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首页> 外文期刊>Lithos: An International Journal of Mineralogy, Petrology, and Geochemistry >Early Permian post-collisional high-K granitoids from Liuyuan area in southern Beishan orogen, NW China: Petrogenesis and tectonic implications
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Early Permian post-collisional high-K granitoids from Liuyuan area in southern Beishan orogen, NW China: Petrogenesis and tectonic implications

机译：中国西北山北造山带柳源地区早二叠世碰撞后的高K花岗岩：成因及构造意义

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摘要

Early Permian magmatism is one of the most important tectonothermal events in the Central Asian Orogenic Belt (CAOB). Early Permian granitic magmatism has been recognized from southern Beishan, NW China and they were emplaced between 275 Ma and 279 Ma according to LA-ICPMS zircon U-Pb dating. They are mainly metaluminous I-type and belong to the high-K calc-alkaline and shoshonitic series. The granitoids have calc-alkalic and alkali-calcic features. Their Sr_i values range from 0.7028 to 0.7047, ε _(Nd)(t) values from — 2.5 to +1.2 with Nd model ages (T_(DM)) of 1.06-1.25 Ga, suggesting a mixed magma source of juvenile material with old continental crust Furthermore, some granitoids have weak heterogeneous zircon ε _(Hf)(t) values (—1.7 to + 9.6) and Hf model ages (T_(DM2)= 0.84-1.57 Ga) that are also indicative of juvenile components with a small involvement of old continental crust. Based on geochemical and isotopic features, these high-K granitoids were derived from melting of heterogeneous crustal sources or through mixing of old continental crust with juvenile components and minor AFC (assimilation and fractional crystallization). The juvenile components probably originated from underplated basaltic magmas in response to asthenospheric upwelling. These Early Permian high-K calc-alkaline granitoids in the southern Beishan orogen were probably emplaced in a post-collisional extensional setting and suggest vertical continental crustal growth in the southern CAOB, which is the same or similar to most granitoids in CAOB. This study provides new evidence for determining the post-accretionary evolution of the southern CAOB.
机译：二叠纪早期岩浆活动是中亚造山带（CAOB）中最重要的构造热事件之一。早二叠纪花岗岩浆岩已从中国西北部的北部山区被发现，根据LA-ICPMS锆石U-Pb年代，它们位于275 Ma至279 Ma之间。它们主要是金属I型，属于高K钙碱性和肖氏铁系列。花岗岩类具有钙碱性和钙碱性特征。它们的Sr_i值介于0.7028至0.7047之间，ε_（Nd）（t）值介于-2.5至+1.2之间，且Nd模型年龄（T_（DM））为1.06-1.25 Ga，表明幼年材料与旧岩浆的混合岩浆源此外，一些花岗岩类的锆石ε_（Hf）（t）值较弱（-1.7至+ 9.6），Hf模型年龄（T_（DM2）= 0.84-1.57 Ga）也表明其幼体具有小块的旧大陆壳。基于地球化学和同位素特征，这些高K花岗岩来自异质地壳源的熔融，或通过将旧大陆壳与幼年成分和少量AFC（同化和分级结晶）混合而成。幼年成分可能源自对软流圈上升的玄武岩浆岩。这些北北造山带中的早二叠世高钾钙碱性花岗岩可能是在碰撞后的伸展背景下沉积的，表明在CAOB南部有垂直的大陆壳生长，这与CAOB中的大多数花岗岩相同或相似。这项研究为确定南部CAOB的增生后演化提供了新的证据。

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