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Hydrothermal Alteration in the Propylitic Suite at Butte, Montana

By: Kyle Haggart, University of Oregon

May 2014

Introduction

The Butte porphyry copper deposit formed 65 to 62 million years ago when the

Butte Quartz Monzonite was fractured and altered by magmatic hydrothermal fluids

(Mercer and Reed, 2013). Porphyry copper deposits are most commonly found at

subductive plate boundaries, which provides the needed magma and fluids to form the

deposits (Sillitoe 2010). Porphyry deposits form when a magma body at depth begins to

crystallize, resulting in high pressures in the cupola of the magma body. Once the fluids

become over pressured they break the overlying rock,

creating porphyry dikes with a stock work of fractures

(Mercer and Reed, 2013) (figure 1). The released fluids

from the magma body flow through the network of

fractures and as they travel upwards and outwards they

interact with the surrounding rock producing hydrothermal

alteration of the fractured wall rocks (Mercer and Reed

2013). As the fluids cool they precipitate large quantities

of sulfides and quartz and lesser amounts of copper,

molybdenite, and potentially trace amounts of other metals

such as silver. (Seedorff et al. 2005) Porphyry copper

deposits all around the world provide an important source

of resources needed to sustain our lives.

The alteration types vary depending on how far the

alteration is from the magma source, the acidity of the

fluid, as well as the size of the vein (Rusk et al. 2008). The

Butte porphyry copper deposit is separated into zones

based on the alteration types; there is the potassic zone,

the sericitic zone, and the propylitic zone (figure 2)

Figure 1: Shows the evolution of a magma body at depth which produces porphery copper deposits. First the cupola begins to crystallize (a), which results in increased pressure causing the magma to eventually break though and intrude into the wall rock (b). The fractures then seal (c) and the cupula begins to repressurizing once until once again it becomes over pressured and hydrofracturing occurs releasing the fluids that cause metasoatism of the wall rock (d). ( Mercer and Reed, 2013)

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(Sillitoe 2010). Porphyry copper deposits all around the world display similar alteration

patterns to the ones found at the Butte deposit, but Butte is unique because it has two

domes with the sericitic alteration zone in between them (Rusk et al., 2008). The more

highly altered zones are founded towards the center of the deposit and the least altered,

propylitic zone, is found in the periphery.

Since the propylitic zone is at the edge of the deposit it experiences the smallest

degree of alteration, leaving the granitic texture intact (Sillitoe, 2010). Small degrees of

alteration do occur, such as feldspar and biotite being altered to chlorite, epidote, albite

and carbonates. Possible accessory minerals in this zone include actinolite, hematite, and

magnetite and the sulfides present are predominantly pyrite, with some sphalerite and

Figure 2: A schematic showing the basic layout of a porphyry copper deposit. The highly altered zones are in the center, above the magma body with the propylitic zone around the other alteration zones. The zones are distinguished based on the alteration types that occur. The deposit at Butte is unique because it has two domes with the sericitic alteration in between them. (Sillitoe, 2010)

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galena (Sillitoe, 2010). The propylitic zone has the smallest concentrations of metal

compared to the other zones, but it is commonly volumetrically large.

The main alterations present at the Butte Porphyry Copper deposit are described

by the vein types they are associated with, which are: early dark micaceous (EDM), pale

green sericitic (PGS), barren quartz/quartz-molybdenite (BQ/QMB), gray sericitic (GS),

and main stage (MS) veins. Studies of fluid inclusions from the veins at Butte provide an

estimated temperature and pressure of formation (Rusk et al, 2008). The main stage veins

were found to have formed from fluids between 230°C and 400°C and at pressures

between 40 and 70 MPa (Rusk et al. 2008). The deepest alteration (EDM) formed at

temperatures between 575°C and 650ºC with pressures ranging from 200 to 250 MPa

(Rusk et al 2008). Considering that the propylitic alteration occurs relatively far from the

heat source it can be guessed that the temperature range should be closer to the main

stage vein temperatures. A study on the alteration of granitic biotite to chlorite by

Eggleton and Banfield shows that the alteration of two biotite sheets to one chlorite sheet

though metasomatism occurs at roughly 330°- 340°C (1985). In another study on

hydrothermal alteration mineralogy done by Lagat, the alteration from biotite to chlorite

occurred in a temperature range of 220° to 340° C (2009). From these studies we can

conclude an expected temperature range of roughly 230° C to 340°C for the propylitic

zone.

The propylitic zone has small veinlets of quartz sulfides throughout the area,

resulting in smaller alteration envelopes than the other zones. The veinlets observed

consist of mostly quartz with some pyrite, chalcopyrite, and sphalerite. The alteration

envelopes surrounding the veins consist of clusters of chlorite and epidote making it

distinctly different than any other alteration envelope (Sillitoe 2010). The main

metasomatic reaction in the propylitic zone is biotite being altered to chlorite and sphene.

The alteration does not consistently replace all of the original biotite, but commonly

leaves behind remnant material. Plagioclase and potassium feldspars are also commonly

altered to sericite and epidote and are usually found in close proximity to altered biotite.

In general, most of the economically recoverable metals are found in the other

zones (Sillitoe 2010) and as a result the propylitic zone has received little study. The zone

of the propylitic suite is volumetrically large thus, even though the concentrations of

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metals are small, it could still hold significant amounts of resources due to the large

volume of the alteration zone (Reed, Personal Communication).

Chlorite- Biotite Alteration

Chlorite is a sheet silicate with the layered structure of mica. The chemical

formula for chlorite is (𝑀𝑔, 𝐴𝑙, 𝐹𝑒)12[(𝑆𝑖, 𝐴𝑙)8𝑂20](𝑂𝐻)16 with Al occurring in both the

tetrahedral site as well as the octahedral site. Chlorite has a tetrahedral-octahedral-

tetrahedral (T-O-T) structure similar to talc, but has (Mg,Al,Fe) filling the octahedral

layer (Deer, 1992). Chlorite refers to a group of four end members, the most important

for this study being clinochlore (magnesium) and chamosite (iron).

Biotite is part of the mica group of minerals and is a sheet silicate with the

formula 𝐾(𝑀𝑔, 𝐹𝑒2+)3𝐴𝑙𝑆𝑖3𝑂10(𝑂𝐻, 𝐹)2. The most significant end members are annite

(iron) and phlogopite (magnesium). As part of the mica family, biotite has a T-O-T

structure with potassium filling the octahedral layer (Deer, 1992).

