摘要
位于扬子陆块西缘与西南三江造山带结合部位的乡城-丽江地区，北起四川乡城经云南格咱南至丽江地区，在印支期斑岩铜矿带上新发现叠加了燕山期斑岩Mo多金属成矿作用，形成乡城-丽江斑岩Mo矿带。受印支期古特提斯洋盆闭合后地壳缩短与加厚的影响，燕山晚期下地壳发生拆沉作用，导致后碰撞型花岗质岩浆侵位，发育了Mo多金属成矿作用，并构成斑岩成矿系统。岩石地球化学特征表明，燕山晚期含矿斑岩具高硅（SiO2=66.29%～79.36%）、高碱（K2O＋Na2O=5.07%～9.24%）、富钾（K2O/Na2O=0.71～2.13）的特点，属于高钾钙碱性岩石系列。岩石富集轻稀土元素（LREE），具有负δEu异常；微量元素具富集大离子亲石元素K、U、Th、Rb，亏损高场强元素Nb、Ta、P、Ti的特征；大离子亲石元素的富集和Nb、Ta等高场强元素的亏损，表明形成这些岩体的岩浆主要来自地壳，具有造山带花岗岩的地球化学特征。区内代表性含矿斑岩相似的地球化学组成及分布特征表明，乡城-丽江结合带燕山晚期的成矿斑岩是由同源岩浆分异演化而来。成矿系统的分析表明，燕山晚期主要含矿斑岩成矿物质以壳源为主，但具有少量地幔物质的加入，成岩成矿物质来源具有相似或一致的源区特征。在成矿元素的组合上，由成矿斑岩体向外带表现出W、Mo→W、Mo、Cu→Pb、Zn、Ag的演化趋势。研究表明，本区燕山晚期花岗岩浆的侵入及Mo多金属成矿作用并不是独立或个别的成矿事件，而是纵跨义敦岛弧、甘孜-理塘结合带及扬子西缘的带状成矿活动，属于区内与燕山晚期岩浆侵入作用相关的统一斑岩成矿系统。
Xiangcheng-Lijiang suture zone located in combined position of the western margin of Yangtze block and Sanjiang orogenic belt, it north to Xiangcheng of Sichuan, through Geza of Yunnan, south to Lijiang area, in which newly discovered that porphyry copper belt of Late Triassic superimposed porphyry Mo-polymetallic mineralization in Late Cretaceous and formed Xiangcheng-Lijiang porphyry molybdenum belt. In Late Cretaceous, by Tethys basin closed and crustal shortening and thickening, lower crustal delamination and post-collision-type granitic magma intrusion developed Mo-polymetallic mineralization, which formed the porphyry metallogenic system. The lithogeochemical characteristics shown that Late Cretaceous ore-bearing porphyry with the characteristics of high silicon （SiO2=66.29%~79.36%）, high alkali （K2O＋Na2O=5.07%~9.24%）, richen potassium （K2O/Na2O=0.71~2.13）, which belongs to the K-high calc-alkali rock series. Rock enriched LREE and LILEs （K, U, Th, Rb） and depleted in HFSEs （Nb, Ta, P, Ti）; enriched in LILEs and depleted in HFSEs （Nb, Ta） shown that the magma which formed these rocks are mainly from the crust and has the geochemical characteristics of orogenic granitoids. Similar geochemical composition and distribution characteristics of representative ore-bearing porphyry in this area shown that ore-forming porphyry in Xiangcheng-Lijiang suture zone was derived from the differentiation and evolution of the same source magma in Late Cretaceous. By analysis of metallogenic system, the metallogenic materials of ore-bearing porphyry are mainly derived from the crust, but with a small amount of mantle material added, rock-forming and metallogenic meterials with the similar or consistent source region characteristics. In the combination of ore-forming elements, from the metallogenic porphyry body to the outer zone shown that the evolutional trend of W, Mo→W, Mo, Cu→PbZn, Ag. This study shown the intrusion of the Late Cretaceous granite magma and the Mo-polymetallic mineralization i
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2016年第8期2281-2302,共22页
Acta Petrologica Sinica
基金
国家重点基础研究发展计划"973"项目(2015CB452605)
国家自然科学基金项目(41502076)
中国地质调查局项目(12120114013701)联合资助
关键词
斑岩
Mo多金属矿床
成矿系统
成矿物质来源
燕山晚期
乡城.丽江结合带
Porphyry
Mo-polymetallic deposits
MetaUogenic system
Source of ore-forming materials
Late Cretaceous
Xiangcheng-Lijiang suture zone
