| 南蒙古古生代岛弧地体中酸性岩石锆石年代学、Hf同位素特征及地质意义 |
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| 引用本文： | 张伟波,王丰翔,刘翼飞,江思宏,何学洲,于瑞,李谦谦.南蒙古古生代岛弧地体中酸性岩石锆石年代学、Hf同位素特征及地质意义[J].地球科学,2022,47(8):2824-2838. |
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| 作者姓名： | 张伟波 王丰翔 刘翼飞 江思宏 何学洲 于瑞 李谦谦 |
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| 作者单位： | 1.中国地质科学院矿产资源研究所自然资源部成矿作用与资源评价重点实验室, 北京 100037 |
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| 基金项目： | 中国地质调查局项目DD20211404中国地质调查局项目DD20190437中国地质调查局项目DD20190455 |
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| 摘 要： | 南蒙古曼达洛沃-古尔班赛汗岛弧地体是中亚造山带的重要组成部分，为了探讨岛弧地体内岩浆活动及地壳演化过程与斑岩型铜多金属矿床成矿作用的成因关系，对产出在该地体内代表性斑岩铜矿床与成矿作用有关的岩石进行了岩相学、锆石年代学及Hf同位素组成分析. 哈马戈泰铜-金矿床出露的与成矿有关的岩石为花岗闪长岩-二长闪长玢岩组合，LA?MC?ICP?MS锆石定年数据显示，成岩年龄为332~324 Ma；查干苏布尔加矿区产出有二长花岗斑岩，为铜-钼矿化的容矿岩体，本次测定的成岩年龄为~372 Ma；青狐狸斑岩型铜多金属矿化与闪长岩具有成因联系，本次测定的成岩年龄为~333 Ma；奥尤特乌兰铜多金属矿区岩浆岩活动强烈，产出有二长岩和安山岩-花岗闪长岩杂岩体，本次测定的成岩年龄分别为~381 Ma和338~332 Ma. 综上所述，曼达洛沃-古尔班赛汗岛弧地体晚古生代岩浆活动主要分为3个阶段:383~369 Ma、367~363 Ma和338~321 Ma. 其中，与斑岩铜多金属矿化有成因联系的岩浆活动主要集中在375~369 Ma和338~328 Ma两个时期，可能为该区域两个最重要的成矿期. 原位锆石εHf（t）位于球粒陨石演化线之上，介于+7.85~+16.14之间，部分分析点与亏损地幔值相似，显示成岩物质来源可能是亏损地幔部分熔融形成的新生物质在地壳短暂停留后再次部分熔融的产物，同时也受到了一定程度成熟地壳的混染. Hf同位素两阶段模式年龄tDM2为331~717 Ma，表明本区发生重要的地壳增生事件的时间是新元古代至晚古生代.
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| 关 键 词： | 南蒙古 岛弧 中酸性岩石 年代学 锆石Hf同位素 斑岩铜矿 |
| 收稿时间： | 2021-08-11 |
Zircon Geochronology and Hf Isotope of Intermediate Acidity Magmatic Rocks in the Island Arc Terrane of South Mongolia and Their Geological Significance |
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| Abstract: | The Mandalovoo?Gurvansaikhan island?arc Terrane in South Mongolia is an important part of Central Asian Orogenic Belt (CAOB). In order to constrain the genetic relationship between the large?scale magmatism, porphyry?type Cu?polymetallic mineralization and regional crustal evolution, petrography, LA?MC?ICP?MS zircon geochronology and Hf?isotop were completed on the typical deposits. Based on geological evidence, the metallogenic?related rocks at Kharmagtai Cu?Au deposit is the andesite?monzodiorite porphyritem, and the LA?ICP?MS zircon U?Pb dating of them yields crystallization age of 332 to 324 Ma. The monzonitic granite hosting the Tsagaan Suvarga Cu?Mo ore?bodies and the diorite granodiorite porphyry related to Bronze Fox porphyry?type mineralization yield crystallization age of ~372 Ma and ~333 Ma respectively. The monzonite intrusions and andesite?granodiorite complexes at Oyut Ulaan were emplaced at ~381 Ma and 338 to 332 Ma. Based on geological evidence, and chronology data, the Late Paleozoic magmatic activity at Mandalovoo?Gurvansaikhan island?arc Terrane is mainly divided into three stages: 383 to 369 Ma, 367 to 363 Ma and 338 to 321 Ma. Among them, the metallogenic?related magmatic active are mainly concentrated in two periods of 375 to 369 Ma and 338 to 328 Ma, which may be the two most important mineralization periods in the region. Moreover, the in?situ zircon εHf(t) show positive values between +7.85 to +16.14, which are above the chondrite evolution line, partial sample are markedly close to the depleted mantle (DM) evolution line, indicating that the source of the diagenetic material may be the new material formed by the DM partial?melting, and the new material subject to partial melting after a short stay in the crust, mixed with a certain amount of mature crust. The tDM2 are 331~717 Ma, indicating that the time of important crustal accretion events in region is from Neoproterozoic to Late Paleozoic. |
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