特提斯喜马拉雅带东段列麦白云母花岗岩年代学及成因

发布时间：2019-02-28 14:31

【摘要】：列麦白云母花岗岩位于特提斯喜马拉雅东段,侵位于雅拉香波穹窿边部早古生代浅变质岩中。为揭示其形成时代及成因,本文对其开展LA-ICP-MS锆石U-Pb年代学、Hf同位素及岩石地球化学研究。结果表明列麦白云母花岗岩具有高SiO_2(71.08%～71.49%)、Al_2O_3(15.55%～15.72%)和K_2O(4.32%～4.57%),高的A/CNK比值(1.17～1.21),低的CaO/Na_2O比值(0.22～0.28),属于高钾钙碱性过铝质花岗岩;富集Rb、Th和Hf,亏损Ba、Nb、Sr和Ti,稀土元素呈轻稀土(LREE)富集,重稀土(HREE)相对亏损的向右倾斜的配分模式(LREE/HREE=16.57～17.91),具有弱负Eu异常(δEu=0.78～0.79)。与二云母花岗岩比较,列麦白云母花岗岩具有较高的Rb含量(204.1×10~(-6)～293.8×10~(-6))、较低的Sr(134.6×10~(-6))及显著的重稀土分馏效应。锆石新生边年龄为48.5±1.1 Ma(MSWD=2.1),代表其结晶年龄,该年龄为目前报道的最早年龄,其初始Hf同位素组成ε_(Hf)(t)=-6.4～-2.3,显示物源为壳源性质,二阶段模式年龄介于731～839 Ma之间,表明成岩物质形成于新元古代;核部继承锆石年龄变化在135.7～3339.2 Ma之间,表明其源岩为早白垩世沉积岩,是在印度与欧亚大陆主碰撞阶段,陆-陆碰撞导致地壳缩短加压升温,引起早白垩世沉积岩部分熔融而形成的。
[Abstract]:The Lemaic Muscovite granite is located in the eastern part of the Tethys Himalayas and is located in the early Palaeozoic shallow metamorphic rocks at the edge of the Yalashenbo dome. In order to reveal the age and origin of its formation, the LA-ICP-MS zircon U-Pb chronology, Hf isotopes and petrogeochemistry have been studied in this paper. The results show that the Lemai Muscovite granites have high SiO_2 (71. 49%), Al_2O_3 (15. 55%) and K ~ (2 +) 2O (4. 32% ~ 4. 57%). The high A/CNK ratio (1.17 ~ 1.21) and the low CaO/Na_2O ratio (0.22 ~ 0.28) belong to the high potassium calc-alkaline peraluminous granite; The enrichment of Rb,Th and Hf, deficient Ba,Nb,Sr and Ti, showed light rare earth (LREE) enrichment, while the heavy rare earth (HREE) was relatively deficient in the right-leaning partition model (LREE/HREE=16.57~17.91). There is a weak negative Eu anomaly (未 EU = 0.78? 0.79). Compared with Ermica granite, Lemaibai granite has higher Rb content (204.1 脳 10 ~ (- 6) ~ 293.8 脳 10 ~ (- 6), lower Sr (134.6 脳 10 ~ (- 6) and significant heavy rare earth fractionation effect. The new edge age of zircon is 48.5 卤1.1MPa (MSWD=2.1), which represents the crystallization age, which is the earliest reported age. The initial Hf isotopic composition 蔚 _ (Hf) (t) =-6.4? The two-stage model age is between 731 and 839 Ma, indicating that the diagenetic material was formed in Neoproterozoic. The age of the inherited zircon varies between 135.7 and 3339.2 Ma, indicating that the source rock is an early Cretaceous sedimentary rock, which was caused by the continental-continental collision during the main collision stage between India and Eurasia. Resulting in partial melting of early Cretaceous sedimentary rocks.
【作者单位】：中国地质大学资源学院;江西省地矿局物化探大队;中国地质大学地球科学与资源学院;中国地质大学地质调查研究院;
【基金】：青藏高原矿产调查评价专项项目(编号1212011220664)资助成果
【分类号】：P588.121;P597.3

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