国家自然科学基金项目（面上项目，重点项目，重大项目）
鱼洞子杂岩是秦岭造山带出露的重要太古宙基底，也是该地区最古老的复杂地质体。鱼洞子杂岩主要由变质地层（鱼洞子岩群）和规模不等的花岗质变质侵入体组成。各地质体间多以构造面理接触。鱼洞子岩群是重要的铁矿产出层位，铁矿及其赋矿围岩的形成时代一直没有可靠的依据。本次选择小沟山矿区磁铁石英岩分选出大量锆石。CL影像特征显示锆石普遍具有清晰的幔-边结构，幔部发育较清晰的震荡环带，显示典型的岩浆锆石特征；边部为灰白色后期变质环带。依据锆石CL影像特征，结合锆石成因分析，通过锆石微区U-Pb同位素LA-ICPMS（激光剥蚀等离子体质谱）测定，获得鱼洞子小沟山矿区磁铁石英岩岩浆锆石不一致线上交点年龄为2645±25Ma（MSWD=1.2），207Pb/206Pb加权平均年龄为2645±24Ma，二者极为一致，代表石英岩原岩（中酸性火山岩）的形成时代。同时获得变质锆石较好的不一致线上交点年龄为2555±24Ma（MSWD=1.4），与207Pb/206Pb加权平均年龄2527±27Ma在误差范围内较为一致，应为火山岩发生变质形成磁铁石英岩的时代，是太古宙一次重要的区域变质事件信息的反映。
Yudongzi complex, the significant occurrence horizon of iron mine , is the most important Archean basement and the oldest geological mass in the Qinling area. It is mainly composed of metamorphic strata (Yudongzi group) and granitic metamorphic intrusions with unequal size, most of which contact with structural foliation. Based on CL image features of zircon, combined with genetic analysis of zircon and microdomains U-Pb isotope LA-ICP-MS (laser ablation ICP-MS) determination, we obtained an upper intercept age of 2645±25Ma（MSWD=1.2）and an weighted mean 207Pb/206Pb age of 2645±24Ma for the magnetite-quartzite magmatic zircons in Xiaogoushan mine area. The consistent data represents the protolith formation age of quartzite , the original rock of which is intermediate-acid volcanic rocks. The upper intercept age 2555±24Ma（MSWD=1.4）for the metamorphic zircons we have also got, is consistent with the weighted mean 207Pb/206Pb age of 2527±27Ma within the error range, and indicates the metamorphic age of quartzite from volcanic. From above we can say that the age reflects an important regional metamorphism event in Archean.
王洪亮,徐学义,陈隽璐,闫臻,李婷,朱涛.2011.南秦岭略阳鱼洞子岩群磁铁石英岩形成时代的锆石U-Pb年代学约束[J].地质学报,85(8):1284-1290.
WANG Hongliang, Xu Xueyi, Chen Junlu, Yan Zhen, Li Ting, Zhu Tao.2011. Constraint from zircon U-Pb chronology of Yudongzi group magnetite-quartzite in Lueyang area, southern Qinling, China[J]. Acta Geologica Sinica,85(8):1284-1290.
