何家庄岩体的年龄和成因及其对南秦岭早三叠世构造演化的制约

被引：26

作者：

杨朋涛 ^{[1
,2
]}

刘树文 ^{[1
]}

李秋根 ^{[1
]}

王宗起 ^{[3
]}

张帆 ^{[1
]}

王伟 ^{[1
]}

机构：

[1] 北京大学造山带与地壳演化教育部重点实验室

[2] 中国地震局地壳应力研究所地壳动力学重点实验室

[3] 中国地质科学院矿产资源研究所

来源：

中国科学:地球科学 | 2013年 / 43卷 / 11期

关键词：

何家庄花岗闪长岩; 锆石U-Pb同位素定年; 岩石成因; 构造背景; 南秦岭构造演化;

D O I：

暂无

中图分类号：

P548 [区域构造地质学];

学科分类号：

070904 ;

摘要：

何家庄岩体位于勉略带以北的南秦岭构造带北部,主体岩性为花岗闪长岩.LA-ICP-MS锆石U-Pb同位素定年结果揭示这些花岗闪长岩侵位于248 Ma.岩浆锆石的εHf（t）值在4.8～8.8之间变化,Hf亏损地幔模式年龄（TDM）为537～1061 Ma.何家庄岩体花岗闪长岩属于中钾到高钾钙碱性系列,具有与埃达克岩相似的地球化学特征.所有样品均表现为高的SiO2（66.6%70.0%）,Al2O3（15.04%16.10%）,Na2O（3.74%4.33%）含量和Mg#（54.2～61.7）值,高的Sr（627～751 ppm）,Cr（55～373 ppm）和Ni（17.2～182 ppm）含量,低的Y（5.42～8.41 ppm）和Yb（0.59～0.74 ppm）含量,轻重稀土强烈分异(（La/Yb）N=18.9～34.0),但重稀土相对平坦,明显的正Eu异常（δEu=1.10～2.22）,富集大离子亲石元素,亏损Nb,Ta,P和Ti.岩石成因研究表明这些花岗闪长岩形成于岛弧环境下俯冲洋壳残片和沉积物构成的混合源的部分熔融,其熔体受到了地幔楔物质的污染.何家庄岩体年龄及岩石成因证明勉略洋壳俯冲从248 Ma之前就已经开始,并且南秦岭地区在早三叠世仍处于洋壳俯冲动力学背景.

引用

页码：1874 / 1893

页数：20

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