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陈喜连,黄文婷,邹银桥,梁华英,张健,张玉泉. 2016. 玉龙斑岩铜矿带南段含矿斑岩体锆石U-Pb年龄、地球化学特征及南北段成矿规模差异分析. 岩石学报, 32(8): 2522-2534
玉龙斑岩铜矿带南段含矿斑岩体锆石U-Pb年龄、地球化学特征及南北段成矿规模差异分析
作者单位E-mail
陈喜连 中国科学院广州地球化学研究所, 中国科学院矿物学与成矿学重点实验室, 广州 510640
中国科学院大学, 北京 10004 
 
黄文婷 中国科学院广州地球化学研究所, 中国科学院矿物学与成矿学重点实验室, 广州 510640  
邹银桥 中国科学院广州地球化学研究所, 中国科学院矿物学与成矿学重点实验室, 广州 510640
中国科学院大学, 北京 10004 
 
梁华英 中国科学院广州地球化学研究所, 中国科学院矿物学与成矿学重点实验室, 广州 510640 lianghy@gig.ac.cn 
张健 中国科学院广州地球化学研究所, 中国科学院矿物学与成矿学重点实验室, 广州 510640
中国科学院大学, 北京 10004 
 
张玉泉 中国科学院广州地球化学研究所, 中国科学院矿物学与成矿学重点实验室, 广州 510640  
基金项目:本文受国家“973”项目(2015CB452602)和国家自然科学基金项目(41421062)联合资助.
摘要:
      藏东缘玉龙斑岩铜矿带是中国重要的产于碰撞造山环境下的斑岩铜矿带,其全长约300千米,主要由1个超大型、2个大型、2个中型斑岩铜矿床及一系列斑岩型矿床(点)组成。玉龙斑岩铜矿带大规模矿化主要位于矿带北段,南段矿化规模相对较小,目前发现的多为小型矿床(点)。为了深入了解玉龙斑岩铜矿带时空演化及南北段矿化规模差异的控制因素,本文分析了玉龙斑岩铜矿带南段色礼、马牧普和总郭这3个矿化点矿化斑岩体锆石LA-ICP-MS U-Pb年龄、地球化学组成及色礼矿化斑岩体锆石Hf同位素。色礼、马牧普和总郭含矿斑岩分别为二长花岗斑岩、正长斑岩及石英二长斑岩,三者锆石LA-ICP-MS U-Pb年龄分别为39.4±0.2Ma(MSWD=1.10)、38.5±0.3Ma(MSWD=1.79)和39.4±0.2Ma(MSWD=1.05)。矿化斑岩体为偏铝质,具有富碱、高钾(K2O/Na2O=1.2~2.4)、富集大离子亲石元素和轻稀土元素,亏损高场强元素,弱Eu负异常特征。3个矿化斑岩具有较高的Sr/Y比值,且都发育角闪石斑晶,呈现富水岩浆特征。色礼二长花岗斑岩的锆石εHft)为-2.7~2.8,平均值为-0.4,显示壳幔混合源区特征,并且其明显小于玉龙斑岩铜矿带北段玉龙超大型斑岩铜矿床含矿斑岩体锆石εHft)值(4.2)。玉龙斑岩铜矿带南北段含矿斑岩体形成时代相近,都形成于碰撞造山走滑构造背景。玉龙超大型矿床矿化斑岩锆石εHft)值明显大于色礼矿化点斑岩体锆石εHft)的值,表明矿床规模和岩浆源区物质含幔源物质多少有关,更多亏损地幔物质或新生地壳物质的加入更有利于形成大型斑岩矿床。玉龙斑岩铜矿带南北段成矿规模差异可能为北段斑岩体含更多地幔或新生地壳物质所致。
英文摘要:
      The Yulong porphyry copper belt located in eastern Tibet is one of the most important porphyry copper belts formed in post-collisional setting in China. It is about 300km in length and consists of one giant, two large and two medium-sized porphyry copper deposits, as well as a series of small-sized porphyry deposits (occurrences). The giant and large porphyry copper deposits occurred mainly in the northern Yulong porphyry copper belt while the small-sized deposits or ore occurrences are found so far in the southern Yulong porphyry copper belt. To understand the temporal and spatial evolution of the whole Yulong porphyry copper belt more deeply and figure out the reasons why there are big differences in the scale of mineralization between the north and the south of the Yulong porphyry copper belt, this paper analyzes the zircon LA-ICP-MS U-Pb ages and geochemistry characteristics of the Seli, the Mamupu and the Zongguo ore-bearing porphyries in the southern Yulong porphyry belt, in addition to the zircon Hf isotope composition of the Seli porphyry. The Seli, the Mamupu and the Zongguo porphyries associated closely with mineralization are monzongranite porphyry, syenite porphyry and quartz monzonite porphyry, respectively. The Seli monzogranite porphyry, the Mamupu syenite porphyry and the Zongguo quartz monzonite porphyry have zircon LA-ICP-MS U-Pb age of 39.4±0.2Ma with MSWD=1.10, 38.5±0.3Ma with MSWD=1.79 and 39.4±0.2Ma with MSWD=1.05, respectively. The ore-bearing porphyries are metaluminous and characterized by enrichment in alkali with high K2O/Na2O ratio (K2O/Na2O=1.2~2.4), LREE and LILE, depleted in HFSE, as well as weak negative Eu anormaly. All the three porphyries contain hornblende phenocrysts and have high Sr/Y ratios, suggesting that their primary melts are water-rich. In situ zircon Hf isotopic composition of the Seli monzongranite porphyry shows εHf(t) values ranging from -2.7 to 2.8 with the average of -0.4, which indicates the source area is a mixture of continental crust and mantled-derived material, and these εHf(t) values are obviously lower than those (with an average of 4.2) of the Yulong giant porphyry copper deposit. The forming ages of ore-bearing porphyries in the southern Yulong porphyry copper belt are similar to those in the northern ore belt and the formation of the Yulong porphyry copper belt is genetically related to the activities of large-scale strike-slip fault systems triggered by the continental collision of India with Asia. The εHf(t) values of ore-bearing porphyry in Yulong giant deposit are higher than that of Seli small deposit which implies that the scale of porphyry copper deposit is related to the content of mantle-derived materials involved in the source of magma, and the more mantle-derived materials involve, the better for the formation of large scale porphyry copper deposit it will be. The differences of ore size between the southern and northern Yulong porphyry copper belt are probably due to that the porphyries in the northern area derived from the sources with more contribution from mantle or juvenile crust.
关键词:斑岩铜矿床  锆石年龄  地球化学特征  玉龙斑岩铜矿带  西藏东部
投稿时间:2016-02-01  修订日期:2016-05-24
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