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引用本文:赵希林 毛建仁 陈 荣 许乃政. 闽西南地区紫金山岩体锆石SHRIMP定年及其地质意义[J]. 中国地质, 2008, 35(4): 590-597.
ZHAO Xi-lin, MAO Jian-ren, CHEN Rong, XU Nai-zheng. SHRIMP zircon dating of the Zijinshan pluton in southwestern Fujian and its implications[J]. Geology in China, 2008, 35(4): 590-597(in Chinese with English abstract).
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闽西南地区紫金山岩体锆石SHRIMP定年及其地质意义
赵希林 毛建仁 陈 荣 许乃政
作者单位
赵希林 毛建仁 陈 荣 许乃政 南京地质矿产研究所江苏 南京 210016 
摘要:
提要:笔者通过锆石SHRIMP定年,精确厘定了紫金山岩体的成岩成矿时代。紫金山黑云母花岗岩中锆石CL图像显示锆石分为3种形态,定年结果显示这3种锆石有不同的年龄,具有不同的地质意义。第一种锆石晶形发育、具有核-边双层结构,核部的锆石呈磨圆状,这类锆石为继承性锆石,年龄为1000 Ma左右;第二种锆石晶形发育良好,但是呈不完整形态,有不清晰的生长环带或者无生长环带,呈现岩浆锆石的特征,年龄为168±4 Ma(n=13, MSWD=0.97),这一年龄应代表了岩石的结晶年龄,属于中侏罗世;第三种锆石晶形发育良好,有清晰的生长环带,这种锆石受后期改造作用,年龄为(119±15)Ma,属于早白垩世。(168±4) Ma时本区并未发生大规模的成矿事件,因此紫金山岩体主体并非含矿岩体,仅有轻微的锡矿化。紫金山花岗岩锆石SHRIMP定年的第三组年龄为(119±15)Ma是大规模成矿作用的记录,可能正是这一期的热液作用开始了本区大规模的长时期的多期次的岩浆热液作用的序幕,从而为本区铜金成矿作用奠定了基础。
关键词:  紫金山岩体  SHRIMP锆石定年  岩浆热液作用  成岩成矿
DOI:
分类号:
基金项目:中国地质调查局基础地质调查项目(1212010611805,300313000070)资助。
SHRIMP zircon dating of the Zijinshan pluton in southwestern Fujian and its implications
ZHAO Xi-lin, MAO Jian-ren, CHEN Rong, XU Nai-zheng
Abstract:
Abstract:The rock- and ore-forming ages of the Zijinshan pluton were precisely redefined based on SHRIMP zircon dating. CL images of zircons in the Zijinshan biotite granite show that there are three zircon morphologies. The results of dating indicate that the three types of zircon have different ages and different geological implications. The first type of zircon crystal is perfect and has core-rim structure. The core is rounded. This type of zircon is considered inherited zircons dated at ~1000 Ma. The second type of zircon has well-developed but incomplete crystal morphology. It is half-baked with indistinct growth zoning or no growth zoning, showing the features of magmatic zircons. The age of the zircons is 168±4 Ma, which represents the crystallization age of the pluton, indicating an Early Mesozoic Middle Jurassic age. The third type of zircon is perfect and has clear growth zoning. It has undergone late-stage reworking. Its age is 119±15 Ma, suggesting an Early Cretaceous age. There is no report of large-scale mineralization at 168±4 Ma in the study area; so the main part of the Zijinshan pluton is not a mineralized pluton, only showing weak tin mineralization. The third group of SHRIMP U-Pb ages is considered as the record of large-scale Cu-Au mineralization. It is possibly just this stage of hydrothermal processes that commenced the prologue to the large-scale, long-continued, multistage magmatic hydrothermal processes and thus laid a foundation for the copper-gold mineralization in the area.
Key words:  Zijinshan pluton  SHRIMP zircon dating  magmatic hydrothermal processes  petrogenesis and mineralization