河南新县地区早白垩世花岗岩矿物温压计研究

Research on Thermometers and Barometers of early Cretaceous granite in Xinxian County,Henan Province,China

在野外地质调查、岩相学和岩石化学研究基础上,本文通过新县花岗岩岩基、宝安寨花岗岩体和大银尖花岗岩体的全岩锆饱和温度、斜长石—碱性长石平衡温度和绿泥石蚀变温度的计算,参照前人研究成果,阐述新县地区早白垩世花岗岩形成时的温度、压力和深度以及与成矿的关系等.研究表明,新县花岗岩岩基、宝安寨花岗岩体和大银尖花岗岩体的全岩锆饱和温度分别为759℃、773℃、748℃,代表各自岩体形成时的上限温度;二长石平衡温度分别为358℃、454℃、467℃左右,代表各自岩体形成时的下限温度.黑云母全铝压力计计算所得成岩压力分别为1.15kbar^2.01kbar、0.86kbar^2.31kbar以及1.46kbar^2.54kbar,对应各自成岩深度分别为4.3km^7.6km、3.3km^8.7km、5.5km^9.6km,表明岩体侵位于地壳上部.绿泥石主要为斜绿泥石,形成于还原环境,蚀变温度分别为285℃、313℃和303℃,与成矿流体沸腾作用时温度大致相近.

Based on field geological investigation, petrography and chemistry, this paper calculates the whole rock Zr saturation temperature, two-feldspar equilibrium temperature and the alteration temperature of chlorite for Xinxian granitic batholith, Bao’anzhai granitic stock and Dayinjian granitic stock. With reference to previous research, we elaborate the rock forming temperature, pressure, depth and the relationship with mineralization of early Cretaceous granites in Xinxian region. The study shows that the whole rock Zr saturation temperatures of Xinxian granitic batholith, Bao’anzhai and Dayinjian granitic stocks are 759℃, 773℃ and 748℃ respectively, representing the maximum temperature of the rock formation, while two-feldspar equilibrium temperatures are about 358℃, 454℃ and 467℃ respectively, representing the minimum temperature of the rock formation. Biotite whole aluminum barometer shows that the rock forming depths are 4.3 km-7.6 km, 3.3 km-8.7 km and 5.5 km-9.6 km respectively, corresponding to the pressures as 1.15 kbar-2.01 kbar, 0.86 kbar-2.31 kbar and 1.46 kbar-2.54 kbar respectively, indicating these plutons emplacing in the upper crust. Chlorite mainly belongs to clinochlore forming in the reducing environment with the formation temperatures as 285℃, 290℃ and 309℃ respectively, which are roughly similar with the ore-forming fluid boiling temperature.