【摘要】 桃子窝锡矿位于莲花山断裂带西段,是典型的火山-次火山岩型锡矿。本文以桃子窝锡矿赋矿火山-次火山岩及花岗岩为研究对象,首次开展LA-ICP-MS锆石U-Pb定年和Hf同位素特征研究。获得两个次火山岩样品的锆石206Pb/238 U加权平均年龄为172.1±1.1 Ma和171.8±0.9 Ma,一个花岗岩样品的锆石206 Pb/238 U加权平均年龄为168.9±1.5 Ma,表明桃子窝锡矿火山-侵入岩为中侏罗世同一岩浆事件不同阶段的产物。锆石εHf(t)值大多数为负值,只有3个点的值大于0,变化于-13.96~9.53之间,平均值为-7.92。在εHf(t)-t图解上,εHf(t)值大多落在球粒陨石演化线之下,有3个点落在球粒陨石与亏损地幔演化线之间。二阶段模式年龄除3个点介于609.6~795.5 Ma外,其余点年龄为1 450.8~2 102.5 Ma,Hf同位素特征指示成岩物质主要来源于早中元古代古老地壳的部分熔融,还有新元古代新生地壳物质的加入。结合区内已有的研究成果,认为桃子窝锡矿及有关的火山-次火山岩与中生代太平洋板块向欧亚大陆俯冲有关。更多还原

【Abstract】 The Taoziwo tin deposit located in the west of Lianhuashan faulted belt is a typical volcanic-subvolcanic tin deposit.With the ore-bearing volcanic-subvolcanic rock and granite in the Taoziwo tin deposit as the study objects,the authors performed in situ zircon U-Pb dating and Hf isotopic analyses for the first time.Two samples of volcanic-subvolcanic rocks yielded weighted average 206Pb/238 U ages of 172.1±1.1Ma and 171.8±0.9Ma respectively.A granite sample yielded the weighted average 206Pb/238 U age of 168.9±1.5 Ma.These data indicate that they were formed at different stages of the same Middle-Jurassic magmatic event.Most ofεHf(t)values are negative,except for threeεHf(t)values which vary from-13.96 to 9.53 with the mean value being-7.92.In theεHf(t)-t diagram,εHf(t)values are mostly beneath the chondrite evolution line with three points between the chondrite evolution line and the depleted mantle evolution line.All the two-stage model ages are between 1 450.8Ma and 2 102.5Ma except for three points which lie in the range of 609.6~795.5Ma,indicating that rock-forming materials were mainly derived from the partial melting of ancient early-middle Proterozoic crust with the addition of some juvenile Neoproterozoic crustal materials.In combination with the previous research results,the authors consider that the Taoziwo tin deposit and the related volcanic-subvolcanic rocks were genetically associated with the subduction of the Pacific plate to the Eurasian continent.更多还原