Since both chlorite and biotite have similar structures, the replacement of biotite

by chlorite can happen with relative ease. In the replacement of biotite by chlorite the

element filling the octahedral layer of the structure is freed. If the magnesium end

members, phlogopite and clinochlore, are assumed for biotite and chlorite respectively

then the chemical reaction is

2𝐾𝑀𝑔3𝐴𝑙𝑆𝑖3𝑂10(𝑂𝐻)2 + 4𝐻+ = 𝑀𝑔5𝐴𝑙2𝑆𝑖3𝑂10(𝑂𝐻)8 + 2𝐾+ +𝑀𝑔2+ + 3𝑆𝑖𝑂2

(Parry and Downey 1982). In the propylitic suite the chemical composition of biotite and

chlorite is more complex than this, being a mixture of magnesium and iron for the

chlorite and biotite having minor titanium substituted for the silicon (Deer, 1992). As a

result when this reaction takes the ions that are possibly freed to form new minerals are

magnesium, iron, potassium and trace amounts of titanium.

Methods

A limited number of samples were available from the propylitic zone of Butte,

Montana. Eight hand samples were observed ranging from 383 feet of depth to 760 feet

of depth and one unaltered Butte quartz Monzonite rock was observed. Six of the samples

contained veins cutting though them, ranging from ¼ to 4 mm wide. Each rock was

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closely examined with a hand lens noting texture, vein relationships, alterations, and

possible compositions. Sample names indicate the depth at which the sample was taken

from within the propylitic zone, e.g. sample 620 is from 620 feet below the surface. All

the samples were taken from drill hole 10969 except sample 760, which is from 11166.

The fresh quartz Monzonite was sampled from an outcrop outside of the alteration zone

of the porphyry copper deposit at Butte, Montana.

Light Microscopy

A transmitted light microscope was used to examine seven thin sections. Four of

the seven thin sections had been previously prepared and stained resulting in the

potassium feldspars appearing yellow making them easily distinguishable from quartz.

The previously prepared thin sections are sampled from 383, 500, 534, and 620 feet of

depth. Two more thin sections were created for samples at 383 feet and 534 feet of depth

and one additional one for the fresh Butte quartz monzonite. Objective lenses of 4 times

and 10 times were used to examine the thin sections, resulting in 40 times to 100 times

magnification. Samples were observed under plane polarized light and cross polarized

light. Birefringence, interference colors, and interference figures were used to help

identify minerals present in each section.

Scanning Electron Microscopy

The SEM analysis was done using an FEI Quanta 200 FEG scanning electron

microscope equipped with a Thermo SDD energy dispersive spectrometer detector

located at the University of Oregon. The three polished thin sections prepared from

samples 534, 620, and Bu were carbon coated and analyzed. The scanning electron

microscope was set to 20kV with a working distance of 10mm. A spot size of 4 microns

was used for single point analysis, then was changed to 6 microns for elemental mapping.

The SEM was used to gather qualitative data for twenty-two different areas of interest

and three elemental maps were collected. The SEM was used to identify minerals and the

unique textures displayed by the alteration in this zone.

Electron Microprobe

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Two separate runs were done using an electron microprobe. The first run was

completed on sample 620, which was prepared as a 1.5 cm diameter cylinder by 1.5 cm

thick section of rock. The sample was carbon coated (15-20 nm) and then analyzed using

the Cameca SX-50 electron microprobe located at the CAMCOR facility at the

University of Oregon. The beam energy was set at 15 keV and the beam current was

30nA. The diameter of the beam was 5 microns and the elements analyzed were: Fe, Ti,

Mn, P, K, Ca, S, Cl, Si, Mg, Al, and Na. Three different crystals were used (LIF, PET,

TAP) to analyze the elements. Iron, titanium and manganese were put on the LIF crystal,

phosphorus, potassium, calcium, sulfur, chloride, and silicon were put on PET crystals,

and magnesium, aluminum, and sodium were put on TAP crystals. All the elements used

a count time of 10 seconds. This sample is referred to in following figures as Run 1

followed by the mineral being discussed (table 6).

The second run was completed using the Cameca SX-100 electron microprobe

located in the CAMCOR facility at the University of Oregon. This run used a beam

current of 30 nA and a beam energy of 15 keV. The beam size was set at 10 microns and

the elements analyzed were Fe, Ti, Si, Ca, Mn, K, Al, Mg, Na, and P. A LIF crystal was

used on Fe and Ti. A LPET crystal was used for Si, Ca, Mn, and K, and a TAP crystal

was used for Al, Mg, Na, and P. The counting times were optimized to have 40 second

counts on K, Mn, and P, 50 second count times on Ti, 60 second count times on Fe and

Si, and 75 seconds on Ca, Al, Mg, and Na. This run was used to analyze the same three

samples that were previously analyzed using the SEM, samples 534, 383, and Bu. The

samples were polished thin sections that were carbon coated to ensure conductivity. Data

from this run is referred to as Un (unknown) followed by a number which corresponds to

a sample found in tables 1-5.

Hand Samples

All of the samples from the propylitic suite still display a granitic texture with

slight alterations to the mineral assemblages. In all of the rocks there are abundant green

minerals that appear to be chlorite and epidote and black minerals which are biotite. The

majority of the crystals present in the samples are unaltered feldspars and quartz from the

original granite.

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Most of the samples have veinlets cross cutting though the samples which

consisted mainly of quartz and some sulfides. In many of the veins the black mineral was

identified as magnetite based on hand samples, but SEM analyzes the most abundant

sulfide is sphalerite, which can appear black in hand samples. Sample 500 displays a

reddish hue along the vein, indicating an oxidation of possibly magnetite, which would

mean magnetite and sphalerite are both present in the veins. The veins range anywhere

from ¼ mm to 4 mm think and appear scattered throughout all samples except for sample

338. Immediately near the veins more extreme alteration is present in the form of

increased epidote and chlorite, which could be seen with a 10x hand lens.

Figure 3: From left to right: Sample Bu, 383, 620, and 534. These four samples were analyzed on the SEM as well as the EMPA. Sample 620 has a 3mm vein of quartz and pyrite. Sample 534 has a .25mm vein of a black mineral most likely magnetite. The granitic texture of the altered rocks (383, 620, and 534) resembles that of the unaltered Butte quartz Monzonite (Bu). Green and

black minerals can be seen throughout the samples which are identified as biotite, chlorite and epidote.

