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首页> 外文期刊>Journal of Asian earth sciences >Generation of Late Cretaceous silicic rocks in SE China: Age, major element and numerical simulation constraints
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Generation of Late Cretaceous silicic rocks in SE China: Age, major element and numerical simulation constraints

机译：中国东南部晚白垩世硅质岩的生成：年龄，主要元素和数值模拟约束

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Rhyolite-dominating bimodal volcanic suites (rhyolite/basalt), mafic dikes and A-type granites distribute from N Zhejiang to S Fujian over 800 km in the Southeast Coast Magmatic Belt (SCMB) - the Late Yanshanian (LY) orogenic belt in SE China. Data of ~(40)Ar/~(39)Ar and K-Ar whole-rock ages and LA-ICPMS U-Pb zircon ages indicate that rhyolitic volcanism (101-72 Ma) is contemporaneous with the A-type granitic intrusions (100-90 Ma) and mafic dike injections (94-77 Ma). This time span is used to define the upper volcanic series in Zhejiang-Fujian areas. One striking feature of rhyolites in the SCMB is that many are strongly peraluminous (SP) and others, mostly restrict in Fujian, are peralkaline to mildly peraluminous (P-MP) and chemically resemble A-type granites. The SP character is unique among well-known large rhyolite provinces worldwide. Based on experimental works for a common thermal regime and inherited zircon age information, we suggest that SP and P-MP rhyolites represent low pressure melting of the felsic (quartzofeldspathic) granite (±metapelite) and the accompanied granodioritic, tonalitic and trondhjemitic member of the core complex assemblage, respectively, to account for the decreasing aluminosity. They could have also been contaminated by young igneous rocks, and ancient crust to a lesser degree, during ascent to the surface. Plate subduction and lithosphere extension processes, respectively, are numerically simulated for the magma generation of these rhyolites using the mafic underplating model. Results suggest that the most effective controlling factor to generate SP and associated P-MP (A-type) magmas during 95-80 Ma is thinning of the lithosphere thickness with a high exhumation rate. Under this circumstance, the core complex assemblage can be uplifted to lower level of the crust and match the constraint of experimental works.
机译：流纹岩为主的双峰火山岩（流纹岩/玄武岩），镁铁岩堤坝和A型花岗岩在东南沿海岩浆带（SCMB）-中国燕山晚期（LY）造山带中，从浙江北部到福建南部分布超过800公里。 。 〜（40）Ar /〜（39）Ar和K-Ar全岩时代以及LA-ICPMS U-Pb锆石年龄的数据表明，流纹质火山活动（101-72 Ma）与A型花岗岩侵入体同时期（ 100-90 Ma）和黑手党堤防注射（94-77 Ma）。该时间跨度用于定义浙闽地区的上层火山序列。 SCMB流纹岩的一个显着特征是，许多是高铝质（SP）的，而其他大多数是福建省限的，是高碱性至轻度铝质（P-MP）的，化学性质类似于A型花岗岩。在全球知名的大型流纹岩省份中，SP字符是独一无二的。基于对普通热态的实验工作并继承了锆石的年龄信息，我们建议SP和P-MP流纹岩代表长晶质（季生辉石）花岗岩（±变石）及其伴生的花岗闪长，变色和变白垩纪成员的低压熔融。核心复合体组件，分别用于解决铝含量降低的问题。在上升到地面时，它们还可能被年轻的火成岩和古老的地壳所污染。利用镁铁质底板模型，分别对这些流纹岩的岩浆生成进行了板块俯冲和岩石圈扩展过程的数值模拟。结果表明，在95-80 Ma期间产生SP和相关的P-MP（A型）岩浆的最有效控制因素是岩石层厚度变薄且高掘出速率。在这种情况下，可以将核心复杂组合物提升到地壳的较低水平，并与实验工作的约束相匹配。

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