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U–Pb SHRIMP monazite ages of the giant Morro Velho and Cuiabá gold deposits, Rio das Velhas greenstone belt, Quadrilátero Ferrífero, Minas Gerais, Brazil [查看] L.M.Lobato、J.O.S.Santos、N.J.McNaughton、I.R.Fletcher、C.M.Noce

U–Pb SHRIMP results of 2672±14 Ma obtained on hydrothermal monazite crystals, from ore samples of the giant Morro Velho and Cuiabá Archean orogenic deposits, represent the first reliable and precise age of gold mineralization associated with the Rio das Velhas greenstone belt evolution, in the Quadrilátero Ferrífero, Brazil. In the basal Nova Lima Group, of the Rio das Velhas greenstone belt, felsic volcanic and volcaniclastic rocks have been dated between 2792±11 and 2751±9 Ma, coeval with the intrusion of syn-tectonic tonalite and granodiorite plutons, and also with the metamorphic overprint of older tonalite–trondhjemite–granodiorite crust. Since cratonization and stable-shelf sedimentation followed intrusion of Neoarchean granites at 2612+3/−2 Ma,it is clear that like other granite–greenstone terranes in the world, gold mineralization is constrained to the latest stages of greenstone evolution.

辽宁凌源柏杖子金矿区花岗岩SHRIMP锆石U-Pb年龄 [查看] 罗镇宽、李俊建、关康、裘有守、Y.M.Qiu、N.J.McNaughton、D.I.Groves

采用SHRIMP测年方法测得柏杖子金矿区含矿花岗岩的锆石U-Pb年龄为(222±3)Ma，与区内都山花岗岩基和三家子金矿区花岗斑岩的年龄一致，属中生代印支期后碰撞花岗岩。该年龄限定了金矿化年龄的下限，即金矿化不可能早于印支期，但并不能确定金矿化的精确年龄。根据金矿脉与后期岩脉伴生的特征，矿化可能发生在中生代燕山期。