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张建岭,许德如,于得水,王智琳,叶挺威,于亮亮,朱昱桦. 2018. 赣中山庄二长花岗岩的成因与构造背景:岩石学、地球化学及锆石U-Pb年代学证据. 岩石学报, 34(6): 1641-1656
赣中山庄二长花岗岩的成因与构造背景:岩石学、地球化学及锆石U-Pb年代学证据
作者单位E-mail
张建岭 中国科学院广州地球化学研究所矿物学与成矿学重点实验室, 广州 510640
中国科学院大学, 北京 100049 
 
许德如 中国科学院广州地球化学研究所矿物学与成矿学重点实验室, 广州 510640
东华理工大学地球科学学院, 南昌 330013 
xuderu@gig.ac.cn 
于得水 中国科学院广州地球化学研究所矿物学与成矿学重点实验室, 广州 510640
中国科学院大学, 北京 100049 
 
王智琳 中南大学地球科学与信息物理学院, 长沙 410083  
叶挺威 中国科学院广州地球化学研究所矿物学与成矿学重点实验室, 广州 510640
中国科学院大学, 北京 100049 
 
于亮亮 中国科学院广州地球化学研究所矿物学与成矿学重点实验室, 广州 510640
中国科学院大学, 北京 100049 
 
朱昱桦 中国科学院广州地球化学研究所矿物学与成矿学重点实验室, 广州 510640
中国科学院大学, 北京 100049 
 
基金项目:本文受国家自然科学基金项目(41472171)和国家重点研发计划项目(2016YFC0600401)联合资助.
摘要:
      赣中山庄花岗岩岩体位于钦杭成矿带的南侧,岩性上包括二长花岗岩和花岗闪长岩。本文对岩体北部的二长花岗岩开展了年代学、地球化学及同位素研究以约束该岩体的形成时代、岩石成因及成岩构造背景。锆石CL图像、Th/U比值,以及(Sm/La)N-La和Ce/Ce*-(Sm/La)N图解均表明,二长花岗岩所有锆石晶体为岩浆成因;其中第一组锆石加权平均年龄为420~419Ma,代表了岩浆结晶年龄。该花岗岩SiO2含量为71.48%~66.20%、K2O/Na2O值为1.24~0.99、A/CNK>1.1;结合白云母和石榴石的出现、ACF图解、Rb-Th、Rb-Y的负相关性,山庄二长花岗岩属高钾钙碱性强过铝质S型花岗岩。同时,该岩石亏损大离子亲石元素Ba和Sr以及高场强元素Nb和Ta,说明系壳源物质部分熔融的产物。CaO/Na2O值(0.14~0.07)、Rb/Sr值(8.27~3.83)、Rb/Ba值(1.48~0.82)、FeOT+MgO+TiO2含量(2.4~1.8)和二阶段Nd模式年龄(t2DM=2031~1971Ma)进一步说明二长花岗岩的源岩是古元古代的富粘土的泥质岩。锆石的饱和温度和Ti温度计计算结果表明二长花岗岩岩浆形成温度为722~720℃,黑云母的全铝温度计则反映其形成压力为3.21~2.71kbar。结合花岗岩构造环境判别图以及华南大地构造演化特征,山庄花岗岩岩体可能是在后碰撞环境下由古元古代富粘土泥质岩于低温低压条件下部分融熔的结果。
英文摘要:
      This paper presents a systemic study on geochronology, geochemistry and Sr-Nd isotopes of the northern monzogranite from Shanzhuang granitic pluton located on the southern part of the Qinhang Metallogenic Belt in central Jiangxi Province which comprises monzogranite and granodiorite to constrain its emplacement age, petrogenesis and tectonic setting. All zircons from the monzogranite are confirmed to be of magmatic origin by CL imaging, Th/U ratio and diagrams of (Sm/La)N-La and Ce/Ce*-(Sm/La)N and are divided into three groups. The weighted mean age (420~419Ma) of the first group is interpreted as crystallization age of the monzogranite. The Shanzhuang monzogranite, which has SiO2 content of 71.48%~66.20%, K2O/Na2O ratio of 1.24~0.99 and A/CNK ratio of >1.1, with the emergences of muscovite and garnet as well as ACF diagram and negative correlations of Rb with Th and Y, belongs to high K calc-alkaline, strongly peraluminous S-type granite. Meanwhile, this type rock defined by a depletion in large ion lithophile elements Ba and Sr and high field strength elements Nb and Ta is interpreted as a product of partial melting of the crust-derived materials. The ratios of CaO/Na2O (0.14~0.07), Rb/Sr (8.27~3.83) and Rb/Ba (1.48~0.82), the content of FeOT+MgO+TiO2 (2.4~1.8) and the t2DM ages (2031~1971Ma) together suggest that the protolith of the monzogranite is Paleoproterozoic clay-rich argillaceous rocks. Moreover, the monzogranite is likely formed at a temperature condition (722~720℃) constrained by saturation-and Ti temperatures of zircon, and a pressure condition of 2.71~3.21kbar constrained by the Ti-in-biotite geothermometer. Combined with the Paleozoic tectonic development of South China, the diagram of Rb-(Y+Nb) shows that the geological setting of Shanzhuang granitic pluton is post-collision. In summary, the Shanzhuang pluton was formed by partial melting of Paleoproterozoic clay-rich argillaceous rocks at a low temperature and a low pressure condition under post-collisional setting.
关键词:山庄花岗岩  锆石U-Pb年龄  地球化学和Sr-Nd同位素  后碰撞  江西中部
投稿时间:2017-05-19  修订日期:2018-05-19
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