.39 124.8 2.0 147.7 5.7 531.9 84.1 124.8 2.0 NA

SD007 Spot 1 140 49829 2.0 0.49 20.1572 2.6 0.1269 2.9 0.0186 1.4 0.47 118.5 1.6 121.3 3.3 175.7 59.6 118.5 1.6 NA

SD007 Spot 2 103 14972 3.4 0.29 20.7581 1.8 0.1245 2.1 0.0187 1.0 0.48 119.7 1.2 119.1 2.3 106.8 42.7 119.7 1.2 NA

SD007 Spot 3 68 7944 4.4 0.23 20.7476 2.7 0.1271 2.8 0.0191 1.0 0.34 122.2 1.2 121.5 3.2 108.0 62.9 122.2 1.2 NA

SD007 Spot 4 153 26924 5.9 0.17 20.5005 1.4 0.1249 1.8 0.0186 1.1 0.64 118.6 1.3 119.5 2.0 136.2 31.7 118.6 1.3 NA

SD007 Spot 5 72 3855 5.1 0.19 21.4698 2.6 0.1214 2.8 0.0189 1.1 0.39 120.8 1.3 116.3 3.1 26.5 61.4 120.8 1.3 NA

SD007 Spot 6 175 20750 4.6 0.22 21.2931 1.4 0.1208 1.7 0.0187 1.0 0.58 119.2 1.2 115.8 1.8 46.3 32.8 119.2 1.2 NA

SD007 Spot 7 74 16128 4.0 0.25 21.0816 2.0 0.1249 2.2 0.0191 1.0 0.45 122.0 1.2 119.5 2.5 70.1 47.5 122.0 1.2 NA

SD007 Spot 8 354 181707 2.0 0.51 19.5329 2.0 0.1321 2.4 0.0187 1.3 0.54 119.5 1.6 126.0 2.9 248.6 46.9 119.5 1.6 NA

SD007 Spot 9 627 132789 3.8 0.26 20.6463 0.9 0.1283 1.2 0.0192 0.9 0.72 122.7 1.1 122.6 1.4 119.5 20.1 122.7 1.1 NA

SD007 Spot 10 329 92887 2.2 0.46 20.6450 1.1 0.1223 1.3 0.0183 0.8 0.61 117.0 0.9 117.1 1.5 119.7 24.8 117.0 0.9 NA

SD007 Spot 11 140 6776 3.9 0.26 21.2571 1.9 0.1214 2.2 0.0187 1.2 0.52 119.5 1.4 116.3 2.5 50.4 45.7 119.5 1.4 NA

SD007 Spot 12 22 116913 4.8 0.21 19.0275 4.0 0.1447 4.3 0.0200 1.5 0.34 127.5 1.8 137.2 5.5 308.7 91.4 127.5 1.8 NA

SD007 Spot 13 104 12470 5.2 0.19 21.2590 2.0 0.1226 2.2 0.0189 1.0 0.44 120.8 1.2 117.4 2.5 50.2 47.8 120.8 1.2 NA

SD007 Spot 14 171 18921 2.1 0.47 21.0586 1.4 0.1239 1.7 0.0189 1.0 0.60 120.9 1.2 118.6 1.9 72.7 32.1 120.9 1.2 NA

SD007 Spot 15 43 62349 3.1 0.33 19.8420 2.3 0.1381 2.6 0.0199 1.2 0.47 126.9 1.5 131.3 3.2 212.4 52.8 126.9 1.5 NA

SD008 Spot 36 105 44147 5.1 0.20 20.2818 2.2 0.1300 2.4 0.0191 0.9 0.38 122.2 1.1 124.1 2.8 161.4 51.2 122.2 1.1 NA

SD008 Spot 37 183 9358 3.4 0.30 17.9062 3.4 0.1441 3.5 0.0187 1.0 0.28 119.5 1.2 136.7 4.5 445.3 75.7 119.5 1.2 NA

SD008 Spot 38 40 2623 6.7 0.15 23.3494 3.8 0.1106 4.1 0.0187 1.3 0.33 119.6 1.6 106.5 4.1 NA NA 119.6 1.6 NA

SD008 Spot 39 368 197943 2.7 0.37 20.8827 1.3 0.1228 1.8 0.0186 1.2 0.67 118.8 1.4 117.6 1.9 92.6 30.8 118.8 1.4 NA

SD008 Spot 40 125 14902 6.6 0.15 20.6436 1.7 0.1275 2.0 0.0191 1.0 0.52 122.0 1.2 121.9 2.3 119.8 39.6 122.0 1.2 NA

