藏南拿日雍错片麻岩穹窿中新世淡色花岗岩的形成过程:变泥质岩部分熔融与分离结晶作用

发布时间：2018-04-22 18:14

本文选题：藏南 + 特提斯喜马拉雅　；参考：《岩石学报》2017年08期

【摘要】：拿日雍错片麻岩穹窿位于特提斯喜马拉雅带的东部,穹窿边部淡色花岗岩脉形成于21.8±0.3Ma,穹窿核部主体淡色花岗岩的结晶年龄为20.1±0.1Ma,其中1件样品记录了~17.3Ma热液蚀变事件。大部分淡色花岗岩具有以下特征:(1)较高的Si O2(72.9%),Al2O3(14.7%)和A/CNK(1.1),较低的Fe O、Mg O、Mn O和Ti O2;(2)高度变化的大离子亲石元素(如Rb、Sr、Ba)和高场强元素(如Nb、Ta、Hf、Th)和Rb/Sr、Nb/Ta、Zr/Hf比值;(3)富集轻稀土元素,亏损重稀土元素,Eu和Nd都显示负异常(Eu/Eu*0.7,Nd/Nd*=0.5~0.8);(4)Sr同位素比值变化范围较大(87Sr/86Sr(t)=0.7132~0.7330),但Nd同位素比值一致(εNd(t)=-12.4~-10.9)。这些特征表明:拿日雍错淡色花岗岩形成于20Ma,是变泥质岩部分熔融作用的产物,经历了不同程度的斜长石、锆石、独居石、磷灰石、富Ti矿物等的分离结晶作用。
[Abstract]:The dome gneiss dome is located in the eastern part of the Himalaya belt of Tethys. The pale granite veins in the dome are 21.8 + 0.3Ma, and the crystalline age of the main body light granite is 20.1 + 0.1Ma. 1 of them recorded the ~17.3Ma hydrothermal alteration events. Most of the light color granites have the following characteristics: (1) higher Si O2 (72.9%). Al2O3 (14.7%) and A/CNK (1.1), lower Fe O, Mg O, Mn O and Ti O2; (2) high variation of large ionic stone elements (such as Rb, Sr, etc.) and high field strength elements; (3) enrichment of light rare earth elements, loss of heavy rare earth elements, both of which show negative anomalies; (4) variation of isotopic ratios. The range is larger (87Sr/86Sr (T) =0.7132~0.7330), but the ratio of Nd isotopes is consistent (epsilon Nd (T) =-12.4~-10.9). These characteristics indicate that the zonyazin granite is formed in 20Ma and is a product of partial melting of metamorphic rocks, and has experienced the separation and crystallization of different degrees of plagioclase, zirconium, monazite, apatite, and rich Ti minerals.

【作者单位】：中国地质科学院地质研究所;中国地质科学院矿产资源研究所;
【基金】：国家重点研发计划(2016YFC0600304) 国家自然科学基金项目(41425010、41503023、41273034) 中国地质科学院地质研究所基本科研业务费项目(J1516) 中国地质调查局地质调查项目(12120115027101)联合资助
【分类号】：P588.121;P588.3

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