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笔者在西藏西南部普兰盆地填1:10万地质图时,发现了一条沿盆地东缘展布的新生代伸展断层,其上盘为上新世普兰组(N_2pl)砾岩;下盘为前寒武纪聂拉木群(AnZny)花岗片麻岩及花岗质糜棱岩和碳酸质糜棱岩。糜棱岩的拉伸线理为WNW向,倾角平缓。在上下盘地层中都发育大小不同、近似平行的正断层,其中一条组成盆地东缘的大陡坎。侵位于断层下盘糜棱岩中变形与未变形的浅色花岗岩的Pb/Th法等离子探针年龄分别为19Ma和8Ma,该断层为藏南大型WNW向拆离伸展构造的组成部分。普兰盆地的形成很可能与右旋的喀喇昆仑的活动有关。
In the 1: 100,000 geology map of the Plains basin in southwestern Tibet, the author discovered a Cenozoic extensional fault distributed along the eastern margin of the basin. Its upper plate is conglomerate of the Pliocene (N 2pl) Cambrian NeZny granitic gneiss and granitic mylonites and carbonate mylonites. Mylonite stretching lineage is WNW, gentle dip. In the upper and lower plate strata are developed in different sizes, approximately parallel to the normal fault, one of the basin composed of the eastern margin of the large steep ridge. The Pb / Th plasma probes ages 19Ma and 8Ma for the deformed and undeformed light-colored granites in the mylonites of the lower fault, respectively, are part of the large-scale WNW strike-detachment extension structure in southern Tibet. The formation of the Pulan Basin is probably related to the dextral Karakorum activities.