4.5 cm

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Figure 4: From top to bottom: Sample 500, 555, 338, and 760. All the samples display the original Butte quartz monzonite texture. Sample 760 has a 4mm vein of black mineral which could be magnetite, but SEM work on other veins shows it could be sphalerite. Sample 555 has a 0.5mm vein consisting of quartz and pyrite through it. Sample 383 appears more highly altered to epidote and chlorite than the rest of the samples, even though no vein is present. Sample 500 has some red coloration along the 0.5mm vein

indicating an oxidation affect associated with magnetite present in the vein.

4 cm

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Petrography

All of the thin sections contain similar alterations, but some samples contain more

advanced alteration than others due to the presence of veinlets. Samples 534 and 383

have visible veinlets in the thin sections resulting in increased alteration immediately next

to the vein. Figure 5 shows part of the vein that consists mostly of quartz with some

small concentrations of sulfides bordering the vein. Within the vein primary chlorite is

present and can be observed within 0.2 mm of the quartz vein. The envelope minerals

within 1 mm from the vein have been highly altered to chlorite, epidote, and sericite.

Chlorite that is 1 mm away from the vein in the bottom right of figure 5 displays a more

platey texture than the irregular shape of the primary chlorite immediately near the quartz

vein.

As biotite is altered to chlorite a mixture of chlorite (65%), epidote (10%), sphene

(10%) and void space (15%) is created (Eggleton and Banfield, 1984). The alteration of

biotite to chlorite, sphene, and epidote is most clearly seen immediately near veins (figure

5), but can be found in the propylitic zone as a whole. In all the samples, epidote and

sericized plagioclase occurs within close proximity to or touching chlorite that replaces

biotite (figure 8).

Figure 5: Sample 534 at 40 times magnification in plane polarized light. The sample displays a 1/8mm vein cutting across the sample. The vein consists of mainly quartz with sulfides and chlorite immediately adjacent to it. The alteration envelope (about 1mm from vein) in the rest of the view displays chlorite, epidote, and sericite that has replaced feldspars and biotite.

Figure 6: Sample 534 at 40 times magnification in cross polarized light. The vein (1/8 mm think) is mostly quartz that has gone to extinction and is surrounded by highly altered plagioclase. The light blue plagioclase crystal has been replaced mainly by sericite. Roughly 0.3 mm from the vein in the upper right corner is a cluster of bright colored crystals, which are epidote.

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Throughout all the samples, the main minerals of alteration are biotite and

feldspars, mainly plagioclase. In figure 7 it can be seen that around the vein the majority

of the alteration is occurring in one mineral. The mineral is identified as a feldspar from

the observed birefringence, extinction behaviors, as well as the albite twinning (figure 7).

This type of alteration is found in varying degrees throughout all the samples. Feldspars

within close proximity to veins observed display high degrees of seritization. In the

samples without veins or further than 0.5 mm from a vein, sericitic alteration is abundant,

but usually does not result in complete replacement of the original feldspar crystal.

Alteration of plagioclase is necessary for many of the alterations to occur because of the

limited supply of calcium throughout the rock.

Plagioclase is an important mineral of alteration because in most cases it supplies

the calcium needed to form sphene and epidote. All the alteration chlorite forms with

sphene scattered within the chlorite grain and epidote close to the crystal. As biotite is

replaced by chlorite many elements are released that are needed to form sphene and

epidote, but calcium must come from another source. Plagioclase is abundant in the Butte

quartz monzonite and as it is altered to muscovite calcium is released. Close to veins it

appears that more alteration can take place because of a supply of calcium from the

hydrothermal fluid.

Figure 7: Sample 620 at 40 times magnification under cross polarized light. The centered plagioclase crystal displays albite twinning and is partially

replaced by sericite.

Figure 8: Sample 383 at 40 times magnification under cross polarized light. An alteration chlorite crystal is centered in the image with opaque sphene scattered within the grain. Epidote clusters of many small epidote crystals are shown in the upper left and right corner, which have replaced plagioclase. The bottom right crystal is a plagioclase crystal,

which appears to also have epidote throughout it.

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The main alteration of interest is the replacement of biotite by chlorite. Biotite is a

common mineral in the original Butte quartz Monzonite and it appears as an elongated

sheet silicate as pictured in figure 9. As the alteration occurs, the shape of the biotite

remains and is replaced pseudomorphically. The main pseudomorphic mineral is chlorite,

which also appears to host an opaque mineral identified by the SEM as sphene. Figure

10 shows a biotite grain that has been altered almost completely to chlorite with sphene

scattered throughout the chlorite crystal.

The sphene is a confounding discovery because under the transmitted light

microscope it appears in an uncommon opaque form, but SEM and microprobe analysis

identify it as sphene. Transparent sphene is questionably found in a few chlorite grains

throughout all the samples (figure 13), but could not be distinguished in the SEM and

EMPA analyzes to confirm the composition. In many cases the sphene takes on the shape

of the original biotite, causing it to appear elongated. The opaque mineral is found in

every sample of alteration chlorite from the propylitic zone and is commonly in the

pseudomorphic form. It appears as if the sphene formed at the same time as the chlorite

because it takes the shape of the original biotite and it is not found outside of the chlorite

grain. The sphene most likely forms as a result of the release of titanium that was held in

the biotite structure.

Figure 10: Sample 383 at 40 times magnification under plane polarized light. In the center of the image is a highly altered biotite. The remnant biotite is replaced by chlorite and an opaque mineral which SEM and EMPA identify as sphene. The bottom mineral is quartz and to the left of the image is clusters of epidote.

Figure 9: Sample 534 at 40 times magnification under plane polarized light. The elongated sheet silicate in the middle of the picture is unaltered biotite from the propylitic zone. The mineral to the top right of the picture is unidentified, but is possibly sphene. To the bottom right of the image is a cluster of epidote.

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Non-replacement chlorite (primary chlorite) is found only in the veins of samples

534 and 383. The primary chlorite appears sporadically throughout the vein and occurs in

small clusters. The primary chlorite has a much more irregular shape than the alteration

chlorite as well as having an unusual banding pattern when looked at in cross polarized

light (figure 13).

