Zircon SHRIMP U-Pb ages and trace element geochemistry of the Kuhai gabbro and the Dur''''ngoi diorite in the southern east Kunlun tectonic belt, Qinghai, Western China and their geological implications     

LI WangYe  LI ShuGuang  GUO AnLin  SUN YanGui  ZHANG GuoWei 《中国科学D辑(英文版)》2007,50(Z2):331-338

Timing of the intermediate-basic igneous rocks developed in the area of Kuhai-A'nyêmaqên along the southern east Kunlun tectonic belt is a controversial issue. This paper presents new zircon SHRIMP U-Pb dating data for igneous zircons from the Kuhai gabbro and the Dur'ngoi diorite in the Kuhai-A'nyemaqen tectonic belt, which are 555±9 Ma and 493±6 Ma, respectively. The trace element geochemical features of the Kuhai gabbro and the Dur'ngoi diorite are similar to those of ocean island basalts (OIB) and island arc basalts (IAB), respectively. Thus, the Kuhai gabbro with the age of 555±9 Ma and OIB geochemical features is similar to the Yushigou oceanic ophiolite in the North Qilian orogen, whereas the Dur'ngoi diorite with the age of 493±6 Ma and IAB geochemical features is similar to the island arc volcanic rocks developed in the north Qaidam. The Late Neoproterozoic to Early Ordovician ophiolite complex in the area of Kuhai-A'nyêmaqên suggests that the southern margin of the "Qilian-Qaidam-Kunlun" archipelagic ocean in this period was located in the southern east Kunlun tectonic belt. Therefore, the southern east Kunlun tectonic belt in the early Paleozoic is not comparable to the Mianlüe tectonic belt in the Qinling orogenic belt.  相似文献   

镁同位素地球化学研究新进展及其应用   总被引：7，自引：3，他引：4  

柯珊  刘盛遨  李王晔  杨蔚  滕方振 《岩石学报》2011,27(2):383-397

作为一种新兴的地质示踪剂,Mg同位素正受到国际地学界日益广泛的关注。Mg同位素地球化学研究已取得了巨大的进展,近期研究工作主要包括两个方面。首先,调查了地球各主要储库和陨石的Mg同位素组成特征,结果表明陨石和地球地幔具有均一并且相似的Mg同位素组成,平均δ²⁶Mg值分别为-0.28±0.06‰和-0.25±0.07‰;相反,上地壳和水圈的Mg同位素组成很不均一,δ²⁶Mg值变化范围分别为-4.84‰~+0.92‰和-2.93‰~+1.13‰。其次,对一些地质和物理化学过程中Mg同位素的分馏行为进行研究,结果表明:(1)地表风化作用可以造成大的Mg同位素分馏,导致重Mg同位素残留在风化产物中而轻Mg同位素进入水圈;(2)岩浆分异过程中Mg同位素平衡分馏很小;(3)高温化学扩散和热扩散过程中Mg同位素会发生显著的动力学分馏。基于这些研究成果,Mg同位素体系已经被初步应用于示踪早期地球形成和壳内物质再循环等过程,并有望在不久的将来应用于示踪大陆地壳的化学演化和地质温度计等研究领域。  相似文献   

西秦岭关子镇蛇绿混杂岩的地球化学和锆石SHRIMP U-Pb年龄   总被引：3，自引：2，他引：3  

李王晔李曙光  裴先治张国伟 《岩石学报》2007,23(11):2836-2844

西秦岭沿天水武山断裂带产出的关子镇蛇绿混杂岩由变玄武岩、变中-基性深成岩浆岩以及少量蛇纹岩组成。变玄武岩具有平坦或轻稀土略亏损的稀土配分型式((La/Yb)_N=0.63～1.24),且不存在Nb、Ta和Ti的负异常,表明它们形成于洋中脊环境。变中-基性深成岩浆岩包含两种类型:类型Ⅰ显示轻稀土富集((La/Yb)_N>2.2)、具有显著Nb负异常((La/Nb)_N>2.4)的特征,类似于岛弧火山岩;类型Ⅱ显示轻稀土亏损到略富集((La/Yb)_N=0.44～1.38)、无显著Nb负异常((La/Nb)_N<1.5),这些特征与上述变玄武岩类似,表明它们也是关子镇蛇绿岩的组成部分。蛇绿岩中辉长岩和闪长岩(该闪长岩属"大洋斜长花岗岩类")样品的锆石SHRIMP U-Pb年龄分别为534±9Ma和517±8Ma,这反映关子镇蛇绿岩可能为早-中寒武世古洋壳残片。由于西秦岭的天水武山断裂带是东秦岭商丹断裂带的西延并共同被认为是华北和华南陆块之间的主缝合线,上述年龄对理解该带及古秦岭洋的演化提供了重要制约。  相似文献   

Zircon SHRIMP U-Pb ages and trace element geochemistry of the Kuhai gabbro and the Dur’ngoi diorite in the southern east Kunlun tectonic belt,Qinghai, Western China and their geological implications     

Li  WangYe  Li  ShuGuang  Guo  AnLin  Sun  YanGui  Zhang  GuoWei 《中国科学:地球科学(英文版)》2007,50(2):331-338

Timing of the intermediate-basic igneous rocks developed in the area of Kuhai-A’nyêmaqên along the southern east Kunlun tectonic belt is a controversial issue. This paper presents new zircon SHRIMP U-Pb dating data for igneous zircons from the Kuhai gabbro and the Dur’ngoi diorite in the Kuhai-A’nyemaqen tectonic belt, which are 555±9 Ma and 493±6 Ma, respectively. The trace element geochemical features of the Kuhai gabbro and the Dur’ngoi diorite are similar to those of ocean island basalts (OIB) and island arc basalts (IAB), respectively. Thus, the Kuhai gabbro with the age of 555±9 Ma and OIB geochemical features is similar to the Yushigou oceanic ophiolite in the North Qilian orogen, whereas the Dur’ngoi diorite with the age of 493±6 Ma and IAB geochemical features is similar to the island arc volcanic rocks developed in the north Qaidam. The Late Neoproterozoic to Early Ordovician ophiolite complex in the area of Kuhai-A’nyêmaqên suggests that the southern margin of the “Qilian-Qaidam-Kunlun” archipelagic ocean in this period was located in the southern east Kunlun tectonic belt. Therefore, the southern east Kunlun tectonic belt in the early Paleozoic is not comparable to the Mianlüe tectonic belt in the Qinling orogenic belt.

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