SD008 Spot 41 182 17102 5.3 0.19 19.8035 1.5 0.1328 1.8 0.0191 1.1 0.58 121.9 1.3 126.6 2.2 216.9 34.8 121.9 1.3 NA

SD008 Spot 42 205 21379 4.5 0.22 21.2394 1.5 0.1206 1.8 0.0186 1.0 0.56 118.7 1.2 115.6 2.0 52.4 35.5 118.7 1.2 NA

SD008 Spot 43 38 2670 5.3 0.19 21.7936 3.5 0.1179 3.8 0.0186 1.3 0.35 119.1 1.6 113.2 4.0 NA NA 119.1 1.6 NA

SD008 Spot 44 65 6464 6.3 0.16 21.3582 2.1 0.1268 2.4 0.0196 1.2 0.49 125.4 1.4 121.2 2.7 39.1 49.8 125.4 1.4 NA

SD008 Spot 45 39 15262 5.7 0.17 20.4278 3.0 0.1237 3.3 0.0183 1.4 0.43 117.1 1.6 118.4 3.7 144.5 70.8 117.1 1.6 NA

SD008 Spot 46 243 22947 4.9 0.20 20.6683 1.2 0.1290 1.6 0.0193 1.0 0.64 123.5 1.3 123.2 1.9 117.1 29.3 123.5 1.3 NA

SD008 Spot 47 137 22449 7.7 0.13 20.4762 1.6 0.1257 1.9 0.0187 1.0 0.54 119.3 1.2 120.2 2.2 139.0 38.1 119.3 1.2 NA

SD008 Spot 48 74 26648 4.9 0.20 20.5333 2.1 0.1238 2.4 0.0184 1.2 0.49 117.8 1.4 118.5 2.7 132.4 49.6 117.8 1.4 NA

SD008 Spot 49 131 12576 6.2 0.16 20.8605 1.4 0.1228 1.7 0.0186 1.0 0.58 118.7 1.1 117.6 1.9 95.1 32.3 118.7 1.1 NA

SD008 Spot 50 143 6657 5.0 0.20 19.4551 3.6 0.1332 3.7 0.0188 0.9 0.23 120.1 1.0 126.9 4.4 257.8 83.1 120.1 1.0 NA

SD009 Spot 1 42 2276 3.2 0.31 22.4433 3.2 0.1265 3.5 0.0206 1.6 0.45 131.4 2.1 120.9 4.0 NA NA 131.4 2.1 NA

SD009 Spot 2 38 15265 4.1 0.24 19.0508 3.3 0.1520 3.5 0.0210 1.3 0.37 134.0 1.8 143.7 4.7 305.9 74.4 134.0 1.8 NA

SD009 Spot 3 184 27085 2.5 0.40 20.5130 1.4 0.1393 1.8 0.0207 1.2 0.66 132.3 1.6 132.4 2.3 134.8 32.8 132.3 1.6 NA

SD009 Spot 4 43 2924 3.2 0.31 21.7114 3.8 0.1373 3.9 0.0216 1.1 0.27 137.9 1.5 130.6 4.8 NA NA 137.9 1.5 NA

SD009 Spot 5 122 7664 4.4 0.23 21.4121 2.3 0.1428 2.5 0.0222 1.0 0.41 141.4 1.4 135.5 3.2 33.0 55.0 141.4 1.4 NA

SD009 Spot 6 198 14379 3.6 0.28 20.6004 1.7 0.1390 1.9 0.0208 1.0 0.50 132.6 1.3 132.2 2.4 124.8 39.6 132.6 1.3 NA

SD009 Spot 7 126 44703 2.7 0.37 19.5847 1.5 0.1552 1.9 0.0221 1.2 0.63 140.6 1.6 146.5 2.6 242.5 33.8 140.6 1.6 NA

SD009 Spot 8 33 6213 4.9 0.21 21.7691 4.0 0.1355 4.2 0.0214 1.2 0.29 136.6 1.6 129.1 5.1 NA NA 136.6 1.6 NA

SD009 Spot 9 188 14232 3.5 0.28 20.6334 2.0 0.1219 2.2 0.0182 0.9 0.41 116.5 1.1 116.8 2.5 121.0 47.8 116.5 1.1 NA

SD009 Spot 10 248 13129 2.5 0.40 21.0302 1.1 0.1374 1.5 0.0210 1.1 0.70 133.8 1.4 130.8 1.9 75.9 26.2 133.8 1.4 NA

SD009 Spot 11 58 14019 5.0 0.20 20.4878 2.6 0.1435 2.9 0.0213 1.1 0.39 136.0 1.5 136.1 3.7 137.7 62.1 136.0 1.5 NA

