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  • TBE PETROLOGY, GEOCaEMISTRY AND PETROGENESIS OF TElE m A K A COMPLEX, S o m ISLAND, NEW ZEALGND.

    BY Jeff'y Keith Saunders, B.Sc (Hoor)

    A Thesis Submitîed to the School of G r d a t e SIudies in Parrial FurjFZrnent of the Requirements for the degree

    of Master of Science

    Department of &th Sciences, Mernorial University of Nwmncild

    St. John 's

  • National Library Bibliothèque nationale du Canada

    Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Weiiimgtm Street 395, rue Wellingtor, -ON K l A W OrrawaON K I A W canada Canada

    The author has granted a non- L'auteur a accordé une Licence non exclusive licence allowing the exclusive pemettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of this thesis in microform, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/film, de

    reproduction sur papier ou sur format élecîronique.

    ïhe author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantid extracts fkom it Ni la thèse ni des extraits substantie1s may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation.

  • Frontispiece: The Graham Vailey From the Motueka River vailey.

  • ABSTRACT

    The Riwaka Complex is a tholeütic igneous intrusion (40km long, up to several km

    wide) located in the northwestern part of the South Island of New Zealand. it intrudes the

    Takaka Terrane which represents an assemblage of sedimentary rocks that are part of New

    Zealand's geologic Western Province. The Takaka Terrane is thought to have fonned in a

    fore - arc enviromnent associated with either one or two westward dipping Benioff zones.

    In this subduction zone environment the tholeiitic magma crystaUized in a manner

    similar to that, that fonn AIaskan - type ultrarnafic complexes. Its distinctive petrological

    features include: cumulate o h e and clinopyroxene and interstitial amphibole; absence of

    orthopyroxene and plagioclase; and M e or no Fe - enrichment, but a Ca - enrichment in

    the clinopyroxenes. The Riwaka Cornplex's geochemical evolution was dominated by

    olivine and clinopyroxene fiactionation Eom as many as five pulses of magma, which gave

    rise to an intrusion made up alrnost entirely of ultramafic rocks ranging fiom

    clinopyroxene - bearing du&es to olivine - homblende clinopyroxenites. Some minor gabbros and diontes are also present.

    The srnail amount of gabbro present represents an important part of the Riwaka

    Complex as these rocks contain sigdicant amounts of prirnary sulphides which are rich in

    nickel, copper and platinum group elements. The nickel and copper ratios indicate that the

    composition of the parental magma was similar to that of a komatiite. This magma

    wolved to a basaitic type composition which gave rise to the gabbroic rocks. The high

  • temperature platinum group elements (Os, Ir and Ru) are not found in the same

    abundances within the gabbroic rocks as th& lower temperature cornterparts (Rh,

    Pt and Pd) indicating that they have undergone an earlier hctionation, possibly within the

    eariy crystallized uitramafic rocks. These rocks may therefore represent an important

    exploration target.

  • There are numerous indMduals who require acknowledgement for their contn ion to this study. F ' i y , I would Wce to thank Dr. John Malpas who initiated and superviseci this project. His financial support, niendslip and patience throughout the course of this study are greatly appreciated. A h , Dr. Derek W&on who served on my supervisory commiffee and made time in his busy schedule to proof read this thesis.

    In New Zeatand, 1 would like to thank Dr. Tan Smith for anmghg use of the facilities at the University of Auckland and Mr. Mike Johmton of the Departma of Scientific and Industrial Research @SIR) whose discovery of Cu - Ni suiphides in the Riwaka Complex eventuayl led to this study. He ais0 provided me with maps and shared some of bis in - depth knowledge of my field area with me. Nick Mortimer of DSlR in Wehgton provided me with copies of ali the publications concenUng my field area and access to the drillcore samples lomed in DSIR's ddcore storage facility in Christchurch.

    StafFfkom Memonal's Department of Earth Sciences are thanked for their help, especidy noting; Danyl Clarke (XRF), Bev Chaprnan (ICP - MS), Pam King (ICP - MS, X W , probe and other trouble shooting), Me- Goodyear (cornputer support) and Maggy Piranian (probe).

    Students R Churchill, G. Thompson, D. Johnstone, C. Lee, P. Ivany, V. Bennett, K. Deveau, A. and N. Aydin and D. Ritcey made this study take a lot longer than it should have, but made d l of the time much more enjoyable.

    Finally, 1 would like to thank my field assistant and d e Brenda for her patience, support and understandimg during the course of this study.

  • Chapter 3: Field Relrtionsbips and Petmgraphy

    3 - 1 Introduction ............................................................................. .. ............... 36 3.2 htnisive History of the Graham Valley A r a ...........................am................... -36

    3.2.1 Basement rocks ............... .... ........................................ .. ................ -36 3 .2.2 Riwaka Complex ........................................................................... 39 3 .2.3 Late intrusive rocks ....................................................................... -41

    3 -3 Structure of the Riwaka Complex ................................................................. 41 3 .3.1 Deformation within the Riwaka Complex ............................thin....... -41 3 -3 -2 Magmatic structure ........................................................................ 44

    3 -4 Petrography of the Riwaka Cornplex ................. .. ..................................... -45 ...................... .......................................................... 3.4.1 Introduction ,. -45

    3 .4.2 The Fractionation Suite .................................................................. 46 .................................. 3 .4.2.1 Minerals of the Fractionation Suite -48 . .

    3.4.2.1.1 Olivme .............................................................. 48 ................................................... 3 A.2.1. 2 Clinopyroxene 48

    3 A2.1.3 Amphibole ......................................................... 51 3 .4.2.1 -4 Accessory minerals ............................................ 51

    3.4.3 Cumulus Gabbro ........................................................................... -53 ...................................... 3 .4.3.1 MUierals of the Cumulus Gabbro 54 . .

    3.4.3.1.1 Olivine ............................................................. -54 .................................................. 3.4.3.1.2 Chopyroxene -54

    3 .4.3.1 -3 Amphibole ......................................................... 55 ........................... .......................... 3 .4.3.1 -4 Plagioclase ... 55

    .............................................. 3.4.3.1.5 Sulphide minerals 55 .......................................... 3.4.3.1.6 Accessory minerals 56

    3.4.4 Late Stage Diorite ...................... .... ........................................ -56 ................................... 3 .4.4.1 Minerais of the Late Stage Dionte -57

    .................................................. 3 .4.4.1 - 1 Clinopyroxene -57 ......................................................... 3 .4.4.1 -2 Amphibole 57 ........................................................ . 3 .4.4.1 3 Plagioclase 57

    .............................................................. 3 .4.4.1.4 Apatite 57 .......................................... 3 -4 .4.1 -5 Accessory Minerais -58

    3.5 Separation Point Batholith ............................................................................ 58 3 -6 Discussion .............. .. ................................................................................ -59

    3 .6.1 Introduction .................................................................................. -59 . . 3.6.1.1 Ophiolites ....................................................................... -59 3.6.1 . 2 Layered intrusions ........................................................... -61

    . ................................ 3.6.1 3 Alaskan - type dtramafic complexes 63 .............................................. 3 .6.2 The Riwaka Complex in perspective -65

    vii

  • 5 .5 . 3.2 Chondrite - nomialized PGE pattern diagrams ........................................................................ 122

    5.5.3 -3 Metal ratio diagrams ............................................... ... .... 128 5.5.3 -4 Mamle - nomaiized PGE pattern

    diagrams ........................................-.............................. -129 .................................................................................................... 5.6 Summary 130

    Chripter 6: Discussion and Conclusions

    ...................................................................................

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