Middle to Late Triassic granitoids in the Qimantage area, Qinghai Province, China: Chronology, geochemistry and metallogenic significances
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摘要:
地处柴达木盆地西南缘的青海祁漫塔格地区不仅是一个特征显著的构造-岩浆岩带,而且也是重要的多金属成矿带。本文对该区中晚三叠世花岗岩开展了详细的年代学、岩石地球化学及Sr-Nd-Pb同位素组成研究,并探讨了成矿意义。结果表明,本区中晚三叠世花岗岩均系准铝质到弱过铝质高钾钙碱性花岗岩类,晚三叠世花岗岩具有更高的K2O/Na2O比值,富集大离子亲石元素(LILE)和轻稀土元素(LREE),明显亏损高场强元素(HFSE),中等初始锶比值和偏负的εNd(t)值表明它们主要源于古老地壳物质的深熔或重熔,并可能有幔源物质的加入;发育闪长质暗色微粒包体的中三叠世花岗岩锆石U-Pb年龄为230~237Ma,大多具斑状或似斑状结构的晚三叠世高分异富钾花岗岩形成于204~228Ma,表明大约240Ma祁漫塔格主造山已由挤压转入伸展并伴有幔源岩浆活动,晚三叠世后演化到后碰撞阶段;中晚三叠世花岗岩与本区密集产出的矽卡岩型和斑岩型多金属矿床的时空与成因关系密切,具有重要找矿指示意义。
Abstract:The Qimantage area, located on the southwestern margin of Qaidam Basin, is not only a characteristic intrusive magmatic tectonic belt, but also a very important poly-metallic metallogenic belt. In this paper, detailed geochronological, element geochemical, Sr-Nd-Pb isotopic studies were carried out for the Middle to Late Triassic granitoids, and relationship between granitoids and poly-metallic mineralization was discussed. The Middle to Late Triassic granitoids in Qimantage area are characterized by the metaluminous to peraluminous and high-K calc-alkaline rocks. Of them, the Late Triassic granitoids is much enriched in K2O/Na2O ratio, LILE and LREE, and poor in HFSE. The rocks exhibit moderate initial 87Sr/86Sr values and comparatively negative εNd(t) values, which indicate that they were derived from ancient crust sources and mixed probably by mantle material. The precise U-Pb zircon dating results define emplacement of the mianthite-riched granodiorite occurred during 230~237Ma, Late Triassic porphyritic granitiods intruded at 228~204Ma. It is inferred that the tectonic transformation from crustal compression to extension was produced at about 240Ma, and was accompanied by mantle source magmatism. The occurrence of Late Triassic high differentiated and high-K calc-alkaline granitoids indicates that this area had evolved into post-collisional environment. The large numbers of porphyry and skarn-type poly-metallic deposits are temporally and spatially related to Middle to Late Triassic granitic intrusions.
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Key words:
- Granitoids /
- Geochemistry /
- Geochronology /
- Middle to Late Triassic /
- Post-collisional environment /
- Qimantage /
- Eastern Kunlun
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常有英, 李建放, 张军, 曹生秀, 李萍萍, 陈海清. 2009. 青海那陵郭勒河东晚三叠世侵入岩形成环境及年代学研究. 西北地质, 42(1): 57-65
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丰成友, 李东生, 屈文俊, 杜安道, 王松, 江军华. 2009. 青海祁漫塔格索拉吉尔矽卡岩型铜钼矿床辉钼矿Re-Os同位素定年及其意义. 岩矿测试, 28(3): 223-237
丰成友, 李东生, 吴正寿, 李军红, 张占玉, 张爱奎, 舒晓峰, 苏生顺. 2010. 东昆仑祁漫塔格成矿带矿床类型、时空分布及多金属成矿作用. 西北地质, 43(4): 10-17
丰成友,王雪萍,舒晓峰,张爱奎,肖晔,刘建楠,马圣钞,李国臣,李大新. 2011. 青海祁漫塔格虎头崖铅锌多金属矿区年代学研究及地质意义. 吉林大学学报(地球科学版),41(6):1806-1817
郭正府, 邓晋福, 许志琴, 莫宣学, 罗照华. 1998. 青藏东昆仑晚古生代末-中生代中酸性火成岩与陆内造山过程. 现代地质, 12(3): 344-352
李光明, 沈远超, 刘铁兵. 2001. 东昆仑祁漫塔格地区华力西期花岗岩地质地球化学特征. 地质与勘探, 37(1): 73-78
李世金, 孙丰月, 丰成友, 刘振宏, 赵俊伟, 李玉春, 王松. 2008. 青海东昆仑鸭子沟多金属矿的年代学研究.地质学报, 82(7): 949-955
刘成东, 莫宣学, 罗照华, 喻学惠, 谌宏伟, 李述为, 赵欣. 2004. 东昆仑壳-幔岩浆混合作用: 来自锆石SHRIMP年代学的证据. 科学通报, 49(6): 592-602
刘云华, 莫宣学, 喻学惠, 张雪亭, 许国武. 2006. 东昆仑野马地区景忍花岗岩锆石SHRIMP U-Pb定年及其地质意义. 岩石学报, 22(10): 2457-2463
佘宏全, 张德全, 景向阳, 关军, 朱华平, 丰成友, 李大新. 2007. 青海省乌兰乌珠尔斑岩铜矿床地质特征与成因. 中国地质, 34(2): 306-314
宋彪, 张玉海, 万渝生, 简平. 2002. 锆石SHRIMP样品靶制作、年龄测定及有关现象讨论. 地质论评, 48(增刊): 26-30
王松, 丰成友, 李世金, 江军华, 李东生, 苏生顺. 2009. 青海祁漫塔格卡尔却卡铜多金属矿区花岗闪长岩锆石 SHRIMP U-Pb测年及其地质意义. 中国地质, 36(1): 74-84
奚仁刚, 校培喜, 伍跃中, 董增产, 过磊, 高晓峰. 2010. 东昆仑肯德可克铁矿区二长花岗岩组成、年龄及地质意义. 西北地质, 43(4): 195-202