摘要
川西呷村含金富银多金属矿床是典型的黑矿型Zn-Pb-Cu-Ag矿床,其形成于与岛弧裂陷相伴的“双峰式”火山活动末期,产于岛弧裂谷带内的酸性火山岩系中。矿床由下部网脉状矿和上部块状矿组成,具“双层结构”金属分带和蚀变分带特征,矿体与喷气岩-喷气沉积岩密切伴生。成矿作用可分为四个阶段,每一阶段均形成特定的矿物共生组合。本文在已往研究基础上,拟就成矿流体的化学成分和热演变历史,探讨矿床金属分带、蚀变分带机理和成矿作用过程。
The Gacun auriferous and argeniferous polymetallic deposit in western Sichuan rovince is a typical uroko type Zn-Pb-Cu deposit formed at the terminal stage of 'double peak ype' volcanism associated with the island rc rifted depression and occurring in acid volcanic ystem within the island arc rifted zone. The ore deposit is omposed of network ores in the ower part and massive ores in the upper part, characterized by 'two-layer tructure', etallic oning and alteration zoning and accompanied with exhalite and iron-rich chemical sedimentary ock. The ore-orming process of the Gacun ore deposit might be divided into four stages with ach stage forming its own index ineral assemblage (phase). Homogenization temperatures of luid nclusions indicate that ore-forming temperatures f , Ⅲ and Ⅳ metallogenic stages are espectively 260—209℃, 320—262℃ and 100—185℃. Studies show that ore-orming temperatures f arious metallogenic stages and their evolution trend basically represent temperatures of re uids at various stages and their evolution trend. The network ore and the massive ore show imilar evolution trend f luid temperature (Ⅱ—Ⅲ—Ⅳ), revealing that the two sorts of ores ay in the same hydrothermal fluid system and ere ormed through the deposition of the same luid n different environments. Chemical composition of ore fluids was stimated by means of nclusion omposition determination and thermodynamic model, α_(H_2S) of ore fluids as restricted by fluid emperature. High temperature and high α_(H_2S) characters of ore luids at Stage Ⅲ led to the issolution and leaching of minerals of Phase Ⅰ and Phase Ⅱ, and the persistent recipitation f chalcopyrite and some other minerals gave birth to the initial metallic zoning, m_(∑SO_4~2-)) of ore luids was related to fluid composition and source. The gradual increase in m_∑SO_^(2-)) with time implies the orrsponding increase in proportion of seawater composition n ore fluids, and this accounts for the appearance of arge quantities of barite in Phase Ⅳ nd he stable distribution of barite layer at the top of the massive ore bed. H_S oncentration and ation concentration governed the crystallization order and deposition proportion of sphalerite nd alena: for ore fluids of No. Ⅱ metallogenic stage, m_(∑Zn)<m_(H_2S)<m_(∑Pb), and this ecided that sphalerite rystallized at first in this stage with the crystallization amount arger than that of galena. For ore fluids of No. Ⅳ tage, _(H_2S)<<m_(∑Pb) or m_(∑Zn), which ecided that crystallization amount and proportion of sphalerite and galena ad nothing to do ith Zn and Pb concentration of ore fluids.
出处
《矿床地质》
CAS
CSCD
北大核心
1991年第4期313-324,共12页
Mineral Deposits