黔东牛角塘大亮锌矿矿物学与成矿温度研究

Study on mineralogy and metallogenic temperature of Daliang Zn deposit in Niujiaotang ore field,eastern Guizhou

大亮锌矿是牛角塘铅锌矿田的重要组成部分,目前所开采的对象为近年来在“陡倾斜带”中新发现的矿体,其研究还十分薄弱。利用显微镜详细研究了大亮锌矿的矿物学特征,对挑选出的主成矿阶段的闪锌矿进行了ICP-MS微量元素测试,对矿物组成、矿石组构、围岩蚀变、矿物生成顺序及成矿温度进行了研究。结果表明,矿石矿物主要为闪锌矿和黄铁矿,脉石矿物主要为白云石,发育致密块状、浸染状、脉状、角砾状及团块状构造,以自形—半自形、他形和包含结构为主,可分为沉积—成岩期、成矿期和表生期。近矿围岩蚀变以黄铁矿化、白云石化和深色化为主,还包括重晶石化、方解石化、沥青化和萤石化,前三种蚀变与成矿密切相关,有利于锁定矿体范围,提高找矿效率。闪锌矿微量元素含量最高的为Cd和Fe,其次为Pb和Cu,含有一定量的Ga、Mn和Ge,少量的Sn、Ba、Ag、Ni、Sr、Cr、Sb和As和极少量的Tl、W、Li、In、Co、Rb、V、Mo、Zr、Cs、Sc、Bi、Y、Be和U元素。闪锌矿主要为浅黄色,其低Fe,富Cd、Ga和Ge和低In/Ga与In/Ge比值的特征暗示其形成温度较低。根据Fe、Ga、Ge、Mn和In估算其成矿温度范围为87~155.15℃(平均133.21℃),第一主成分PC1*值(0.98~2.23,平均1.38)与密西西比河谷型(MVT)铅锌矿床(1.37)几乎一致。因此,大亮锌矿属于低温MVT矿床。

The Daliang Zn deposit is an important part of Niujiaotang Pb-Zn ore field.The mining object is the newly discovered ore body in the"steep dip zone"in recent years,and the research on it is still very weak.The mineralogical characteristics of Daliang Zn deposit have been studied in detail by microscope,and the sphalerites in the main metallogenic stage have been selected for ICP-MS trace element test.The mineral composition,ore fabric,wall rock alteration,mineral formation sequence,and metallogenic temperature have been studied.The results show that the ore minerals are mainly sphalerite and pyrite,and the gangue minerals are mainly dolomite.The ores are characterized by dense massive,disseminated,veined,brecciated,and nodular structures,and mainly consists of hypidiomorphic to automorphic,allotriomorphic,and inclusion texture.The formation of Daliang Zn deposit have gone through three periods:depositional to diagenetic period,metallogenic period,and supergene period.The wall rock alterations near the ore body are mainly pyritization,dolomitization,and darkening,and also include baratization,calcilization,bituminization,and fluoritization.The first three kinds of alterations are closely related to mineralization,which are conducive to locking the orebody range and improving the prospecting efficiency.The contents of trace elements in sphalerites are highest of Cd and Fe,followed by Pb and Cu,a certain amount of Ga,Mn,and Ge,a small amount of Sn,Ba,Ag,Ni,Sr,Cr,Sb,and As,and a very small amount of Tl,W,Li,In,Co,Rb,V,Mo,Zr,Cs,Sc,Bi,Y,Be,and U.Sphalerites are mainly light yellow,with low Fe,rich Cd,Ga,and Ge,and low In/Ga and In/Ge ratios,suggesting that the temperature at which they form is low.Based on the trace elements Fe,Ga,Ge,Mn,and In,it is estimated that the ore-forming temperature ranges from 87℃to 155.15℃with an average value of 133.21℃,and the first principal component PC1*value(vary from 0.98 to 2.23,mean=1.38)is almost consistent with that of the Mississippi Valley-type(MVT)Pb-Zn deposit(1.37).Therefore,the Daliang Zn deposit is a low temperature MVT deposit.