Chlorite easily replaces biotite because both minerals are sheet silicates, which

allows for minimal structure change, and both minerals contain Mg, Fe, Al, and Si. All

the samples displayed a similar behavior of alteration in which if any biotite remained it

was almost in the exact middle of the chlorite, meaning that the alteration occurred from

the outside inward at a constant rate around the whole grain. As the replacement occurs,

titanium and potassium are freed from biotite and the Ti becomes the building block for

sphene, which forms at the same time as the chlorite. The sphene in figure 10 appears to

be elongated, taking the shape of the original biotite. Most of the pseudomorphic chlorite

appears throughout the sample volume with remnant biotite present and sphene, which

are commonly present near epidote and sericite.

Figure 12: Primary chlorite in a vein from sample 534 at 100 times magnification seen in cross polarized light. The chlorite displays a unique banding pattern, which alteration chlorite lacks. The white mineral is quartz and the bottom left corner has a seritized plagioclase crystal. Scattered epidote crystals display bright interference colors.

Figure 11: Sample 534 at 40 times magnification under plane polarized light. Centered in the image is a vein filled with almost entirely chlorite and some quartz. The primary chlorite displays an irregular shape. Surrounding the vein is highly altered plagioclase. Surrounding the vein is epidote and

highly altered plagioclase.

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Some of the alteration chlorite displays a mysterious blue interference color

around some of the opaque minerals and remnant biotite (figure 13). This observation

suggests that the chlorite could be chemically different due to interactions with the

titanium from the sphene and biotite causing it to have a blue birefringence.

Figure 13: Sample 500 at 100 times magnification under cross polarized light. SEM and data identifies the opaque mineral as sphene. The blue interference colors appears to form around the high iron sphene crystal inside the chlorite grain. The image also

shows a brown to white mineral, which is possibly low iron sphene.

Figure 14: Sample 620 at 40 times magnification under cross polarized light. Chlorite with opaque sphene is pictured in the bottom left with epidote forming clusters to the right of the chlorite grain. Epidote is found as small crystals grouped into larger clusters, which appear to be replacing the plagioclase.

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Epidote is another very common alteration mineral in the propylitic suite. It

appears to replace feldspars, mainly plagioclase due to the supply of calcium needed to

form these crystals. The epidote found throughout these samples is always in close

proximity to chlorite due to the iron and magnesium released from the chlorite alteration.

The epidote forms relatively small crystals and is always found in large clusters (figure

14

Scanning Electron Microscope Imaging

To further analyze the samples from the propylitic suite, a scanning electron

microscope was used to get a general makeup of the elements present in the selected

samples. The SEM allowed for three samples to be mapped using elemental mapping and

backscatter electron detection. The two altered rocks analyses showed similar

characteristics in texture and composition despite the rocks being 150 feet of depth apart.

Sample 383 has a quartz sulfide vein cutting through the sample that also contains

primary chlorite (figure 15 & 16). Primary chlorite is distinctly different from alteration

chlorite because it exhibits a distinct pattern that occurs in all of the primary chlorite

found in the vein. The interlaced light and dark band pattern shown on the SEM (figure

15 & 16) implies that the lighter chlorite bands have a heavier mean atomic number and

the darker bands have a lighter mean atomic number. An analysis on the same grain as in

Figure 16: Sample 383 displaying a primary chlorite grain surrounded by sphalerite in a vein. The chlorite displays the same banding pattern as other primary chlorite found in veins. SEM work also showed that the primary sulfide in the veins was sphalerite. (white mineral).

Figure 15: Sample 383 highly magnified on a chlorite grain in a cross cutting vein. The chlorite grain displays a banding pattern of two different bands. The lighter band has a higher mean atomic number than the darker bands. The primary chlorite grain is in a quartz vein with a sulfide present (white mineral).

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figure 15 on the EMPA shows that the lighter bands consist of more iron and less

magnesium than the darker bands.

The alteration chlorite is distinctly different from the primary chlorite in quartz

veinlets. Alteration chlorite commonly occurs as a pseudomorph of biotite and in many

observed samples contains remnant biotite. The alteration also results in the formation of

another mineral throughout the chlorite crystal. The SEM confirmed that the mineral

present in the chlorite was CaTiSiO5, or sphene. Figure 17 shows the chlorite, and

surprisingly, the sphene holding the original biotite shape. Sphene commonly occurs in a

more blocky shape, but since this alteration replaces a sheet silicate, the sphene forms as

Figure 19: Sample 383 shows a chlorite grain surrounded by blocky sphene, which is surrounded by chlorite. This image is the only found instance in which sphene appeared in its more common blocky form and at is found at a larger scale than most

other sphene.

Figure 18: SEM image of sample 383. Chlorite is displayed having replaced all but the center biotite grain. Sphene is scattered throughout the chlorite as an elongated mineral. Unaltered quartz and potassium feldspar are in the upper and lower left corner. Slightly altered k-feldspar is visible in the upper right corner.

Figure 17: Sample 534 shows a chlorite crystal that has fully replaced the original biotite. As a result the chlorite and the sphene have taken the shape of the original biotite grain.

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a platy elongated mineral. In one case sphene is found to be forming around a chlorite

grain that is located inside another chlorite grain (figure 19). In this example the sphene

appears to be taking a more blocky

shape, coming to a point on one side of

the crystal.

Figure 21 is an element map

view of figure 18 in which chlorite is

replacing a biotite grain and creating

sphene in the process. The grain is

surrounded by potassium feldspars and

quartz. The elemental map (figure 21)

clearly shows titanium being present in

the biotite grain as well as concentrated

amounts in the scattered sphene grains.

In figure 21 the elemental map view

makes the distinctly different minerals obvious. Potassium feldspar (blue) remains

unaltered in the corners of

the figure and the

magnesium and iron became

more concentrated in the

chlorite grains. The

pseudomorphic behavior of

sphene is shown as the

streaky teal color (figure

20).

The calcium needed

to form sphene could come

from freed calcium ions as

plagioclase undergoes

alteration. As plagioclase

decalcifies through sericitic alteration, the calcium diffuses from the point of alteration to

Figure 21: A elemental map of figure 15 (sample 383). Each element of interested are given the following color code: Green=Calcium, Teal=Titanium, yellow=magnesium and iron, and blue=potassium. The chlorite is shown consisting of large quantities of iron and magnesium and the biotite can be seen having titanium. The sphene has large quantities of both calcium and titanium. The upper right and bottom left corners consist of potassium feldspars.

Figure 20: An elemental map from sample 383, same view as figure 15. The teal color displays only the titanium found in the sample, which can be seen to be concentrated in the sphene crystals as well as in the remnant biotite.

