投稿时间：2021-05-12
修订日期：2022-03-03
网络发布日期：2023-01-07
中文摘要:东秦岭构造带发育大量古生代花岗岩和赋存稀有金属以及铀矿床（化）的花岗伟晶岩，但二者的成因联系尚不清楚。因此，文章统计了花岗岩和花岗伟晶岩的年龄，并对比了二者全岩和矿物的元素和同位素组成，以此探讨二者之间的成因联系。年龄统计结果表明花岗岩形成于3期岩浆活动：第一期（490~500 Ma）形成了区域上最大的漂池S型花岗岩体；第二期（435~460 Ma）峰期约为450 Ma，形成了东秦岭广泛发育的二长花岗岩，为区域上最大的灰池子I型花岗岩体的主体岩性；第三期（约420 Ma）形成了分布范围和规模均较小的正长花岗岩。赋存稀有金属矿床（化）的花岗伟晶岩形成时代为380~440 Ma，而赋存铀矿床（化）的黑云母花岗伟晶岩形成时代约为420 Ma，与第三期正长花岗岩的形成时代相同。稀有金属矿化伟晶岩与漂池岩体的锆石Lu-Hf同位素组成相似，说明二者均为秦岭群部分熔融的产物，但并不存在演化关系。另一方面，相似的全岩Sr-Nd和锆石Lu-Hf同位素组成表明正长花岗岩与黑云母花岗伟晶岩具有相同的源区，而且二者具有相似的全岩微量元素组成和黑云母离子替代方式，暗示它们存在演化关系。正长花岗岩母岩浆的温度比黑云母花岗伟晶岩母岩浆高100℃，而且从正长花岗岩到黑云母花岗伟晶岩锆石中U含量升高而Ti和重稀土元素（HREE）含量降低，说明黑云母花岗伟晶岩是同时期正长花岗岩分异晚期的产物。
Abstract:Numerous Paleozoic granite plutons and rare-metal- and uranium-mineralized granitic pegmatites occur in the East Qinling tectonic belt, but their genetic relationship is still unclear. In this study, we compiled the ages and compared the elemental and isotopic compositions of whole-rock and mineral of granites and granitic pegmatites from previous studies and our unpublished data, in order to investigate their genetic relationship. The age compilation suggests that the granite plutons formed in three stages of magmatism. The first stage lasted during 490~500 Ma with the formation of the largest S-type Piaochi pluton in this region, the second stage occurred during 435~460 Ma with a summit at ~450 Ma, forming the widely distributed monzogranite which is the main body of the largest I-type Huichizi pluton in this region, and the third stage occurred at ca. 420 Ma with the formation of a series of small-scale syenogranite stocks. The U-mineralized biotite granitic pegmatites were formed around 420 Ma, similar to the syenogranite stocks. The granitic pegmatites associated with rare-metal deposits were formed during 380~440 Ma. Rare-metal mineralized pegmatites have similar Lu-Hf isotopic compositions to the Piaochi pluton, indicating that they may be derived from the partial melting of the Qinling Formation, but the distinct formation ages rule out their relationship during evolution after emplacement. On the other hand, similar whole-rock Sr-Nd and in-situ Lu-Hf isotopic compositions suggest that the syenogranite and biotite granitic pegmatites were derived from the same source region. In addition, the similar whole-rock trace elements as well as the same manner of ion substitution for biotite from the syenogranite and biotite granitic pegmatites, suggest that they may have a genetic link. The parental magma of the biotite granitic pegmatites is 100℃ lower than that of the syenogranite. Furthermore, the increase of U concentration and decrease of Ti and heavy rare earth elements (HREE) of zircon from syenogranite to biotite granitic pegmatite, indicat that the biotite granitic pegmatites were formed in the late stage of crystallization of syenogranite.
文章编号：
中图分类号：
文献标志码：
基金项目:本文得到国家重点研发计划（编号：2019YFC0605202）、陕西省自然科学基础研究计划项目（编号：2018JM4009和2020JM-215）和中央高校基本科研业务费专项资金（编号：300102271208）共同资助
引用文本：
王梦玺,郭腾龙,凤永刚,梁婷,周义,孙小筠.2022.东秦岭构造带古生代花岗岩与赋矿花岗伟晶岩的成因联系[J].矿床地质,41(6):1124~1141WANG MengXi,GUO TengLong,FENG YongGang,LIANG Ting,ZHOU Yi,SUN XiaoYun.2022.Genetic link of Paleozoic granites and mineralized granitic pegmatites in East Qinling tectonic belt[J].Mineral Deposits41(6):1124~1141
图/表
