“三江”地区火山成因块状硫化物矿床的基本特征与主要类型

“三江”地区是我国一个主要的火山成因块状硫化物成矿区域,包括2个成矿带:①赠科—乡城矿带,主要产出伴随晚三叠世义敦岛弧裂谷火山作用形成的黑矿型Zn-Pb-Cu块状硫化物矿床;②昌宁—孟连矿带,以伴随保山—掸邦微陆块晚古生代裂谷火山作用形成的老厂型Pb-Zn-Cu和别子型Cu-Zn块状硫化物矿床为主,本文揭示“三江”地区,尤其是赠科—乡城和昌宁—孟连矿带的构造-火山-矿床的地质特征,阐明该区块状硫化物矿床的主要成因类型。

Volcanogenic massive sulfide deposits in Sanjiang region, Southwest China: geological features and main types

Volcanogenic massive sulfide (VMS) deposits and occurences so far discovered in Sanjiang region, Southwest China, are noted to be distributed mainly in the Zengke-Xiangcheng and the Changning-Menglian metallogenic belt. Ore deposits occurring within the Zengke-Xiangcheng belt are associated particularly with the uppermost Triassic felsic volcanic series which constitutes a component part of the bimodal volcanic suite formed during the Yidun interarc rifting. They are characterized compositionally by Zn>Pb>Cu and are comparable with Kuroko type VMS deposits, although fluid inclusions and H, O, S, Pb isotopic compositions of the representative deposits such as Gacun and Gayiqlong suggest an ore-forming fluid more akin to magmatic genesis. Two types of VMS deposits have been recognized in the Changning-Menglian belt, which were associated with different stages of rifting along the margin of the Baoshan-Shah State continental microplate. The Laochang type deposits, represented by Laochang ore district, are typically Pb>Zn>Cu in composition and are contained in the Upper Paleozoic alkaline basaltic-andesitic sequence formed in the initial Changning-Menglian riil basin, where the base- ment of Baoshan-Stan Shate microplate might have served as an important source for ore constituents, especially Pb and Zn. The Besshi type deposits such as Tongchangjie, noted for Cu>Zn, occur in the Upper Paleozoic tholeiitic volcanic rocks which were formed in an advanced Changning-Menglian rift basin, where metals were partially supplied by selective leachinz from the newly-formed oceanic crust. It is evident that the VMS deposits in Sanjiang region generally occur in groups in subbasins near volcanic centers and were formed during the extensional pariod of the volcanic arc or continental rift.