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a nearby fracture. Along the way the calcium interacts with the biotite-chlorite alteration.

The elemental maps provide evidence that the titanium needed for the formation of

sphene orginates from the biotite crystals. As chlorite replaces biotite, the titanium

originally in the biotite structure is freed and interacts with nearby calcium to form

sphene. The sphene most likely formed at the same time as the chlorite due to sphene not

being present outside of the chlorite grain as well the sphene appearing elongated.

Another source of calcium could be from the hydrothermal fluids. The fluids that

create the Butte porphyry copper deposit are of one composition (Reed et al., 2013). As a

result the same fluids interact with rocks along the way to the distal propylitic zone

causing the diffusion of ions into and out of the fluid. In all the other zones plagioclase is

one of the first minerals to be altered (Sillitoe 2010), freeing calcium ions and allowing

them to diffuse into the fluid. Once the fluid reaches the propylitic zone the calcium

reacts with the magnesium, iron, and titanium that is being freed from the biotite to create

epidote, sphene, sulfides, and in some cases carbonates. However, titanium should not be

present in the hydrothermal fluids because of the low temperatures the fluids are at once

they get to the propylitic zone and because of the insolubility of titanium. As a result the

heavy metals found in epidote and sphene must come from the alteration of biotite and

other nearby minerals.

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Other minerals found throughout the samples are sphalerite, chalcopyrite, pyrite,

and sphene. In the vein, sphalerite is the main sulfide with chalcopyrite being the second

most abundant and very little pyrite is present. Metal bearing sulfides are mainly in the

veins because the hydrothermal fluids that flow in the fractures contain a supply of zinc

and copper (Sillitoe, 2010). Throughout the rest of the samples the main sulfide present is

pyrite. Despite the previous observation that galena was common in the propylitic zone

(Mercer and Reed, 2013), no galena was found in any of the samples.

In the propylitic suite small veinlets are widely abundant similar to the magnified

vein shown in figure 22. If these veins contain sphalerite and chalcopyrite in similar

quantities such as found in sample 383, then this zone could hold a huge reserve of zinc

and copper.

Figure 22: A vein found in sample 383. The lightest shade of gray (white) is identified as sphalerite. The surrounding minerals were not identified, but based on other SEM analysis’s the vein is mostly quartz with some feldspars and sparse chlorite.

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Micro Probe Analysis

Two runs were completed using the EPMA in the CAMCOR Lokey laboratory at

the University of Oregon. Both runs were optimized for the analyses of chlorite, biotite,

epidote, feldspars, and sulfides in the samples. The alteration of biotite to chlorite was the

focus of the two runs in hope that it could be used as a geothermometer to tell us what the

temperature was at the time of chlorite precipitation. The analysis showed that chlorite

has a large range of iron to magnesium concentrations (graph 1). The samples seemed to

show a pattern of more iron and less magnesium as depth increases. Primary chlorite

(samples Un 12,13, and 14) is shown to have a higher magnesium content than alteration

chlorite, but still has a large amount of variability in the compositions (Mg3.995-5.572Fe4.127-

4.723Mn0.18-0.248Al2.908-2.212)[(Si5961-0.5Al2.039-2.5)O20] (table 1). The primary chlorite also

exhibits a banding pattern in which one band has a higher mean atomic number than the

other band. Analyses of the chlorite in figure 12 shows that the two zones range by

almost 2 weight percent in iron content.

Graph 1: Iron verses magnesium is shown on the above graph. Sample Un 12, 13, and 14 are primary chlorite found in the vein of sample 383. Sample Un 13 corresponds with the chlorite pictured in figure 9. All other points are alteration chlorite and are average of all the points analyzed on the EMPA.

Haggart 20

Anaylsis of feldspars showed a large range of compositions, from plagioclase to

alkali feldspars. The fresh rock had less pure alkali feldspars compared to the altered

rocks. Sample 383 contains an altered potassium feldspar grain with the formula

(K0.962Na0.049)(Al1.048Si2.96O8) and the unaltered rock had the composition of

(K0.709Na0.301Ca0.013)(Al1.062Si2.942O8). The altered rock has a 0.253 increase in the

potassium cation concentration. In the fresh Butte granite the plagioclase was found to be

(Na0.611-0.542Ca0.459-0.414K0.02-0.013)(Al1.469Si2.53O8). In the altered rock plagioclase is

almost always altered to some degree, but one analysis was done on sample 383 which

fell in the range of plagioclase found in the unaltered rock. Plagioclase is not common in

the altered rock because it is the first mineral to alter to epidote, chlorite, and sericite

(Sillitoe 2010). The potassium feldspars were much more abundant and are less altered

than the plagioclase. The biotite compositions analyzed in the altered rocks are similar to those

analyzed in the unaltered rock, indicating that all the biotite is unaltered igneous biotite.

Figure 21 shows a BSE image from the microprobe of chlorite replacing biotite. The

biotite originally has a wavy sheet silicate appearance that the chlorite replicates where it

replaced it. Biotite commonly contains trace amounts of titanium and the analysis of the

Figure 23: Ternary diagram displaying the varying compositions found in the propylitic suite. Circled is the fresh granite plagioclase. Ab=Albite, Or=Orthoclase, An=Anorthite.

Haggart 21

fresh Butte quartz Monzonite,

as well as the biotite in the

altered rocks, found roughly 2.5

weight percent of Ti present in

the structure (table 2).

The sphene in the

alteration chlorite has a range

of compositions (Ca1.133-

0.914Ti0.699-0.701Si1.034-0.962Al0.258-

0.197Fe0.118-0.099Mg0.093-0.0829O5).

Most of the elements in the

sphene composition originate

from the original biotite that is

being altered with the exception

of calcium. The large quantities of calcium needed to form sphene brings up the

interesting question of where it originates from. As stated above, it is most likely that the

calcium is freed from altered plagioclase and the calcium ions diffuse towards fractures.

This is the most likely scenario because every sample I examined has almost every

plagioclase altered to some degree, thus providing the calcium needed to form the

sphene.

Calcium could be supplied to sphene that is very close to fractures by

hydrothermal fluids. Along the veins in sample 534 (figure 5 and 6) there are abundant

concentrations of sphene, which is most likely due to a large supply of calcium in the

nearby hydrothermal fluid. Because of the close proximity it is likely that the calcium

diffused from the fracture, but many of the alterations examined are found millimeters to

centimeters away from the nearest fracture which is too great of a distance for calcium

diffusion.

