兰坪盆地银铜钴镍多金属矿床黝铜矿系列矿物学特征及其成因意义

Mineralogy characteristic and the genetic significance of tennantite-tetrahedrite from Ag-Cu-Co-Ni polymetal deposits in Lanping basin,Yunnan,China

云南兰坪盆地内的银铜多金属矿床以产大量黝铜矿系列矿物为特征.黝铜矿系列矿物是主要的载银矿物,大多属银黝铜矿系列,Ag含量最高可达46.4%,Ag原子数最高为6.64.存在四大系列黝铜矿,即:(1)锑砷黝铜矿系列,置换Cu元素的主要为Fe和Zn,其中Fe的原子数低于Zn,Zn明显优势于Fe;(2)砷黝铜矿系列,置换Cu元素的主要为Fe和Zn,二者含量及原子数变化较大,其中金满铜矿床中出现大量的块状铁砷黝铜矿;(3)锑铋砷黝铜矿的Sb原子数可以很低,置换Cu元素的主要是Fe和Zn,Zn的原子数大于Fe;(4)砷锑黝铜矿系列,该类矿物主要产于富隆厂矿段中,与独立银矿物辉银矿、自然银、螺状硫银矿等共生.黝铜矿各元素含量和原子数之间的变化特征表明,Ag-Cu, Ag-As, Ag-Fe之间存在明显的负相关,而Ag-Sb、部分矿区Ag-Zn之间存在明显的正相关.热液脉型矿床产出的黝铜矿显示为Zn原子数高、Fe原子数低,Fe原子数一般小于0.8,Zn原子数一般在1～2之间.当Fe原子数小于 0.5时,Ag原子数高,最高达6.64,其中富隆厂矿段的黝铜矿的Ag原子数平均达0.94.整个盆地内银铜多金属矿床的黝铜矿系列矿物的As-Sb原子数呈极好的线性负相关,大部分黝铜矿的As原子数大于1,以砷黝铜矿占优势.当Sb原子数大于0.5时,有利于Ag占据更高的黝铜矿原子数,并具显著的正相关关系.

The distinguished feature of the Ag-Cu polymetal deposits in Lanping basin is the occurrence of large quantity of tetrahedrite series minerals, which are the main Ag-bearing minerals. Most of those are Ag-bearing tetrahedrite, in which the content of Ag is up to 46.4%, and the atomicity is 6. 635. Those minerals can be divided into four kinds： （1） Sb-As tetrahedrite series. The main elements exchanging for Cu are Fe and Zn. And the atomicity of Zn is greater than that of Fe. Obviously Zn is more than Fe. （2）Tennantite series. The main elements exchanging for Cu are Fe and Zn. The contents and atomicities of Fe and Zn vary comparatively greatly. There is one exception, that is, in the Jinman Cu deposit, plenty of iron blende appears. （3） Sb-Bi tennantite series. The atomicity of Sb is very small. The main elements exchanging for Cu are Fe and Zn, and the atomicity of Zn is greater than that of Fe. （4）As-Sb tetrahedrite series. This series minerals mainly appear in the Fulongchang ore belt, coexisting with independent Ag-bearing minerals-argentite, silver and acanthite. From the variation features of the element content and atomicity of tetrahedrite series minerals, it can be inferred that Ag and Cu, Ag and Fe, Ag and As are negatively interrelated, respectively, and Ag and Sb, Ag and Zn are positively interrelated, respectively. The Zn atomicity of tetrahedrite within a thermal fluid vein deposit is great and the Fe atomicity is small. Generally the atomicity of Fe is smaller than 0.8, and that of Zn is 1-2. When the atomicity of Fe is smaller than 0. 5, the atomicity of Ag is great and the maximum is up to 6. 635. And the Ag atomicity of tetrahedrite within the Fulongchang ore belt averages 0. 9424. In Ag-Cu polymetal deposits around the whole basin, the relation between As and Sb atomicities of tetrahedrite is strictly negative linear correlation. The As atomicity of most tetrahedrite is greater than 1, indicating that tennantite is in dominant position. When the atomicity of Sb is greater than 0.5, it is preferable to Ag to have a great atomicity, and the atomicity of Ag and Sb are positively interrelated.