摘要
北衙金多金属矿床是金沙江-哀牢山-红河断裂带与新生代富碱斑岩有关的斑岩型矿床之一。本文重点提供了流体包裹体中稀土微量元素和矿石S、Pb同位素分析结果,并对成矿流体及成矿物质来源等问题进行了讨论。研究表明,本区流体包裹体稀土总量较低,∑REE介于5.19×10-6～9.0×10-6之间,反映轻重稀土分馏程度的∑LREE/∑HREE比值和(La/Yb)N分别为4.12～11.25和9.56～17.65,表现为轻稀土明显富集型,流体包裹体与该区富碱斑岩的稀土配分模式基本一致。矿石的S和Pb同位素分析结果显示,本区不同矿段不同硫化物矿石黄铁矿、方铅矿和黄铜矿的S和Pb同位素组成没有明显差异,其208Pb/204Pb、207Pb/204Pb和206Pb/204Pb分别变化在38.256～39.0394,15.457～15.703和18.380～18.673范围内,且与富碱斑岩的S、Pb同位素组成十分相近。结合已有流体包裹体气液相成分研究成果,提出北衙金铜多金属矿床的成矿流体主要来自富碱斑岩岩浆的深部分异作用,在流体上升过程中可能受到地壳物质的混染。成矿物质具有与成矿流体相同的深部来源。因此,富碱斑岩岩浆作用不仅为含矿流体上升提供了动力和热能,同时也是成矿物质和成矿流体的主要来源和载体。
The Beiya gold-polymetallic deposit is one of the typical deposits related to Cenozoic alkali-rich porphyry along the Jingsha River-Ailaoshan-Red river fault system in western Yunnan Province.This presents measurements on the trace elements of fluid inclusions and S-Pb isotopes of ores,and discusses the characteristics of ore-forming fluids and the material sources of ore formation.The results show that the total REE abundance is relatively low,with a range from 5.19 to 9.0×10^-6,whilst LREE/HREE and （La/Yb）N reflecting fraction between LREE and HREE vary from 4.121 to 11.249 and from 9.563 to 17.651,respectively.The distribution patterns of REE display a LREE-enriched trend,which is roughly consistent with that of alkali-rich porphyries.The δ34S values are in the range of -2.4~4.5‰ and the ^208Pb/^204Pb,^207Pb/^204Pb and ^206Pb/^204Pb values range from 38.256 to 39.0394,from 15.457 to 15.703,and from 18.380 to 18.673,respectively.There is no obvious variation in the sulfur and lead isotopic composition for different sulfides （pyrite,galena and chalcopyrite） from different ore blocks,and the S-Pb isotopic compositions are also very similar to that of alkali-rich porphyries.In combination with the previous studies of fluid inclusions,it could be concluded that alkali-rich porphyry magma not only provides a driving force and heat for the rise of ore-bearing fluids,but also acts as the main source and carrier for the ore-forming material and mineralization fluid.
出处
《地质与勘探》
CAS
CSCD
北大核心
2011年第2期170-179,共10页
Geology and Exploration
基金
国家重点基础研发发展规划项目《三江岩浆作用与壳幔交换成矿制约》编号:2009CB42100
自然科学基金(编号:40972049,40572046)
关键词
金多金属矿
稀土微量元素
硫、铅同位素
滇西北衙
gold polymetallic deposit
trace elements and rare earth elements
sulfur and lead isotope
Beiya in western Yunnan