Originally when viewed under a transmitted light microscope sphene was

misidentified as an oxide mineral due to the opaqueness of the mineral. Multiple analyses

on the SEM and the EMPA confirm that the opaque mineral in thin section is sphene.

Sphene usually displaces a low order birefringence, except when it has 1% Fe content or

Figure 24: From sample 383. The lighter shade of gray is biotite while the surrounding darker gray is chlorite. The lighter shade implies a heavier mean atomic number than the darker. The sphene is the lightest shade due to the concentration of titanium in the mineral. Chlorite can be seen replicating the wavy pattern of the original biotite. The red circles represent points selected for analysis on the EMPA.

Haggart 22

higher (Deer, 1992). Table 5 shows that the Fe content of three different sphene crystals

range from 1.7 to 3.3 percent, which causes it to appear black or opaque in thin section.

Epidote compositions vary slightly where it lies distal from veins, but has

significantly more calcium where it is immediately next to a vein. Next to a vein the

composition is Ca3.1195Al2.477Fe0.828Mn0.26Si3.1195 and away from the vein the calcium

drops to 2.1 cations. The increase in Ca content in the sphene that forms near the veins is

evidence for a calcium rich hydrothermal fluid that originally flowed through the

fractures. Distal sphene has a lower calcium concentration, which is contributed to lower

supply of calcium from the alteration of plagioclase.

Chlorite Geothermometer

There have been many chlorite geothermometers proposed over the years based

on varying criteria. The chlorite geothermometer reviewed by Caritat et al. provides

multiple techniques for using chlorite as a geothermometer. The first empirical formula

attempted in this study was one derived by Cathelineau (1987). The relationship between

temperature and AlIV was computed to be:

𝑇 = −61.92 + 321.98𝐴𝑙𝐼𝑉

This equation is supposed to be applicable in diagenetic, hydrothermal, and metamorphic

settings (Cathelineau 1987), but was found to have little value with the chlorite

compositions in this study. Equation 1 resulted in temperatures ranging from 600°C to

800°C, which is much higher than the expected 340°C.

Kranidiotis and Maclean offered a correction to Cathelineau’s work by taking in

account the variation in Fe/(Fe+Mg). As iron is increased in chlorite AlIV also increases

with little or no change to the Al in the octahedral site (Kranidiotis & MacLean 1987). To

correct for this a new AlIV is computed using equation 2.

𝐴𝑙𝐶𝐼𝑉 = 𝐴𝑙𝐼𝑉 + 0.7(

𝐹𝑒

𝐹𝑒 +𝑀𝑔)

The temperature is then computed using equation 3, which is calibrated for pressures

ranging from 100-700 bars. Based on previous studies the pressure of the Butte samples

falls within this range.

𝑇 = 106𝐴𝑙𝐶𝐼𝑉 + 18

Equation 1

Equation 2

Equation 3

Haggart 23

(Caritat). I applied this method on the new set of data from Butte, Montana and obtained

more reasonable temperatures. The temperatures range from 253° C to 321° C with the

higher end being a primary chlorite that formed in the vein (graph 2). Un 14 and Un 12

are also primary chlorites from veins and, as expected, Un 12 yields a higher temperature.

Un 13 is also a primary chlorite and is calculated to have formed at 272° C which is

lower than the other two, but is still feasible if it formed at a later stage once the fluids

had already begun to cool.

A third empirical formula was derived by Jowett (1991) in which another

correction derived from an isothermal Fe/(Fe+Mg) ratio normalized based on their data

from the Salton Sea and Los Azufres. Their new equation is supposed to able to find

temperatures for chlorites that formed between 150°C and 325°C (Patrice and Walshe,

1993). When applied to the set of data collected from Butte the temperature ranges

calculated were from 620°C to 720°C. The temperatures reported are far out of the range

of the expected 340°C to 350°C.

A new chlorite geothermometer has been proposed by Bourdelle et al. for

diagenetic to low-grade metamorphic chlorites. Unlike the chlorite geothermometers

based solely on stoichiometry, this new method uses thermodynamics to find the

temperatures the chlorites formed at (Bourdelle 2013). The geothermometer has been

tested and proved accurate for conditions where the temperature is less than 350°C and

less than 4kbar of pressure. Chlorites from the Butte propylitic suite fit in these

Graph 2: All temperatures calculated using equations 2 and 3 then plotted against their depths. Sample 12,13, and 14 are primary chlorite while the rest are alteration chlorites. Temperatures fall within the expected range of 220 to 340 degrees Celsius.

0

100

200

300

400

500

600

250 270 290 310 330D

epth

(m

)Temperature (C)

Temperture vs. Depth

Un 4

Un 7

Un 12

Un 13

Un 14

Un 20

Un 24

Haggart 24

conditions, making them a good candidate for this geothermometer. Once applied it could

give a clearer picture of the temperatures at which chlorite replaces biotite in

hydrothermal systems similar to the one that created this porphyry copper depsosit.

Conclusions

Alteration in the propylitic zone in porphyry copper deposits is not as extreme as

found in other zones, but it still offers insight into how porphyry copper deposits form as

a whole and the fluids that form them. As the alteration of titaniferous biotite to chlorite

occurs sphene forms, owing to increase concentrations of titanium. The release of

calcium from altered plagioclase provides the calcium needed to form the sphene and

epidote that occurs near the chlorite alterations. An abundance of epidote and sphene

around veins could indicate a high supply of calcium from the hydrothermal fluids, which

gives further insight into the composition of the fluids.

The sphene found throughout the propylitic zone exhibits uniquely different

behaviors than expected. It forms as a pseudomorph of biotite, which is uncommon for

the sphene structure, as well as appearing opaque in thin section. The pseudomorphism

could be due to the low temperatures it formed at, thus not allowing it to form the blocky

shape it usually takes. The temperature of formation could also be a controlling factor on

the amount of iron that substitutes into the structure causing it to appear black in thin

section. Uranium can also substitute into the structure for calcium which in theory could

be used for dating of the rock (reference), giving a more accurate time of formation for

the deposit as a whole.

In this study the geothermometer created by Cathelineau did not prove to be

accurate or reliable, but the revised version created by Kranidiotis did prove to be more

realistic. It cannot be said with absolute certainty that the temperatures recorded are

correct, due to the lack of available information of the formation temperatures, but 280°

to 360° is a more expected temperature ranged based on previous research. The new

geothermometer created by Bourdelle et al. uses a semi-empirical model which appears

to provide a more accurate temperature for conditions under 350°C.

