湖南塔山岩体岩石学、地球化学、U-Pb年代学特征及其形成构造背景

发布时间：2018-11-14 20:40

【摘要】：塔山岩体处于阳明山-塔山-大义山东西向构造—岩浆带中部,是南岭成矿带的重要组成部分,出露面积约200km~2。该岩体为岩浆多期次侵入形成的中深成复式岩体,整体剥蚀程度较低,可划分为5个侵入期次,从早期到晚期,各侵入期次岩体的岩石学及重矿物特征呈现出规律性变化。塔山岩体富硅、富铝,属铝过饱和钙碱性酸性花岗岩类,其Ba、Nb、Sr、P、Ti显著亏损,并具有明显的铕负异常及轻稀土元素分馏明显而重稀土元素分馏不明显的特征。塔山岩体第2侵入期次和第3侵入期次岩体的SHRIMP锆石U-Pb同位素年龄分别为(218±3)Ma和(215±3)Ma,属于晚三叠世。岩石学、地球化学特征表明塔山岩体为地壳部分熔融形成的S型花岗岩,源岩主要为上地壳泥质岩石。微量元素和稀土元素特征显示岩浆形成与板内挤压造山运动停止时挤压剪切应力释放导致的压力下降、岩石升温、熔点降低有关,岩浆成岩过程既受部分熔融也受分离结晶作用控制。地球化学判别显示塔山岩体为印支晚期伸展构造环境下形成的后碰撞花岗岩。
[Abstract]:The Tashan rock body is located in the middle of Yangmingshan-Tashan-Dayishan east-west tectonic-magmatic belt, which is an important part of Nanling metallogenic belt, with an exposed area of about 200 km2. The rock mass is a medium-deep complex formed by magmatic multi-stage intrusion, and the whole denudation degree is relatively low, which can be divided into five intrusive stages. From early to late period, the petrological and heavy mineral characteristics of each intrusive stage show regular changes. The Tashan rock body is rich in silicon and aluminum. It is a supersaturated calc-alkaline acidic granite with obvious Ba,Nb,Sr,P,Ti depletion and obvious negative EU anomalies and obvious fractionation of light rare earth elements but not heavy rare earth elements. The SHRIMP zircon U-Pb isotopic ages of the second and third intrusions are (218 卤3) Ma and (215 卤3) Ma, respectively, belonging to the late Triassic. The petrological and geochemical characteristics indicate that the Tashan rock body is S-type granite formed by partial melting of the crust and the source rock is mainly shaly rock of the upper crust. The characteristics of trace elements and rare earth elements show that magma formation is related to the decrease of pressure caused by the release of compressive shear stress, the increase of rock temperature and the decrease of melting point when the intraplate extrusion orogeny stops. The process of magmatic diagenesis is controlled by both partial melting and separation crystallization. Geochemical discrimination shows that the Tashan rock body is a post-collision granite formed in the late Indosinian extensional tectonic environment.
【作者单位】：湖南省地质调查院;
【基金】：中国地质调查局地质调查子项目“湖南上堡地区矿产远景调查”(1212011120809);“湖南苗儿山地区矿产地质调查”(12120114024201)及其所属的二级项目“南岭成矿带地质矿产调查”(121201009000150002)
【分类号】：P588.12;P59

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