滇西北甭哥碱性岩有关金矿床多阶段剥蚀历史和保存示踪:磷灰石裂变径迹热年代学证据  

Multi-stage Exhumation and Preservation of the Bengge Alkaline-related Gold Deposit in Northwestern Yunnan Province, SW China: Evidence from Apatite Fission-track(AFT) Thermochronology

作　　者：张荣伟[1,2] 彭建堂[1,2] 薛传东[3] 薛力鹏 徐恒 ZHANG Rongwei;PENG Jiantang;XUE Chuandong;XUE Lipeng;XU Heng(School of Geosciences and Info-Physics,Central South University,Changsha 410083,Hunan,China;MOE Key Laboratory of Metallogenic Prediction of Nonferrous Metals and Geological Environment Monitoring,Central South University,Changsha 410083,Hunan,China;Department of Earth Sciences,Kunming University of Science and Technology,Kunming 650093,Yunnan,China;Yunnan Nonferrous Geological & Geophysical & Geochemical Exploration Survey,Kunming 650216,Yunnan,China)

机构地区：[1]中南大学地球科学与信息物理学院,湖南长沙410083 [2]中南大学有色金属成矿预测与地质环境监测教育部重点实验室,湖南长沙410083 [3]昆明理工大学地球科学系,云南昆明650093 [4]云南省有色地质局地质地球物理化学勘查院,云南昆明650216

出　　处：《大地构造与成矿学》2019年第5期943-952,共10页Geotectonica et Metallogenia

基　　金：国家重点基础研究发展规划973项目(2015CB452601);国家自然科学基金项目(41272096、41462003)联合资助

摘　　要：造山带背景下矿床的矿后剥蚀历史及保存示踪研究,有助于理解区域成矿作用和指导找矿勘查与评价。滇西北甭哥金矿床是一个与印支期碱性岩有关的热液型金多金属矿床,金储量已达中型规模,但对其矿床成因和成矿潜力仍不明朗。该矿床处在西南三江造山带北段与扬子地台西缘的交汇地带,是香格里拉印支.燕山期巨型斑岩.矽卡岩型Cu-Au-Mo多金属矿集区的组成部分,是开展矿床剥蚀历史及保存示踪研究的理想地区。本文以甭哥金矿区含矿碱性岩体为研究对象,通过系统的剖面实测、样品采集和磷灰石裂变径迹测试,经热史模拟,估算其隆升历史及剥蚀深度。结果表明,甭哥金矿区自喜马拉雅期以来主要经历了42~32Ma、32~16Ma和16~6Ma三期隆升.剥蚀事件,三组年龄较好地限制了其构造热事件活动时限,该构造事件在西南三江地区具有普遍一致性;含矿岩体的隆升量及隆升速率分别为5852~6422m和0.21~0.39mm/a,剥蚀量和剥蚀速率分别为2130m和0.07~0.14mm/a;其最大剥蚀量远小于成矿深度,表明该矿床形成后的剥蚀程度弱,保存状况较好,尚具有较大的找矿前景。Reconstruction of exhumation history and preservation status of ore deposits in orogenic belts is critical for regional metallogenic study and mineral resource evaluation and prospecting. The Bengge gold deposit, a hydrothermal type gold-polymetallic deposit with gold reserve of more than 6 tons, is genetically related to Indosinian alkali-rich porphyries in Northwestern Yunnan province. Up to now, the ore-forming mechanism and its mineral potential at depth are still unclear. This deposit is located in the intersection between the northern Sanjiang orogenic belt and the west margin of the Yangtze platform, which is also a representative ore deposit in the giant Shangri-La Indosinian and Yanshanian alkali-rich porphyry-skarn type Cu-Au-Mo-polymetallic ore concentrated area. Therefore, it is an ideal locus for investigations of the post-ore denudation and preservation conditions of the ore deposits. Through systematical profile measurement, sample collection and apatite fission-track (AFT) ages testing, this paper simulates the thermal history of the alkali-rich rocks in the Bengge gold deposit, illustrates the differential uplift and exhumation across the orefield, and appraises the deep metallogenic potential. Three tectonic thermal periods were recognized in the orefield, i.e., 42.32 Ma, 32.16 Ma, and 16.6 Ma, respectively. The three age groups represent intervals of rapid cooling and exhumation during the Himalayan epoch, which are broadly consistent with those in the Sanjiang orogenic belt and the southeastern margin of the Tibetan Plateau. The calculated results show a mean uplift of 5852 m to 6422 m at a rate of 0.21 mm/a to 0.39 mm/a, and a mean exhumation rate of 0.07 mm/a to 0.14 mm/a with a total estimated denudation of ca. 2130 m for the Bengge ore-bearing alkali-rich porphyries. Accordingly, the denudation is much less than that the depth of petrogenesis or ore mineralization of the Bengge gold deposit. Therefore, our model calculation demonstrates that the post-ore denudation effect on the deposits i

关 键 词：磷灰石裂变径迹 热史反演 隆升 剥蚀 甭哥金矿床 滇西北 

分 类 号：P597.3[天文地球—地球化学] P613[天文地球—地质学]