Petrology and geochronology of the volcaniclastic and volcanogenic Mesozoic Loch Burn Formation in eastern Fiordland, New Zealand
Petrology and geochronology of the volcaniclastic and volcanogenic Mesozoic Loch Burn Formation in eastern Fiordland, New Zealand
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新西兰峡湾东部火山碎屑和火山成因中生代 Loch Burn 地层的岩石学和地质年代学
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发表时间：
2008
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通讯作者：
A. Cooper
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作者：
J. Scott;I. Turnbull;T. Ewing;A. Allibone;J. Palin;A. Cooper
峡湾东部的洛赫伯恩组是侏罗纪至早白垩世火山弧长期变质和侵蚀的喷发产物。Meta火山碎屑成分中的残留沉积特征表明，沉积作用主要发生在陆地或浅水环境中，该环境由来自近端花岗岩和火山高点的泥石流提供。在默奇森山脉，沉积受到c。342 Ma花岗岩，不整合地覆盖在洛赫伯恩组之上;侵入洛赫伯恩组的158 Ma石英闪长岩。后一个年龄是8-9百万年。比来自洛赫伯恩组的火山碎屑和之前来自斯图尔特山脉的砂岩层更古老，因此支持之前的建议，即洛赫伯恩组是一个长期存在的时间海侵单元。石炭纪基底为变质沉积物中的碎屑锆石、侵入石英闪长岩中的继承锆石和地层中的一些花岗岩类碎屑提供了潜在的物质来源。地球化学之间的相似性石英diaphragm，火山碎屑内的洛赫烧伤形成，和附近的侏罗纪至早白垩世Darran套房岩体意味着洛赫烧伤形成的火山相当于Darran套房。洛赫伯恩组独特的岩性、地球化学、年代和内部关系也见于峡湾北方的火山沉积岩拉格斯群和斯图尔特岛的帕特森群，这表明这三个单元在岩性和年代学上彼此相当。洛赫伯恩组提供了峡湾东部构造演化的全面记录，其中有几个隆起和埋藏事件。它们是：石炭纪深成基底的抬升和侵蚀。195 Ma;洛赫伯恩组序列的较老部分在158 Ma被Darran套岩体埋藏和侵入之前在侏罗纪沉积;沉积至少持续到148 Ma;整个洛赫伯恩组在绿片岩和角闪岩相条件下变质;上覆始新世沉积物隆起、侵蚀，然后沉积;在第三纪Te Anau和Waiau盆地下重新埋藏至沸石相深度;上新世最终隆起。
Abstract The Loch Burn Formation in eastern Fiordland is the metamorphosed and eroded effusive product of a long‐lived Jurassic to Early Cretaceous volcanic arc. Relict sedimentary features within meta‐volcaniclastic components indicate sedimentation in a mostly terrestrial or shallow‐water environment that was fed by debris flows from proximal granitic and volcanic high points. In the Murchison Mountains, deposition is constrained by a c. 342 Ma granite, which is unconformably overlain by the Loch Burn Formation, and a c. 158 Ma quartz diorite that intrudes the Loch Burn Formation. This latter age is 8–9 m.y. older than a volcanic clast from Loch Burn Formation and a sandstone horizon previously dated from the Stuart Mountains, and therefore supports previous suggestions that the Loch Burn Formation is a long‐lived and time‐transgressive unit. The Carboniferous basement provides a potential source for detrital zircon in metasediment, inherited zircon in the intrusive quartz diorite, and some granitoid clasts within the formation. Geochemical similarities between the quartz diorite, volcanic clasts within the Loch Burn Formation, and nearby Jurassic to Early Cretaceous Darran Suite plutons imply that the Loch Burn Formation is the volcanic equivalent of the Darran Suite. The distinctive lithological, geochemical, age, and internal relationships of the Loch Burn Formation are also seen in the volcano‐sedimentary Largs Group of northern Fiordland and Paterson Group of Stewart Island, suggesting that these three units are lithological and chronological equivalents to one another. The Loch Burn Formation provides a comprehensive record of the tectonic evolution of eastern Fiordland, with several episodes of uplift and burial. These are: uplift and erosion of a Carboniferous plutonic basement by c. 195 Ma; deposition of the older part of the Loch Burn Formation sequence in the Jurassic before burial and intrusion by Darran Suite plutons at 158 Ma; deposition continuing until at least 148 Ma; metamorphism of the entire Loch Burn Formation at greenschist and amphibolite facies conditions; uplift, erosion, and then deposition of the overlying Eocene sediments; reburial to zeolite facies depths beneath the Tertiary Te Anau and Waiau Basins; final uplift in the Pliocene.