湖南瑶岗仙复式岩体的年代学特征

Chronological Characteristics of the Yaogangxian Composite Pluton in Hunan Province

瑶岗仙复式岩体位于湖南省东南部,属于南岭花岗岩北带,它是瑶岗仙钨矿床的成矿母岩。根据野外接触关系和岩石学特征将瑶岗仙复式岩体划分为三个期次的侵入岩,即第一期的粗粒黑云母花岗岩、第二期的细粒斑状花岗岩和第三期的石英斑岩。对瑶岗仙复式岩体进行锆石SHRIMP定年,分别得到三期岩体的年龄为155.4±2.2Ma(MSWD=0.53)、157.6±2.6Ma(MSWD=1.5)、158.4±2.1Ma(MSWD=1.17)。三期岩体形成时代很接近,矿物学特征相似,它们是同一岩浆房脉动事件的产物。综合前人研究成果可知,南岭地区在150～160Ma之间出现了花岗岩成岩事件以及与之相关钨锡成矿事件大爆发。瑶岗仙复式岩体的成岩事件和瑶岗仙钨矿床的成矿事件在时间和空间上高度吻合,二者密切相关,是连续的地质事件,是燕山早期南岭地区成岩成矿事件大爆发的代表。

The Yaogangxian composite pluton lies in the southeast of Hunan province,belonging to the north of Nanling granitoid zone.It is parental rock of the Yaogangxian tungsten deposit.The lithologies of the intrusions include coarse grained biotite granite formed in the first stage,fine grained granite in the second stage,and granite porphyry in the third stage.The crystallization ages of the intrusions were determined by using SHRIMP U-Pb zircon dating.The zircon SHRIMP U-Pb isotopic ages are defined as 155.4±2.2Ma（MSWD=0.53）,157.6±2.6Ma （MSWD=1.5） and 158.4±2.1Ma（MSWD=1.17） for the first,second and third stages of intrusions,respectively.Based on the range of zircon SHRIMP ages and mineral characteristics of these rocks,we inferred that they were products of pulsation events in the same magma chamber.In combination with previous research results,it is well known that granitoid intrusion and related tungsten-tin mineralization was an explosive regional event,and predominately took place during 150 to 160 Ma in Nanling area.Diagenesis of the Yaogangxian compsite pluton are closely related with mineralization.They are highly coincidence both in time and in space,and so to say,a continuous geological event.They are important parts of the explosive regional event in Nanling area.