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首页> 外文期刊>Journal of Volcanology and Geothermal Research2012V243-244NOCT,15 >Nature and origin of tuff beds in Jurassic strata of the Surat Basin, Australia: Implications on the evolution of the eastern margin of Gondwana during the Mesozoic
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Nature and origin of tuff beds in Jurassic strata of the Surat Basin, Australia: Implications on the evolution of the eastern margin of Gondwana during the Mesozoic

机译：澳大利亚苏拉特盆地侏罗纪地层的姜黄床的自然和起源：对中生代期间吉隆坡东部边缘进化的影响

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摘要

Volcanogenic rocks in the Great Australian Superbasin provide one of the principal records of contemporaneous volcanism in eastern Australia during the Mesozoic. However, the paucity of primary Jurassic to Early Cretaceous-age extrusive or intrusive igneous bodies on the Australian continent makes it particularly challenging to deduce their source and character. This, in turn, makes it difficult to ascertain how the eastern margin of Gondwana evolved during this timeframe. Despite some studies of this enigmatic volcanism, there have been little or no detailed analyses of these Jurassic to Early Cretaceous-aged sediments. Based on the multidisciplinary analyses of age-constrained air-fall tuffs (168 to 148 Ma) from the Jurassic Walloon Coal Measures of the Surat Basin, we suggest from zircon grains of a similar age that the tuffs were erupted from volcanoes fed by intermediate to felsic magmas supported by their quartz and feldspars-rich composition, and from zircon grains with low to moderate Nb values (0.5 to 100 ppm) and high U and Th values (30 to 1000 ppm). The mapping of tuff isopachs and a mean zircon crystal size of 170 mu m supports the source being from volcanoes approximately 280 to 1000 km from the palaeoeast-southeast with a volcanic explosivity index (VEI) of 8. Our results indicate the tuffs originated from a continental arc setting associated with the Whitsunday Igneous Association, and the long-lived (late Palaeozoic to Cretaceous) westward subduction of the palaeo-Pacific oceanic crust beneath eastern Australia. Such a tectono-magmatic environment would help constrain the timing of the transition of eastern Gondwana from a convergent to a divergent margin. (C) 2019 Elsevier B.V. All rights reserved.
机译：伟大的澳大利亚Superbasin的火山岩岩石提供了中生代期间澳大利亚东部的同期火山的主要记录之一。然而，澳大利亚大陆的原发性侏罗纪对早期白垩纪的侵犯或侵入性的火药的缺乏使其尤其挑战推断出源头和性格。反过来，这难以确定在这个时间框架期间Gondwana的东部边缘如何发展。尽管对这种神秘的火山主义进行了一些研究，但这些侏罗纪对早期的白垩纪老年人沉积物几乎没有或没有详细分析。根据苏拉特盆地的侏罗纪瓦隆煤措施（168至148 mA）的多学科分析来自苏拉特盆地的侏罗纪山煤措施，我们从锆石谷物的类似年龄的谷物提出，从中级喂养的火山爆发了凝灰岩富尔斯岩浆由其石英和长石的组合物支持，并从锆石颗粒，低于中等NB值（0.5至100ppm）和高U和Th值（30至1000ppm）。 Tuff Isopachs的映射和170 mu m的平均锆石晶粒尺寸支持从火山的源极约280至1000公里，从火山爆炸指数（vei）为8.我们的结果表明牙龈起源于a与Whitsunday Igneous协会相关联的大陆弧环境，以及澳大利亚东部地区古古城海壳的长寿（已故古生代）向西俯冲。这种构造的魔法环境将有助于限制东巩膜的过渡到从趋同到发散边缘的时间。 （c）2019 Elsevier B.v.保留所有权利。

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