SD009 Spot 12 77 58802 3.8 0.26 19.9514 1.9 0.1509 2.2 0.0218 1.1 0.50 139.3 1.5 142.7 2.9 199.7 43.7 139.3 1.5 NA

SD009 Spot 13 279 30541 4.1 0.24 20.4146 1.2 0.1437 1.8 0.0213 1.3 0.73 135.7 1.8 136.3 2.3 146.1 28.7 135.7 1.8 NA

SD009 Spot 14 54 4625 4.0 0.25 21.6583 3.1 0.1340 3.3 0.0211 1.2 0.37 134.3 1.6 127.7 4.0 5.5 74.5 134.3 1.6 NA

SD009 Spot 15 86 5282 3.0 0.34 20.4108 2.6 0.1390 2.9 0.0206 1.2 0.43 131.3 1.6 132.1 3.5 146.5 60.6 131.3 1.6 NA

70

Figure A-10 Average U-Pb ages for sample SD004

Figure A-11 Average U-Pb ages for sample SD006

71

Figure A-12 Average U-Pb ages from sample SD007


72


73

Table A-2: In Situ Lu-Hf isotopic data of zircons from this study

Sample (176

Yb + 176

Lu) / 176

Hf (%) Volts Hf176

Hf/177

Hf ± (1s)176

Lu/177

Hf176

Hf/177

Hf (T) E-Hf (0) E-Hf (0) ± (1s) E-Hf (T) Age (Ma)

MALONE-CASARES SD004 SPOT1 23.7 5.9 0.282998 0.000021 0.001554 0.282994 7.5 0.7 10.5 139.1








MALONE-CASARES SD004 SPOT9 9.8 5.2 0.283346 0.000022 0.000759 0.283344 19.8 0.8 22.7 131 *







MALONE-CASARES SD006SPOT36 7.7 7.3 0.283016 0.000017 0.000609 0.283015 8.2 0.6 10.9 125.7












MALONE-CASARES SD006SPOT49 6.3 6.2 0.283233 0.000020 0.000597 0.283231 15.8 0.7 18.5 122 *








MALONE-CASARES SD007 SPOT7 6.1 8.3 0.283006 0.000015 0.000527 0.283005 7.8 0.5 10.5 122



MALONE-CASARES SD007 SPOT10 7.9 8.8 0.282985 0.000017 0.000573 0.282984 7.1 0.6 9.6 117






MALONE-CASARES SD008 SPOT 36 11.5 5.4 0.28298 0.000019 0.000846 0.282979 6.9 0.7 9.6 122.2




MALONE-CASARES SD008 SPOT 40 10.2 5.9 0.283019 0.000016 0.000693 0.283017 8.3 0.6 10.9 122



















MALONE-CASARES SD009 SPOT 10 23.5 5.2 0.283557 0.000021 0.001544 0.283553 27.3 0.7 30.1 134 *






* Burned Through the grain, plots above the DM

74

Table A-3: Average εHf(t) and errors for the Seven Devils samples.

Table A-4: Loss on Ignition (LOI)

Average εHf(t) error 2se

SD004 11.7 1.50

SD006 11.0 1.40

SD007 10.8 0.85

SD008 10.4 1.04

SD009 10.1 0.62

Sample # Crucible Crucible+Sample Sample S+C 65-70 degrees 65-70 degrees 1st stage S+C 110-120 degrees 110-120 degrees

SD001 11.2704 21.2474 9.977 21.2234 9.953 0.024 21.2131 9.9427

SD002 11.7811 21.0808 9.2997 21.0561 9.275 0.0247 21.0476 9.2665

SD003 10.8525 21.1721 10.3196 21.1472 10.2947 0.0249 21.1345 10.282

SD004 11.4335 21.1055 9.672 21.0869 9.6534 0.0186 21.0793 9.6458

SD005 11.6708 21.0846 9.4138 21.0601 9.3893 0.0245 21.0493 9.3785

SD006 11.4467 21.2702 9.8235 21.2508 9.8041 0.0194 21.24 9.7933

SD007 11.4476 21.1087 9.6611 21.0839 9.6363 0.0248 21.0732 9.6256

SD008 11.0804 21.1279 10.0475 21.1081 10.0277 0.0198 21.099 10.0186

SD009 11.2517 21.1233 9.8716 21.1002 9.8485 0.0231 21.0889 9.8372

2nd stage S+C 1000 degrees 1000 degrees 3rd stage %Change1StStage %Change2nDStage %Change3RDStage