Haggart 25

Na

me

S

i W

T%

T

i W

T%

A

l W

T%

F

e W

T%

M

n W

T%

M

g W

T%

C

a W

T%

N

a W

T%

K

WT

%

P W

T%

O

WT

%

H W

T%

Un 4

-

Sam

ple

383

13.4

62

0.3

44

8.7

02

18.2

79

0.5

15

9.5

34

0.0

56

0.0

00

0.8

97

-0.0

05

46.7

55

1.4

59

Un 7

-

Sam

ple

383

12.6

45

0.4

66

9.6

65

18.2

27

0.8

81

10.0

12

0.4

72

-0.0

03

0.0

10

-0.0

04

46.2

80

1.3

50

Un 1

2 -

Sam

ple

383

11.9

48

0.0

21

10.5

96

20.3

97

1.0

54

8.0

76

0.0

32

0.0

95

0.1

05

-0.0

03

46.2

13

1.4

66

Un 1

3 -

Sam

ple

383

11.7

02

0.0

22

10.5

46

20.5

50

0.9

98

8.2

53

0.0

34

0.0

02

0.1

34

-0.0

03

46.2

65

1.4

98

Un 1

4 -

Sam

ple

383

12.3

43

0.0

26

9.9

49

18.2

41

0.7

83

10.5

99

0.0

23

0.0

04

0.0

26

-0.0

13

46.6

03

1.4

17

Un 2

0 -

Sam

ple

534

12.1

48

0.0

17

10.9

58

13.9

75

0.7

94

12.1

91

0.0

13

0.0

03

0.0

18

-0.0

05

48.3

19

1.5

69

Un 2

4 -

Sam

ple

534

12.2

48

0.0

29

10.3

24

13.9

48

0.8

06

12.1

65

0.0

16

-0.0

01

0.0

45

-0.0

09

48.7

46

1.6

82

Ta

ble

1:

Ch

lori

te c

om

po

sit

ion

s f

rom

th

e s

ec

on

d E

MP

A r

un

. O

xyg

en

an

d h

yd

rog

en

are

ca

lcu

late

d b

as

ed

on

sto

ich

iom

etr

y d

on

e b

y t

he

mic

rop

rob

e s

oft

wa

re.

Haggart 26

Na

me

S

i W

T%

T

i W

T%

A

l W

T%

F

e W

T%

M

n W

T%

M

g W

T%

C

a W

T%

N

a W

T%

K

WT

%

P W

T%

O

WT

%

H W

T%

Un 5

- S

am

ple

383

17.1

7308

2.5

31627

7.0

76002

14.7

3373

0.2

50343

7.1

62036

0.0

12045

0.0

43242

7.7

23579

-0.0

0756

42.7

2546

0.5

76424

Un 1

5 -

Sam

ple

383

16.7

3533

2.6

63094

7.1

6152

14.8

5208

0.2

42569

7.2

34604

0.0

01118

0.0

48185

8.1

7977

-0.0

1299

42.3

4468

0.5

50087

Un 2

1 -

Sam

ple

534

29.5

623

0.0

06601

10.1

137

0.2

49261

0.0

07742

0.0

02236

0.0

0131

0.2

89244

13.9

0653

-0.0

1345

45.8

5353

0.0

21041

Un 2

6 -

Sam

ple

Bu

16.7

528

2.5

56823

6.8

5102

14.1

435

0.1

99606

7.4

65855

-0.0

0218

0.0

72947

8.0

13218

-0.0

1228

43.2

4297

0.7

15743

Un 2

8 -

Sam

ple

Bu

16.8

587

2.5

3176

6.9

7184

14.7

0705

0.2

15847

7.3

3825

0.0

03451

0.0

67864

8.1

47058

-0.0

1183

42.5

786

0.5

91459

Un 3

4 -

Sam

ple

383

16.6

7915

2.4

9936

7.1

79745

15.3

7595

0.4

68961

7.1

1277

0.0

54189

0.0

49125

7.7

2049

-0.0

0886

42.3

12

0.5

57125

Ta

ble

2:

Bio

tite

Co

mp

os

itio

ns

fro

m t

he s

eco

nd

EM

PA

ru

n.

Ox

yg

en

an

d h

yd

rog

en

are

ca

lcu

late

d b

as

ed

on

sto

ich

iom

etr

y d

on

e b

y t

he

mic

rop

rob

e s

oft

wa

re.

Haggart 27

Na

me

S

i W

T%

T

i W

T%

A

l W

T%

F

e W

T%

M

n W

T%

M

g W

T%

C

a W

T%

N

a W

T%

K

WT

%

P W

T%

O

WT

%

H W

T%

Un 9

- S

am

ple

383

29.7

471

-0.0

2074

10.1

2108

0.0

33083

-0.0

016

0.0

00525

0.0

15876

0.4

06344

13.4

6643

-0.0

0985

46.2

5885

0.0

60239

Un 1

7 -

Sam

ple

383

26.3

788

0.0

03257

14.5

7323

0.1

30932

0.0

02271

0.0

03567

5.6

6978

5.1

65507

0.1

66153

0.0

29054

47.8

0083

0.0

76636

Un 1

8 -

Sam

ple

534

25.8

9464

0.0

16509

13.2

3292

1.3

32618

0.0

59363

1.0

25431

0.2

76643

1.7

97972

8.6

07076

-0.0

0682

47.4

373

0.3

26367

Un 2

2 -

Sam

ple

534

29.2

883

-0.0

068

10.5

6485

0.0

67523

-0.0

0374

0.0

01814

0.2

16782

1.5

08544

11.6

5652

-0.0

0727

46.6

078

0.1

05698

Un 2

5 -

Sam

ple

Bu

25.9

679

-0.0

0632

14.4

8115

0.1

42165

-0.0

0097

0.0

05161

6.0

56725

5.1

3519

0.1

87939

0.0

33305

47.8

63

0.1

3478

Un 2

7 -

Sam

ple

Bu

29.2

9888

-0.0

0805

10.1

5711

0.0

68382

-0.0

0178

0.0

01692

0.1

8558

2.4

51825

9.8

3482

-0.0

0341

47.7

1858

0.2

96389

Un 2

9 -

Sam

ple

Bu

29.4

0207

-0.0

0305

10.2

9827

0.0

98498

0.0

01875

-0.0

0056

0.0

57685

1.2

99145

12.2

891

-0.0

1176

46.4

671

0.1

01688

Un 3

1 -

Sam

ple

Bu

25.3

4755

0.0

18347

14.8

6345

0.2

54526

-0.0

0009

0.0

07755

6.6

7882

4.5

2835

0.2

89467

0.0

37735

47.8

1365

0.1

60368

Ta

ble

3:

Fe

lds

pa

r c

om

po

sit

ion

s f

rom

th

e s

ec

on

d E

MP

A r

un

. O

xyg

en

an

d h

yd

rog

en

are

ca

lcu

late

d b

as

ed

on

sto

ich

iom

etr

y d

on

e b

y t

he

mic

rop

rob

e s

oft

wa

re.

