松潘造山带金川地区观音桥晚三叠世二云母花岗岩的成因及其地质意义

发布时间：2018-07-05 14:26

本文选题：松潘造山带 + 二云母花岗岩　；参考：《地质论评》2017年06期

【摘要】：松潘造山带内发育大量印支期花岗岩,这些花岗岩类对于该地区岩浆活动、基底性质和构造演化的研究有着重要的意义。金川地区观音桥二云母花岗岩位于松潘造山带东部,属于晚三叠世花岗岩。岩石具有高硅(SiO_2=72.08%~73.95%)、富碱(K_2O=4.44%~5.84%、Na_2O=3.29%~3.93%)的特征,其A/CNK值为1.08~1.22,属于过铝质高钾钙碱性S型花岗岩类。岩石富集大离子亲石元素,亏损部分高场强元素,具有明显的Eu负异常(δEu=0.26~0.38)。观音桥二云母花岗岩的ε_(Nd)(t)=-7.9~-10.1(平均为-8.9)不高,Nd同位素二阶段模式年龄T_(2DM)值为1.42~1.57 Ga,显示源岩应该为中元古代地壳岩石。岩石高的Rb/Sr值和低的CaO/Na_2O值、较低的Al_2O_3/TiO_2值和低的Rb/Ba值,表明其起源于泥质源岩的部分熔融。综合地球化学、同位素特征和区域地质资料,笔者等认为金川地区观音桥二云母花岗岩是在松潘造山带挤压背景下,由中—上地壳泥质源岩发生部分熔融而形成。
[Abstract]:A large number of Indosinian granites have been developed in the Songpan orogenic belt. These granites are of great significance for the study of magmatic activity, basement properties and tectonic evolution in the area. Guanyinqiao mica granite in Jinchuan area is located in the east of Songpan orogenic belt and belongs to late Triassic granites. The rocks are characterized by high silicon (Sio _ 2 / 72.08) and alkali-rich (K _ 2O _ 4 ~ (4.44) ~ 5.84 ~ 5.84 ~ (3.29) ~ 3.93%), and their A / C _ (K _ (K) is 1.08 ~ 1.22, which belongs to the peraluminous high-potassium calc-alkaline S-type granites. The rocks are rich in large ion lithophile elements and are depleted of some elements with high field strength and have obvious negative EU anomalies (未 EU ~ (2 +) 0.26 ~ (0.38). In the Guanyinqiao mica granite, 蔚 _ (ND) (t) -7.9 ~ (-10.1) (mean -8.9) is not high, and the T2DM value of the two-stage model is 1.42n ~ (1.57) Ga, indicating that the source rocks should be Mesoproterozoic crustal rocks. The high RB / Sr value, the low Cao / Na _ 2O value, the lower Al _ 2O _ 3 / TIO _ 2 value and the low RB / Ba value indicate that the rocks originated from the partial melting of the muddy source rocks. Synthesizing geochemistry, isotopic characteristics and regional geological data, the authors think that the Guanyinqiao mica granite in Jinchuan area was formed by partial melting of mudstone source rocks in the middle and upper crust under the compressional background of Songpan orogenic belt.
【作者单位】：西北大学大陆动力学国家重点实验室/地质学系;
【基金】：国家自然科学基金委创新群体项目(批准号:41421002) 国家自然科学基金资助项目(批准号:41372067,41102037) 全国优秀博士论文作者专项基金资助项目(编号:201324) 陕西省青年科技新星项目的成果~~
【分类号】：P588.121

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