广西镇龙山岩浆热液成矿系统——来自成矿流体、成矿物质的证据

Magmatic-hydrothermal metallogenic system in Zhenlongshan,Guangxi:Evidence from ore-forming fluids and materials

镇龙山岩浆热液成矿系统位于广西“山字形构造”前弧一个较大的短轴背斜构成的穹窿中,矿床(点)主要赋存于寒武系和泥盆系碎屑岩中。为探讨各矿床(点)之间的成因联系,在野外调查的基础上,对典型矿床进行了流体包裹体测温、激光拉曼及氢-氧-硫同位素研究。研究结果表明,包裹体主要为水溶液、气液两相包裹体,且含CO 2和CH_(4)包裹体较多,偶见含NaCl子晶的包裹体。高温矿床均一温度为320~339℃,盐度为8%~9%NaCl eqv;中温矿床均一温度为280~299℃,盐度为7%~8%NaCl eqv;低温矿床均一温度为160~179℃,盐度为5%~6%NaCl eqv。石英中流体包裹体δD V-SMOW集中在-55‰~-80.1‰之间,δ^(18)O_(V-PDB)集中在-9.1‰~-18.8‰之间,氢-氧同位素图解主要落在岩浆水的范围内,并有向大气降水偏移的趋势,表明上述矿床流体的主要来源可能是岩浆水,后期有大气降水的混入。单矿物的硫同位素峰值集中在-2‰~2‰之间,其中毒砂以正值为主,辉锑矿以负值为主,总体具有相对均一的硫源,说明硫化物中的硫均来自岩浆。上述研究表明,镇龙山地区矿床(点)分布具有明显的岩浆-热液成矿系统的分带特点,岩体及其边缘发育斑岩型高温热液矿床,外围逐渐过渡到中温和中低温热液矿床,建立了镇龙山地区岩浆热液成矿系统的水平和垂直矿化分带模型。

The Zhenlongshan magmatic hydrothermal metallogenic system is located in the dome formed by a large short axis anticline in the front arc of the"mountain shaped structure"in Guangxi.The deposits(occurrence)mainly occur in the Cambrian and Devonian clastic rocks.Fluid inclusion thermometry,laser Raman,and H-O-S isotope studies were conducted on typical ore deposits.The system elucidated the source of ore-forming fluids,characteristics and evolution of ore-forming fluids,and sources of ore-forming materials for gold,silver,copper,lead,and zinc deposits around the porphyry,and preliminarily explored the genetic connections of various ore deposits(occurrence)around the porphyry.The results show that the inclusions are mainly gas-liquid inclusions,and contain more CO 2 and CH_(4) inclusions,and occasionally contain NaCl daughter crystals.The homogenization temperature of high temperature deposit is 320~339℃,and the salinity is 8%~9%NaCl eqv;the homogenization temperature of medium temperature deposit is 280~299℃,and the salinity is 7%~8%NaCl eqv;the homogenization temperature of low temperature deposit is 160~179℃,and the salinity is 5%~6%NaCl eqv.That is,with the decrease of homogenization temperature,salinity also decreases.TheδD V-SMOW andδ^(18)O_(V-PDB)of quartz concentrate in-55‰~-80.1‰and-9.1‰~-18.8‰.The H-O isotopic diagram is mainly in the range of magmatic water and tends to shift to meteoric water,which indicates that the main source of fluid in the above deposit may be magmatic water,and there is the mixing of meteoric water in the later stage.The sulfur isotope peak values are concentrated in the range of-2‰~2‰,in which arsenopyrite is mainly positive and stibnite is mainly negative.Generally,there is a relatively uniform sulfur source,indicating that the sulfur in sulfide comes from magma.The above research shows that the distribution of ore deposits(occurrence)in Zhenlongshan area has obvious zoning characteristics of magmatic hydrothermal metallogenic system.Porphyry high temperature hydrothermal deposits are developed in the pluton and its edge,and the periphery gradually transits to medium and low temperature hydrothermal deposits.The horizontal and vertical mineralization zoning model for the magmatic hydrothermal metallogenic system in Zhenlongshan area are established.