摘要
内蒙古白乃庙铜金钼矿床位于华北板块北缘的中亚造山带的温都尔庙加里东期增生带内,其成矿时间、成因类型和构造环境一直存在分歧。为确定成矿时间,作者运用高精度单颗粒激光熔融氩氩法对含矿石英脉中的黑云母和白云母矿物进行了年龄测定。获得黑云母样品22点^(40)Ar/^(39)Ar等时线年龄为396±2 Ma(MSWD=20),白云母样品23点^(40)Ar/^(39)Ar等时线年龄为358±2 Ma(MSWD=11),确证矿床形成于泥盆纪。矿区斑岩等岩浆岩类侵位年龄为428～466 Ma,早于成矿年龄至少40 Ma;赋矿地层白乃庙群形成于1130Ma左右,早于成矿时间约700Ma。如此大的年龄差表明白乃庙矿床不是斑岩型或海底喷流沉积型矿床,而是通过矿床地质和流体包裹体研究所确定的造山型铜金矿床。白乃庙矿床的成矿年龄与赋矿地层白乃庙群的峰期变质作用年龄(384.5±6Ma)基本一致,也与晚志留世-泥盆纪时温都尔庙增生岩浆弧与华北克拉通北缘的碰撞拼贴时间吻合,因此认为白乃庙铜金矿床形成于碰撞造山体制,是世界首例造山型铜矿床。
The Bainaimiao Cu-Au-Mo deposit, Inner Mongolia, is located at the Ondor Sum Caledonian accretionary belt, eastern Central Asian Orogenic Belt. Its metallogenic type, time and tectonic setting have been debated for a long time. To time the mineralization, the authors dated grains of biotites and muscovites separated from Au-Cu-bearing quartz-vein, using high-resolution single-grain laser-ablation ^40 Ar/^39 Ar method. 22 analyses of biotites yielded a ^40 Ar/^39 Ar isochron age of 396 ± 2 Ma （MSWD = 20）, and 23 of muscovites yielded a ^40Ar/^39Ar isochron age of 358 ± 2 Ma （ n = 23, MSWD = 11 ）. This shows that the ore bodies have been formed in Devonian. In the ore field, the magmatites, such as granitic porphyries, yielded isotope ages ranging from 428 to 466 Ma, which predated mineralization by 〉 40 Ma; while the ore-hosting stratum was suggested to have been formed around 1130 Ma, which predated mineralization by 〉 700 Ma. This evidenced that the Bainaimiao deposit is neither of porphyry-type nor of submarine sedimentary-exhalative type. Instead, it should be an orogenic-type deposit as revealed by a recently completed comprehensive study in ore geology and fluid inclusions. The mineralization ages consist with both the peak-metamorphism （ ca. 384.5 ± 6 Ma） of the orehosting rocks of the Bainaimiao Group and the late Silurian-Devonian collision of the Ondor Sum accretionary magmaitc arc on the northern margin of North China craton. Hence the Bainaimiao Cu-Au deposit is the first case of orogenic-type Cu deposit formed in collisional-orogenic regime.
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2008年第4期890-898,共9页
Acta Petrologica Sinica
基金
国家重点基础研究发展规划项目(编号:2006CB403500)
国家自然科学基金项目(编号40502011,40425006,40730421)资助。
关键词
白乃庙铜金矿床
中亚造山带
内蒙古
成矿年龄
造山型铜矿
Bainaimiao Cu-Au deposit
Central Asia Orogen
Inner Mongolia
Isotope age
Orogenic-type copper deposit
