贵州习水洞子沟铅锌矿床闪锌矿微量元素特征与成因

Characteristics of trace elements of sphalerite and genesis of the Dongzigou lead-zinc deposit in Xishui County, Guizhou Province,China

贵州习水县洞子沟铅锌矿床位于桑木场背斜核部,矿体呈层状、似层状、脉状产出于灯影组白云岩中,矿石矿物以闪锌矿为主,脉石矿物主要为重晶石、白云石。对单矿物的微量元素ICP-MS分析结果表明,该矿床闪锌矿相对富集Cu、Zn、Pb、Ba、Ga、Ag、Ge等元素,而Mn、Fe、Cd、In、Mo、Se、Tl等相对较贫,其Ga/In(118.83~968.33)、Ge/In(471.88~14079.40),Zn/Cd(196.94~246.27),Zn/Fe(24.67~384.95)比值相似于中低温铅锌矿床闪锌矿,暗示其形成于中低温环境。总体上,洞子沟铅锌矿床闪锌矿微量元素组成特征与喷流沉积型、岩浆热液型铅锌矿床区别明显,而与一些典型MVT型铅锌矿(如马元铅锌矿、大梁子铅锌矿、天桥铅锌矿等)类似,结合该矿床地质特征,本文认为洞子沟铅锌矿成因类型属于非典型的MVT类型。

The Dongzigou lead-zinc deposit, located in core of the Sangmuchang anticline, has stratiform, stratoid or veined orebodies in dolomite of the Dengying Formation, with ore mineral of sphalerite and gangue minerals of barite and dolomite. The ICP-MS analytical results of trace elements show that the sphalerite contains relatively enriched Cu, Zn, Pb, Ba, Ga, Ag, and Ge, but relatively depleted Mn, Fe, Cd, In, Mo, Se, and Tl, with ratios of Ga/In(118.83-968.33), Ge/In(471.88-14079.40), Zn/Cd(196.94-246.27), and Zn/Fe(24.67-384.95) similar to those of the medium-low temperature lead-zinc deposit, suggesting that the sphalerite was formed under the medium-low temperature. Generally, trace element characteristics of the sphalerite of the Dongzigou lead-zinc deposit are significantly different from those of the Sedex type and magmatic hydrothermal type lead-zinc deposits, but similar to those of some typical MVT type lead-zinc deposits(e.g. Mayuan, Daliangzi, Tianqiao). Combining with the geological characteristics, this study suggests that the Dongziou lead-zinc deposit belongs to atypical MVT type.