投稿时间：2021-09-01
修订日期：2022-04-11
网络发布日期：2022-07-07
中文摘要:铁坑坳铁锡多金属矿床位于粤东莲花山断裂带西部，矿区出露的花岗岩类主要有粗粒二长花岗岩和花岗闪长斑岩，花岗质岩石与碳酸盐岩的接触带中发育铁锡多金属矿化。该矿区的成岩成矿时代尚不明确，成矿与哪一种岩体具有成因上的联系也不清楚。文章选择与铁锡多金属矿体相关的花岗岩类的锆石和块状矿石中的锡石，首次开展LA-ICP-MS U-Pb定年和Nd-Hf同位素研究。结果表明：粗粒二长花岗岩和花岗闪长斑岩的锆石U-Pb年龄分别为（132±1） Ma （n=24，MSWD=0.78）和（94±1） Ma （n=25，MSWD=1.80）；块状矿石中锡石U-Pb年龄为（130±3） Ma （n=36，MSWD=0.62），成矿时代与粗粒二长花岗岩形成时代基本一致，均形成于早白垩世；粗粒二长花岗岩的锆石εHf （t）变化于-4.9~-0.1，平均值为-2.8，地壳Hf模式年龄TDMC=1192~1497 Ma，平均值为1366 Ma，全岩εNd （t）值介于-8.8~-8.7，Nd同位素二阶段模式年龄TDM2变化于1630~1642 Ma；花岗闪长斑岩的锆石εHf （t）变化于-5.7~-2.9，平均值为-4.4，地壳Hf模式年龄TDMC=1342~1523 Ma，平均值为1440 Ma，全岩εNd （t）值介于-5.4~-4.9，Nd同位素二阶段模式年龄TDM2变化于1291~1332 Ma。Nd-Hf同位素综合研究表明，粗粒二长花岗岩的源区物质主要来自于中元古代地壳，有少量幔源组分或新生地壳的加入，花岗闪长斑岩的源区物质中幔源组分或新生地壳的混入比例高于粗粒二长花岗岩。
Abstract:The Tiekeng'ao Fe-Sn polymetallic deposit is located in the west of the Lianhuashan fault zone in eastern Guangdong Province. Granites exposed at the deposit include coarse-grained monzonitic granite and granodioritic porphyry. The massive Fe-Sn polymetallic ore bodies occur within the contact zone between granite and carbonates. The ages of mineralization and magmatic intrusions at the Tiekeng'ao deposit are unclear, hindering a better understanding of the magmatic processes and their relations with metallogenesis. Here, we carried out LA-ICPMS U-Pb dating and Nd-Hf isotope studies of zircons and cassiterites extracted from granitoids and massive ores, respectively. Zircon LA-ICP-MS U-Pb dating of the coarse-grained monzonitic granites and granodioritic porphyry yielded concordant ages of (132±1)Ma (n=24, MSWD=0.78) and (94±1)Ma (n=25, MSWD=1.80), respectively. The U-Pb dating of the cassiterites from the massive ore is (130±3)Ma (n=36, MSWD=0.62), overlapping with the coarse-grained monzonitic granite within analytical error. Zircon εHf(t) values of coarse-grained monzonitic granites vary from -4.9 to -0.1 with an average value of -2.8. The crustal Hf model age (TDMC) is between 1192 Ma and 1497 Ma with an average age of 1366 Ma, and the whole rock εNd(t) values vary from -8.8 to -8.7. Neodymium isotope two-stage model age TDM2 varies between 1630 Ma and 1642 Ma. Zircon εHf(t) values of granodioritic porphyry range from -5.7 to -2.9, with an average of -4.4. The crustal Hf model age is between 1342 Ma and 1523 Ma, with an average of 1440 Ma. The εNd(t) of the whole rock ranges between -5.4 and -4.9, with the Nd isotope two-stage model age TDM2 varies between 1291 Ma and 1332 Ma. The Nd-Hf isotopic composition indicates that the coarse-grained monzonitic granite is initially derived from the Mesoproterozoic crust, with a small proportion of mantle and juvenile crust components contamination. In contrast, the granodioritic porphyry is mainly derived from the partial melting of the Mesoproterozoic crust with a more significant proportion of mantle and juvenile components.
keywords:geochemistry cassiterite U-Pb dating zircon LA-ICP-MS U-Pb dating Nd-Hf isotope granitoid genesis Tiekeng'ao Fe-Sn polymetallic deposit eastern Guangdong
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基金项目:本文得到国家重点研发计划项目（编号：2017YFC0601403）、中国地质调查局项目（编号：DD20201173、DD20221684）联合资助
引用文本：
张志涛,柯昌辉,徐林刚,马收先,陈懋弘,叶会寿,潘玉峰.2022.粤东铁坑坳铁锡多金属矿床锆石及锡石U-Pb年代学、Nd-Hf同位素特征及其意义[J].矿床地质,41(3):543~566ZHANG ZhiTao,KE ChangHui,XU LinGang,MA ShouXian,CHEN MaoHong,YE HuiShou,PAN YuFeng.2022.Zircon and cassiterite U-Pb geochronology and Nd-Hf isotope geochemistry of Tiekeng'ao Fe-Sn polymetallic deposit in eastern Guangdong and its geological significance[J].Mineral Deposits41(3):543~566
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