西藏谢通门县斯弄多大型叠加改造型铅锌矿床特征及找矿方向

斯弄多铅锌矿区位于冈底斯斑岩型矿床成矿带中。矿区花岗斑岩和闪长玢岩的地球化学特征表明,斯弄多铅锌矿与冈底斯斑岩型矿床为同一成矿体系,均形成于印—亚大陆主碰撞期和碰撞期后的构造体制转化阶段;岩浆来源于原岩以杂砂岩和泥质岩为主的前寒武纪念青唐古拉群变质结晶基底和下地壳基性岩类的部分熔融。成矿物质主要来源于雅鲁藏布江新特提斯洋对冈底斯弧俯冲板片的部分熔融并交代岛弧带上的基底岩系。矿床的形成分为3期:第一期为中石炭世,与碳酸盐岩沉积同时期的海底热水喷流沉积作用形成初始矿源层;第二期为构造活动成矿期,分2个成矿阶段:第一阶段为晚白垩世—始新世,即印-亚大陆主碰撞形成的早期与斑岩有关的岩浆热液型铅锌矿;第二阶段的铅锌矿化发生在主碰撞期后的伸展拉张阶段,由于花岗斑岩的侵位,使铅锌矿化进一步活化迁移、叠加、富集,与围岩接触部位形成夕卡岩型铅锌矿体,矿体的形成多受矿区内复杂的断裂构造控制,矿床类型主要为构造破碎带热液充填型和夕卡岩型;第三期为表生期,主要为原生硫化矿体的氧化流失和贫化。在I号矿带的深部、南部和北部异常区具有扩大矿床规模的远景。

Characteristics of Sinongduo large-size overprinted and reworked Pb-Zn deposit in Xietongmen County of Tibet and the ore-searching directions

The Sinongduo Pb-Zn deposit is located in the Gangdese porphyry copper ore belt. Geochemistry of the granitic porphyry and dioritic porphyry shows that Sinongduo Pb-Zn deposit and the Gangdesetype porphyry deposits belong to the same metallogenic system and they were formed during and after the structure transitional period of Indian-Asia plate collision. The magma comes from the partial melting of the basement gneiss of the Precambrian Nyainqentanglha Group, which dominantly derives from greywacke and argillaceous rocks in crust, and the basaltic rocks in lower crust. Ore-forming materials originated from partial melting subduction slab of the Yarlu Zangbo Neo-Tethyan Ocean crust under the Gangdese magmatic arc and replacement of the basement of island arc by the melted materials. The formation of the ore deposit is divided into three periods. The first period was the Middle Carboniferous at which Sedex bed was formed contemporarily with carbonate rocks as the source bed. The second period was the tectonic mineralization period which was further divided into two mineralization phases. The first phase was the Late Cretaceous to the Eocene during which early hydrothermal Pb-Zn mineralization related to porphyry that may be resulted from Indian-Asia plate collision occurred. The second one is the post main Indian-Asia plate collision stretching phase at which Pb-Zn mineralization occurred and Pb, Zn from the mineralization was remobilized, overprinted and enriched due to emplacement of granitic porphyry and skarn type Pb-Zn ore bodies were formed at contact between the porphyry and the surrounding rocks and were generally controlled by complex fractures (faults). The deposits were mainly of the structural fracture zone hydrothermal fluid filling and Skarn types. The third period is mainly supergene mineralization, i.e., dilution of the primary sulfide ore body caused by oxidation and removal of Pb, Zn oxides. The anomaly areas in south and north of the deposit are potential for further exploration.