SD001 0.0343 20.9795 9.7091 0.2679 0.2406 0.3438 2.6852

SD002 0.0332 20.6354 8.8543 0.4454 0.2656 0.3570 4.7894

SD003 0.0376 20.9105 10.058 0.2616 0.2413 0.3644 2.5350

SD004 0.0262 20.9387 9.5052 0.1668 0.1923 0.2709 1.7246

SD005 0.0353 20.9865 9.3157 0.0981 0.2603 0.3750 1.0421

SD006 0.0302 21.1526 9.7059 0.1176 0.1975 0.3074 1.1971

SD007 0.0355 20.9905 9.5429 0.1182 0.2567 0.3675 1.2235

SD008 0.0289 20.9401 9.8597 0.1878 0.1971 0.2876 1.8691

SD009 0.0344 20.97 9.7183 0.1533 0.2340 0.3485 1.5529

The averages show that the

samples are very clustered

around 10.1 to 11.7 with small

errors.

75

Table A-5: Whole Rock Geochemistry for the Seven Devils terrane determined by XRF

Sample # Na2O MgO Al2O3 SiO2 P2O5 K2O CaO Sc TiO2 V Cr MnO Fe2O3

SD001 3.228 59.536 0 26.389 0.248 0.241 0.317 0.002 1.293 291.779 109.474 0.142 11.715

SD002 1.755 8.382 15.624 36.803 0.248 0.328 7.985 0.002 0.414 68.714 35.538 0.098 4.268

SD003 1.482 5.778 14.794 37.028 0.248 0.241 9.073 0.002 1.102 384.707 70.751 0.213 12.513

SD004 1.991 5.306 11.017 39.471 0.248 0.487 7.93 0.002 0.486 70.958 51.424 0.093 4.551

SD005 1.26 4.388 12.278 40.342 0.248 0.612 7.387 0.002 0.444 87.977 69.914 0.106 4.351

SD006 1.511 1.87 10.095 43.914 0.248 1.352 4.755 0.002 0.545 114.015 49.212 0.124 5.458

SD007 2.001 0.937 12.091 50.658 0.248 2.017 4.095 0.002 0.352 29.732 10.117 0.051 2.561

SD008 1.168 0.574 10.092 54.178 0.248 4.622 1.658 0.002 0.313 46.49 18.943 0.076 2.801

SD009 2.532 0.574 11.11 51.644 0.248 2.381 2.268 0.002 0.346 56.264 43.005 0.093 3.545

Sample # Co Ni Cu Zn Ga Rb Sr Y Zr Nb Ba Pb

SD001 33.35 51.099 13.383 80.555 11.775 12.166 251.457 20.007 60.643 0 298.265 7.47

SD002 9.913 29.046 15.386 63.488 18.968 39.94 200.541 12.689 145.614 1.858 465.886 0.315

SD003 29.024 27.814 70.515 56.226 18.229 6.075 201.287 23.682 43.372 0 298.265 0

SD004 12.373 35.413 30.778 67.497 20.722 11.483 433.645 12.186 132.635 4.774 298.265 8.551

SD005 14.469 33.454 45.999 67.595 23.462 23.074 651.796 7.085 99.203 1.54 401.999 0

SD006 16.747 23.871 150.945 60.751 17.772 12.763 579.383 8.422 83.169 1.053 298.265 0

SD007 11.078 11.175 23.839 70.176 25.888 20.318 759.482 1.934 122.959 2.533 413.127 0

SD008 10.033 13.815 0.127 71.001 28.134 17.759 709.59 8.03 111.675 0 626.044 0

SD009 7.69 32.035 51.764 56.947 19.566 24.018 421.865 1.094 126.151 0.863 342.869 3.263

76

Figure A-15: Intrusive Rock Diagram Using Immobile Trace Elements


using Nb vs. Y.

The discrimination

diagram modified from

Winchester and Floid

(1977) shows that the

Seven Devils samples all

plot in the diorite to

syenitic diorite range.

SD001, SD003, and

SD008 did not plot due

to the Nb being too low

for the XRF to detect.

The discrimination

diagram modified from

Pierce et al. (1984)

shows that the Seven

Devils samples have a

Volcanic arc and syn

collision granites

signature. Samples

SD001, SD003, and

SD008 did not plot due

to Nb being too low to

detect.

77


using Rb vs. Nb+Y.

The discrimination

diagram modified

from Pierce et al.

(1984) shows that the

Seven Devils samples

have a Volcanic arc

signature.

zircon geochemistry and geochronology of the seven devils …

Documents