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Title: Time controlled geochemistry of igneous rocks of the Antarctic Peninsula
Author: Hole, Malcolm John.
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 1986
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Four distinct groups of intrusive rocks have been identified within Graham Land, northern Antarctic Peninsula. Each Group is defined on the basis of age, Sr-, Nd- and a-isotopic and trace element geochemical signatures. Group I intrusions are dominantly Tertiary and are geographically restricted to the W coast of the Peninsula, and exhibit low initial e7Sr/e6Sr and high initial 14~Nd/144Nd ratios (0.7038 - 0.7045 and 0.51280 0.51277). Group I intrusions possess the lowest LIL/HFS ratios of any Group with Th/Ta and La/Ta ratios similar to N-type MORB, and may exhibit a distinct alkaline affinity; they are considered to have been emplaced during a Tertiary supra-subduction zone extensional episode. Cretaceous Group II granitoids crop out throughout Graham Land. Group III and IV granitoids range from late Triassic - Jurassic and are restricted to central eastern Graham Land and SE Graham Land respectively. Sr- and Nd-isotope characteristics of Group III and IV intrusions are consistent with base of crust (~35 Km) interaction between a mantle derived magma and pre-TriaSSiC, but not necessarily ancient, continental crust. Group III granitoids possess consistent e7Sr /e6Sr and 14~Nd/144Nd ratios (0.7060 - 0.7070 and ~ 0.5123 respectively). Group IV intrusions are more highly contaminated (initial e7Sr /e6Sr and 14~Nd/144Nd ratios 0.7078 - 0.7162 and 0.5123 - 0.5120 respectively), and were probably intruded through thicker crust than Group III. LIL/HFS and LREE/HREE ratios increase with increasing degrees of contamination.- Isotope and trace element characteristics of Antarctic Peninsula intrusions reflect changes in tectonic regime with time; pre-Triassic tectonic segmentation of Graham Land resulted in the varying degrees of contamination of Groups III and IV, while syn-subduction extension resulted in the emplacement of isotopically uncontaminated Group I intrusions, with calc-alkaline to alkaline affinities.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available