摘要
柴达木盆地北缘(以下简称柴北缘)—东昆仑地区已经勘查发现了一批造山型金矿,它们是加里东和晚华力西—印支复合造山作用的产物。通过柴北缘—东昆仑地区12处造山型金矿中流体包裹体研究发现,该区造山型金矿中发育两种不同的成矿流体:低盐度的H2O-CO2-NaCl-CH4流体和低盐度的H2O-CO2-NaCl±CH4。前者的XCH4、XCO2和XH2O分别为0.14～0.34(平均值0.24)、0.11～0.59(平均值0.34)和0.64～0.31(平均值0.42),温度变化为180～270℃,压力为180～560Mpa,是晚加里东期碰撞造山作用的产物,主要沿加里东碰撞造山带边界的上地壳底部-中地壳上部的塑性变形带大规模流动,并在本区形成了广泛的金矿化;后者的XCH4、XCO2和XH2O分别为0～0.12(平均值0.06)、0.18～0.25(平均值0.21)和0.79～0.69(平均值0.73),温度变化为280～449℃(主要在280～360℃),压力为80～230Mpa,主要与晚华力西—印支期碰撞造山作用有关,其中不少矿床还受侵入岩浆作用的影响,其沿晚华力西—印支期碰撞造山带边界的上地壳大规模流动,导致了本区造山型金矿的最终定位。上述两期成矿流体的盐度相差不大,总体变化在1.4%～11.4%(NaCl)(大部分集中于2.7%～9.1%)。压力-深度换算结果显示,本区晚华力西—印支期碰撞造山作用表现出地壳强烈隆升过程,其最大隆升幅度达12km。这说明该区大规模的造山型金成矿作用发生在地壳隆升的背景之下。
More than 20 orogenic gold mineral occurrences have been discovered and explored in the northern Qaidam margin-East Kunlun region. They are the product of the late Caledonian and late Variscan-Indosinian multiple collisional orogeny. Based on a study of fluid inclusions in 12 gold deposits in the region, two kinds of ore-forming fluids are recognized in these orogenic gold deposits： low-salinity H2O-CO2-NaCl-CH4 fluids and low-salinity H2O-CO2-NaCl±CH4 fluids. The former, whose XCH4, XCO2 and X^H2O values are 0.14-0.34 （mean 0.24）, 0.11-0.59 （mean 0.34） and 0.64-0.31 （mean 0.42） respectively, temperatures range from180 to 270℃ and pressures range from 180 to 560 MPa, are the product of late Caledonian collisional orogeny and mainly flowed along the ductile deformation zone between the base of the upper crust and the upper part of the middle crust below the boundary of the Caledonian collisional orogenic belt and formed extensive gold mineralizations in the region. For the latter, the values of XCH4, XCO2 and XH2O are 0-0.12 （mean 0.06）, 0.18-0.25 （mean 0.21） and 0.79-0.69 （mean 0.73）, the temperatures range from 280 to 449℃ （mostly 280-360℃） and the pressures range from 80 to 230 MPa. They were mainly related to late Variscan-Indosinian collisional orogeny and influenced by magmatic intrusion in some deposits. The fluids flowed extensively along the upper crust below the boundary of the late Variscan-Indosinian collisional orogenic belt, thus resulting in the final location of orogenic gold deposits in the region. The salinities of the two kinds of fluids are approximately consistent, generally varying from 1.4 to 11.4 wt% NaC1 equiv and clustering at 2.7-9.1 wt% NaClequiv. The results of pressure-depth conversion of the ore-forming fluids indicate a process of strong crustal uplift during the late Variscan-Indosinian collisional orogeny in the region, with the maximum uphft magnitude up to 12 kin. This shows that the orogenic gold mineralizations in the region took place in a background of crustal uphft.
出处
《中国地质》
CAS
CSCD
2007年第5期843-854,共12页
Geology in China
基金
国家自然科学基金面上项目(40372051)
十一五国家科技支撑计划项目(2006BAB01A06)共同资助
关键词
流体包裹体
造山型金矿
青海柴北缘-东昆仑
fluid inclusion
orogenic gold deposit
northern Qaidam margin-East Kunlun region
Qinghai
