Geology of Flat Hill-Ocean Beach, Bluff Peninsula

Author:

Elder, Damon Jon.

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Abstract:

In the Bluff area lower green schist facies Greenhills Group rocks of the Brook Street terrane derived from a Permian volcanic arc have been intruded ~ by igneous bodies inducing contact metamorphism. Facies of contact metamorphism are observed as pyroxene hornfels facies in assimilated xenoliths in a hybrid rock zone, further out from the intrusions hornblende hornfels are observed. At a distance of 800 m from the intrusive contacts albite-epidote facies of contact metamorphism are observed in metabasaltic dykes. Evidence for this facies comes from the mineral assemblages in the metabasalt dykes which have cut vertically through Greenhills Group metasediments very soon after the tilting of the Greenhills Group bedding associated with the intrusion of the large igneous bodies. The intrusive bodies are the Flat Hill gabbronorite and the Ocean Beach diorite which show a distinct difference in the bulk rock chemistry with the diorite appearing as a· more evolved rock. Dyke intrusion of microgabbro, quartz diorite and hornblende pegmatite is part of late stage activity associated with the cooling of the large igneous~ bodies. Granitic dykes present post date the intrusion of the large igneous bodies and the late stage dyke activity. The age of the Flat Hill gabbronorite is given as 265 M a, the oldest recorded rocks of the Brook Street terrane. - --l J

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71 p. : ill. (some col.), maps (some col.) ; 30 cm.

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OU geology Identifier:

1994Elder

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Location (WKT, WGS84):

POLYGON ((168.324185158000091 -46.590544009999974,168.324049425000112 -46.592147125999986,168.323314835000019 -46.600719178999952,168.318124152000109 -46.600528732999976,168.315823832000092 -46.600442774999976,168.311861722000117 -46.60029586,168.270814986000119 -46.598762532999956,168.272078617000034 -46.584858797999971,168.273326607000058 -46.571134626999935,168.273585456000092 -46.568270304999942,168.273651605000055 -46.567556534999937,168.274153460000093 -46.562016493999977,168.274390102000098 -46.559417117999942,168.276695517000121 -46.559499676999963,168.29353061200004 -46.560099362999949,168.300554472000044 -46.560349990999953,168.304371169000092 -46.560482666999974,168.326681021000013 -46.561270885999932,168.324483232000034 -46.58705497699998,168.324475441000118 -46.587149285999942,168.324395751000111 -46.588074279999944,168.324389444000076 -46.588150624999969,168.32437311800004 -46.588348223999958,168.324185158000091 -46.590544009999974))

Files

http://download.otagogeology.org.nz/temp/Abstracts/1994Elder.pdf

Collection

Citation

Elder, Damon Jon., “Geology of Flat Hill-Ocean Beach, Bluff Peninsula ,” Otago Geology Theses, accessed May 22, 2024, https://theses.otagogeology.org.nz/items/show/295.

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