江西九瑞矿集区成矿与未成矿中酸性侵入岩年代学、岩石化学、矿物化学特征的异同及地质意义  

Geochronology,geochemistry and mineralogy of ore-bearing and ore-barren intermediate-acid intrusive rocks from the Jiurui ore district,Jiangxi Province and their geological implications

作　　者：徐耀明[1] 蒋少涌[1,2,3] 朱志勇[1] 周巍[1] 孔凡斌[1,4] 孙明志[1] 熊永根[1] 

机构地区：[1]内生金属矿床成矿机制研究国家重点实验室南京大学地球科学与工程学院,南京210093 [2]地质过程与矿产资源国家重点实验室中国地质大学,武汉430074 [3]中国地质大学资源学院和紧缺战略矿产资源协同创新中心,武汉430074 [4]江西地质矿产勘查开发局赣西北大队,九江332000

出　　处：《岩石学报》2013年第12期4291-4310,共20页Acta Petrologica Sinica

基　　金：科技部973项目(2012CB416706);“十二五”国家科技支撑计划(2011BAB04B03);国家自然科学基金项目(41072055)联合资助

摘　　要：江西九瑞矿集区主要发育有斑岩型、矽卡岩型及块状硫化物型三种类型的铜多金属矿床，其中斑岩型与矽卡岩型为典型的岩浆热液矿床，块状硫化物型矿床产在五通组砂岩与黄龙组白云岩界面之中，但多数也均位于侵入体附近，通常认为岩浆热液对层状黄铁矿体的叠加作用对其成矿起了重要作用。区内同时发育有大量与成矿岩体岩性相似的未成矿侵入岩，长期以来，一直未能找出成矿侵入岩的判别标志和侵入岩成矿与否的原因。本文对区内岩性为花岗闪长斑岩、石英闪长玢岩的成矿与未成矿侵入岩进行了锆石U-Pb定年、岩石主量元素分析以及造岩矿物电子探针测试工作，结果显示，九瑞地区岩浆活动的时代相对集中，成矿侵入岩的年龄分布于138.21.8Ma至148.01.0Ma之间，未成矿侵入岩的年龄分布于139.01.3Ma至149.63.0Ma之间，成矿与未成矿侵入岩的侵位时代基本相同，年龄在误差范围内一致。二者的SiO2以及其它9种主量元素含量的变化范围都非常接近，或有很大重叠，表明成矿与未成矿侵入岩的主要岩石化学成分基本相同。通过造岩矿物成份计算了岩浆开始固结的温度和侵位压力，成矿侵入岩的平均温度769℃与未成矿侵入岩的平均温度723℃在误差范围内大体一致，但成矿侵入岩的温度变化范围（580~915℃）明显大于未成矿侵入岩（656~796℃）。侵位压力方面，未成矿侵入岩的压力值（平均5.7kbar）显著大于成矿侵入岩（平均1.4kbar）。因此我们认为，成矿与未成矿侵入岩相比，前者经历了更为显著的减压过程，该过程也许对形成岩浆热液矿床非常重要，可能是产生独立热液相的一个主要途径，并且能够在岩体内及围岩中造成大量裂隙，为热液循环提供通道。但是，数据同时显示，并非经历了显著减压过程的侵入岩都能够成矿，最终成矿与否是The major types of copper polymetallic ore deposit in Jiurui ore district include porphyry, skarn and massive sulfide types. Porphyry and skarn types are typical magmatic-hydrothermal deposits, and the massive sulfide deposits of Jiurui area occurred along the strata near the sandstone and dolomite boundary but also located near intrusive rocks, which shows that magmatic-hydrothermal fluids may have also played a crucial role in the mineralization processes. In Jiurui area, petrographic characters of ore-barren intrusive rocks are almost the same as ore-bearing samples, and parameters to identify between ore-bearing and ore-barren intrusive rocks as well as how these parameters affect mineralization are still unknown. In order to solve above problems, a detailed study on geochronology, major elemental geochemistry and mineral chemistry was performed for the ore-bearing and ore-barren quartz diorite-porphyrite and granodiorite porphyry from the Jiurui ore district, Jiangxi Province. Zircon U-Pb dating results demonstrate that extensive magmatism was coeval and intensive in this area, with emplacement ages of 138.21.8Ma to 148.01.0Ma for the ore-bearing intrusive rocks, and 139.01.3Ma to 149.63.0Ma for the ore-barren intrusive rocks, which are consistent within the error range with each other. The variation ranges of SiO2 and other 9 major oxides are quite similar between ore-bearing and ore-barren intrusive rocks. The average temperatures of ore-bearing and ore-barren intrusive rocks are 769℃ and 723℃ respectively, which are also not much difference. However, the variation range of the ore-bearing intrusive rocks （580~915℃） is obviously greater than the ore-barren ones （656~796℃）. It is remarkable that the average pressure of ore-barren intrusive rocks （5.7kbar） is evidently greater than the ore-bearing samples （1.4kbar）. Therefore, the ore-bearing intrusive rocks from the Jiurui area should have experienced a more distinctive pressure decreasing process, which is quite important to form ma

关 键 词：锆石U-Pb定年 主量元素 矿物化学 温度 压力 氧逸度 中酸性侵入岩 九瑞矿集区 

分 类 号：P588.12[天文地球—岩石学]