尹川 1严冰 2刘图强 1龙文昌 3温彬 3段利 3韩耀成3
作者信息
- 1. 四川省地质矿产(集团)有限公司,四川 成都 610036
- 2. 成都理工大学,四川 成都 610059
- 3. 四川省地质矿产(集团)有限公司,四川 成都 610036||四川省博达地质勘查研究有限公司,四川 成都 610036
- 折叠
摘要
Abstract
The Caiyuanzi gold deposit in Muli,Sichuan Province,is located in the southern section of the Ganzi-Litang ophiolitic mélange belt and is a large-scale gold deposit(Au resources>20 t)discovered in recent years.The orebody positioning is controlled by the brittle-ductile shear structural system above the ductile shear zone.However,previous studies lack a systematic understanding of the intrinsic relationship between the ductile shear zone and the genesis of the deposit,which has constrained the understanding of ore-controlling regularities and the determination of further exploration directions.To clarify the genetic type of this deposit,this work systematically investigated the characteristics of the ductile shear zone,ore-controlling structures,ore-forming fluid features,and gold precipitation mechanisms through methods including field geological profiles,drill core logging,microstructural observation,fluid inclusion petrography and microthermometry,laser Raman spectroscopy,and H-O and S isotope analyses.Results show that:(1)The shear zone experienced superimposed modification from early deep sinistral ductile shearing to late shallow brittle-ductile shearing.The ore bodies are strictly controlled by the brittle-ductile shear structural system,displaying a left-stepping en echelon arrangement in plan view,constituting a Riedel shear ore-controlling structure.(2)The ore-forming fluid is characterized by medium-low temperature(homogenization temperature:104.5～405.7℃,peak at 260～280℃),low salinity(avg.8.29%NaCleqv),and medium-low density(avg.0.87 g/cm³),belonging to the H2O-NaCl-CH4-CO2 system.H-O isotopes(δD=-116.2‰ to-76.0‰,δ18OH2O=3.6‰ to 6.5‰)and S isotopes(δ34S=10.0‰ to 18.8‰)indicate that the ore-forming fluids and materials were mainly derived from deep metamorphic fluids,with meteoric water added during the late stage of mineralization.(3)Decompression boiling induced by spatial dilation is the dominant mechanism for gold precipitation.(4)The genetic type of the deposit can be classified as a ductile shear zone-type gold deposit,with the mineralization type being structurally altered rock type.Based on the regional geological evolution background,it is proposed that the formation of the Caiyuanzi gold deposit is related to the post-orogenic crustal extension and thinning of the Songpan-Garzi orogenic belt during the Yanshanian period.Accordingly,a four-stage metallogenic model is established:initial gold emplacement,gold source formation,gold migration and enrichment,and gold precipitation.This study aims to provide a reference for the exploration of similar deposits within the Ganzi-Litang metallogenic belt.关键词
韧性剪切带型金矿/脆-韧性剪切构造/成矿流体/成矿机制/菜园子金矿床/甘孜-理塘成矿带Key words
ductile shear zone-type gold deposit/brittle-ductile shear structure/ore-forming fluid/metallogenic mechanism/Caiyuanzi gold deposit/Ganzi-Litang metallogenic belt分类
天文与地球科学
