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首页> 外文期刊>Geochemical Journal >Single-grain detrital muscovite Rb-Sr isotopic composition as an indicator of provenance for the Carboniferous sedimentary rocks in northern Dabie, China
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Single-grain detrital muscovite Rb-Sr isotopic composition as an indicator of provenance for the Carboniferous sedimentary rocks in northern Dabie, China

机译：单颗粒碎屑白云母Rb-Sr同位素组成可作为中国大别北部石炭系沉积岩物源的指标

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摘要

Low-grade metamorphic Paleozoic sedimentary rocks are exposed along the northern margin of file Qinling-Dabie orogenic belt that formed by the collision of the North and South China blocks during file Early Mesozoic. Geological provenance and tectonic setting of these low-grade sedimentary rocks are strongly debated. Recent Studies have shown that they contain Paleozoic, Late Proterozoic and Late Archean detrital zircons, which points to an origin from different Sources including rocks from the South and North China blocks. This study presents single-grain mineral Rb-Sr results for detrital muscovites and biotites from Carboniferous sedimentary sequences of the Beihuaiyang low-grade metamorphic zone exposed along the northern margin of the Dabie Mountains. About 15% of detrital muscovite grains are phengitic in composition with high Si/Al ratios of >3.3. Single grain Rb-Sr isotopic analyses show that both muscovites and phengites give it pooled age of about 420 Ma, implying Middle Paleozoic thermal and high-pressure metamorphic events in the source area(s). Rb-Sr isotopic evidence from detrital biotites Suggests at least two different sedimentary sources of old crustal rocks and juvenile material. The latter probably comprised magmatic rocks related to the Paleozoic convergence along the southern margin of the North China block. Whole-rock Sm-Nd isotopic composition of the sedimentary rocks also demonstrates a mixture of sedimentary sources of different ages that confirm conclusions proposed previously from evidence of detrital zircon ages. We conclude that the Paleozoic detrital phengites originate from Paleozoic subduction and Subsequent collision proposed for the North Qinling terrane. Our study shows that, single-grain detrital mica Rb-Sr isotopic characteristics can be a potential indicator for file provenance of geological complex terranes.
机译：低品位的变质古生界沉积岩沿秦岭—大别造山带北缘暴露，该带是由中，早生代期间华北和华南地块碰撞形成的。这些低品位沉积岩的地质起源和构造环境受到了激烈的争论。最近的研究表明，它们包含古生代，晚元古代和晚太古代碎屑锆石，这些锆石指向不同的来源，包括华南和华北地块的岩石。本研究提供了沿大别山北缘暴露的北淮阳低品位变质带石炭纪沉积序列碎屑白云母和黑云母的单粒矿物Rb-Sr结果。约15％的碎屑白云母晶粒具有高Si ​​/ Al比（> 3.3）的成分。单晶Rb-Sr同位素分析表明，白云母和锂铁矿均使其聚集年龄约为420 Ma，这意味着源区中古生代热变质和高压变质事件。碎屑黑云母的Rb-Sr同位素证据表明，至少有两种不同的旧地壳岩石和少年物质的沉积源。后者可能包括与华北地块南缘古生代收敛有关的岩浆岩。沉积岩的全岩Sm-Nd同位素组成也显示了不同年龄的沉积物源的混合物，证实了先前从碎屑锆石年龄的证据得出的结论。我们得出的结论是，古生代碎屑变质岩起源于古生代俯冲作用和随后为北秦岭地层提出的碰撞。我们的研究表明，单粒碎屑云母Rb-Sr同位素特征可能是地质复杂地层文件来源的潜在指标。

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