东天山黄土坡铜锌矿床成矿流体的氦-氩同位素示踪

Helium and argon isotope characteristics of ore-forming fluids for the Huangtupo copper-zinc deposit, eastern Tianshan

黄土坡铜锌矿床是东天山卡拉塔格地区一中型海相火山岩型块状硫化物（VHMS）矿床，赋存于早志留世海相火山—沉积岩系中。矿体产于酸性火山角砾岩与凝灰岩之间，主矿体呈厚大的扁豆状，矿石主要呈块状、浸染状、条带状和网脉状构造。本文报道了黄土坡铜锌矿床成矿流体的氦和氩同位素组成，黄铁矿流体包裹体的^3He 含量低，介于0.039×10^-12 cm^3 STP/g～0.64×10^-12 cm^3 STP/g，n（^3He）/n（^4He）值为 0.11～0.94 Ra，介于壳源He与幔源He之间。^40Ar 含量变化于 3.49×10^-8cm^3 STP/g～34.25×10^-8 cm^3 STP/g 之间，n（^40Ar）/n（^36Ar）介于301.40～425.98 之间。成矿流体中有幔源 He（1.71%～10.97%）和放射性成因 Ar（^40Ar^＊含量为1.96%～30.63%）。结合矿床包裹体及 H-O-S 同位素特征，认为幔源流体和富放射性成因He 和Ar 的海水参与了成矿。

The Huangtupo middle copper-zinc deposit is located at the central part of Kalatage copper polymetallic belt in eastern Tianshan. This deposit belongs to volcanic hosted massive sulfide deposit（VHMS）or volcanogenic massive sulfide deposit（VMS）,which is hosted in the Early Silurian marine volcaniclastic-sedimentary sequence. The ore bodies are hosted in intermediate volcanic breccias and felsic tuff assemblages with massive orebody at the upper and vein orebody at the lower part. The structures of ores are massive, disseminated, banded and veinlet. This paper reports He and Ar isotopic data of fluid inclusions trapped by pyrites.^3 He/ ^4He ratios range from 0.11 to 0.94 Ra with He derived from mantle varying from 1.71% to 10.97%. ^40Ar/ ^36Ar ratios range from 301.40 to 425.98 with ^40Ar^＊ content from 1.96% to 30.63% . Combining inclusions assemblages, hydrogen, oxygen and sulfur isotopic characteristics of the Huangtupo copper-zinc deposit, it can be concluded that the mantle-derived fluids and seawater containing crustal ^4He and atmospheric Ar were involved in the mineralization, and the seawater is dominated.