Haggart 28

Na

me

S

i W

T%

T

i W

T%

A

l W

T%

F

e W

T%

M

n W

T%

M

g W

T%

C

a W

T%

N

a W

T%

K

WT

%

P W

T%

O

WT

%

H W

T%

Un 1

0 -

Sam

ple

383

17.0

011

0.0

60546

12.6

1492

9.0

96722

0.4

03564

0.2

28427

16.0

6927

-0.0

0013

0.3

15093

0.1

42902

43.6

3142

0.4

3621

Un 1

9 -

Sam

ple

535

16.8

4039

0.0

19207

12.8

4779

8.8

89775

0.2

77025

0.0

29499

16.5

9608

-0.0

0768

0.0

06273

0.1

23238

43.8

9498

0.4

83478

Un 2

3 -

Sam

ple

534

17.2

178

0.0

07795

12.5

6448

9.2

4869

0.1

19564

0.0

40605

16.2

1925

0.3

35105

0.0

16063

0.1

07439

43.6

8908

0.4

34208

Un 3

2 -

Sam

ple

534

16.7

4364

0.0

01627

12.7

707

9.5

84056

0.1

20045

0.0

36556

16.6

9868

-0.0

0025

0.0

08891

0.1

02598

43.4

9808

0.4

35391

Un 3

3 -

Sam

ple

383

16.5

7175

0.0

33356

12.1

6295

10.3

858

0.5

40727

0.0

27886

16.2

726

-0.0

0257

-0.0

0032

0.1

03801

43.4

1155

0.4

92531

Ta

ble

4:

Ep

ido

te C

om

po

sit

ion

s f

rom

th

e s

ec

on

d E

MP

A r

un

. O

xyg

en

an

d h

yd

rog

en

are

c

alc

ula

ted

ba

sed

on

sto

ich

iom

etr

y d

on

e b

y t

he

mic

rop

rob

e s

oft

wa

re.

Haggart 29

Ta

ble

5:

Sp

he

ne

Co

mp

os

itio

ns

fro

m t

he

sec

on

d E

MP

A r

un

. O

xyg

en

an

d h

yd

rog

en

are

ca

lcu

late

d b

ase

d o

n

sto

ich

iom

etr

y d

on

e b

y t

he

mic

rop

rob

e s

oft

wa

re.

Na

me

S

i W

T%

T

i W

T%

A

l W

T%

F

e W

T%

M

n W

T%

M

g W

T%

C

a W

T%

N

a W

T%

K

WT

%

P W

T%

O

WT

%

H W

T%

Un 6

-

Sam

ple

383

13.3

1865

16.6

645

2.6

2238

1.7

0007

0.0

18055

0.0

32362

22.3

8975

-0.0

0442

0.0

71714

2.0

46327

41.0

967

0.0

43997

Un 8

-

Sam

ple

383

14.6

0677

16.8

7627

3.4

99337

3.2

9957

0.1

16799

1.1

32758

18.4

2733

0.0

06367

0.0

15028

0.1

53789

41.6

9237

0.1

7363

Un 1

6 -

Sam

ple

383

13.8

8873

17.8

8793

3.3

27753

2.7

5871

0.1

06022

1.0

05513

19.0

9463

-0.0

0632

0.0

16376

0.1

47324

41.5

7847

0.1

94907

Haggart 30

SA

MP

LE S

i WT%

Mg

WT%

Fe

WT%

Al W

T% C

a W

T% N

a W

T%

K W

T% T

i WT%

Mn

WT%

Cl W

T%

Ch

lori

te (

1)13

.472

0411

.614

6412

.499

5210

.529

120.

0191

648

0.00

5760

80.

0683

342

0.01

1129

80.

5773

848

0.01

6319

2

Bio

tite

(1)

17.4

8738

57.

3905

6923

111

.522

6069

8.02

8033

080.

0151

2862

0.07

3527

696.

9630

154

2.27

8056

20.

4885

6561

50.

1828

3192

Bio

tite

(2)

17.7

5826

77.

7178

8666

710

.540

1458

8.10

6215

0.01

6331

670.

0686

7042

7.18

6595

82.

1450

858

0.51

5326

0.18

1483

25

Feld

spar

(1)

25.0

2416

70.

4569

9483

31.

2251

5842

13.8

9889

170.

1707

2575

0.12

8179

257.

8644

80.

0036

285

0.01

5869

50.

0218

4783

Feld

spar

(2)

30.2

324

-0.0

0037

292

0.06

8645

699.

1450

4077

0.01

9461

920.

4546

3477

13.2

4689

20.

0252

401

-0.0

0122

308

0.02

1321

62

Bio

tite

(1)

17.3

884

6.89

8048

9.36

1052

8.75

4334

0.04

4819

40.

0618

274

7.25

775

2.56

4788

0.40

5455

80.

0904

544

Ap

atit

e0.

1982

660.

0140

435

0.08

4650

50.

0539

8738

.607

50.

0233

495

0.11

5993

0.00

9359

50.

0900

450.

2385

47

Bio

tite

(2)

15.1

1374

9.38

6892

10.9

729

10.8

0682

20.

0528

376

0.01

1038

81.

1608

694

0.17

0675

60.

4993

850.

0349

7

Bio

tite

(3)

16.4

4726

7.82

251

10.5

9547

810

.356

910.

0334

116

0.03

8785

23.

3865

184

1.03

1962

0.48

0892

20.

0993

43

Bio

tite

(4)

17.3

6652

8.04

8288

9.97

0785

8.62

895

0.01

5377

40.

0432

787

8.17

859

0.84

9774

40.

4499

151

0.10

0168

7

Ta

ble

6:

Ru

n 1

EM

PA

an

aly

sis

of

sa

mp

le 6

20.

Haggart 31

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