现代地质2018，Vol.32Issue(1)：28-44,17.DOI:10.19657/j.geoscience.1000-8527.2018.01.03
滇西丽江地区新生代富碱斑岩年代学、地球化学特征及其地质意义
Characteristics of Chronology and Geochemistry for the Cenozoic Alkali-rich Porphyry in Lijiang Area, Western Yunnan and Their Significance
摘要
Abstract
The Cenozoic alkali-rich porphyry in Lijiang region of Western Yunnan is located in the connection part between Sanjiang fold orogenic belt and southwest of Yangtze plate,including alkali rock and alkali-granite.Alkali rock includes orthophyre,syenite and trachyte-prophyry,while alkali granite includes granite-prophyry,monzonitic granite-prophyry and masanophyre.The zircon U-Pb dating indicates that the ages of those porphyry are between 34.6 and 37.1 Ma,which is consistent with the ages of Cenozoic alkali-rich porphyry in Western Yunnan.Geochemical results showed that alkali rock belongs shoshonite series,with SiO2 content of 54.54％-67.70％,K2O ＞ Na2O.Alkali-granite belongs high-K calc-alkalic series,with SiO2 content of 67.16％-70.66％,K2O ＜ Na2O.They are both enriched in alkali (Na2O + K2O =7.03％-11.70％),showing metaluminous and weak peraluminous (A/CNK =0.64-1.15) characteristics.The porphyry shows alkali and adakitic geochemical characteristics,with enrichment of LREE and LILE (Sr,Ba,K,Pb,and so on),deficit of HREE and HFSE (Nb,Ta,Ti,and so on),with high Sr content and ratio of Sr/Y,La/Yb,low Y and Yb contents,and low values of Mg# (＜ 0.5).The comprehensive study shows that the porphyry is associated with partial melting of the base of thickened lower crust caused by decompression melting and underplating of mantle-derived magmas,formed from the structure transition phase of late-collisional between Indian and Asian continents,and was the magmatic event response to syn-collisional processes in the structural transform zone of southeast of the Tibetan orogen.It is considered that there is great gold-polymetallic prospective reserves of porphyry-hydrothermal deposits.This paper provides important constraints for understanding deeply the tectonicmagmatic-metallogenic processes of the Lijiang porphyry metallogenetic belt.关键词
新生代富碱斑岩/锆石U-Pb定年/地球化学/丽江地区/滇西Key words
Cenozoic alkali-rich porphyry/zircon U-Pb geochronology/geochemistry/Lijiang area/Western Yunnan引用本文复制引用
黄永高,罗改,张彤,熊昌利,贾小川,杨学俊..滇西丽江地区新生代富碱斑岩年代学、地球化学特征及其地质意义[J].现代地质,2018,32(1):28-44,17.基金项目
中国地质调查局项目“西南三江有色金属资源基地调查”(DD20160016). （DD20160016）
