New insights on the age of the Mengyejing Formation in the Simao Basin,SE Tethyan domain and its geological implications

作者：Maodu YAN,Dawen ZHANG,Xiaomin FANG,Weilin ZHANG,Chunhui SONG,Chenglin LIU,Jinbo ZAN,Miaomiao SHEN

摘要：Knowledge on the origin and mechanism of the large potash formation in the southeast Tethyan tectonic domain are still under debate,one of which mainly due to the controversial ages of the potash-bearing strata.Here we present a detailed detrital zircon U-Pb geochronologic-magnetostratigraphic study of the potash-bearing Mengyejing(MYJ)Formation(Fm)from the Simao Basin.948 paleomagnetic cores and 4 detrital zircon U-Pb samples were collected from a 932-m thick Jiangcheng section.Thermal demagnetization isolated 857 primary characteristic remnant magnetization(ChRM)directions,indicated by positive reversals and fold tests and petrologic examinations.Seven normal and seven reversed polarity zones were identified and correlated well with chrons C27r to C34n of the geomagnetic polarity timescale(GPTS2012),yielding the first known age sequence of>112 to~63 Ma for the MYJ Fm.The ages for the potash bearing strata in the Simao commenced~20 Ma earlier than those in the adjacent Khorat basins,opposite to the traditional viewpoint that the former would rather correspond to the middle and lower parts of the latter.Given the paleogeographic reconstruction of likely a pan-Simao-Khorat basin during the Cretaceous,~85 Ma would be another important potential period for future potash exploration in the Simao Basin.

发文机构：Key Laboratory of Continental Collision and Plateau Uplift Center for Excellence in Tibetan Plateau Earth Sciences College of Tourism and Environmental Resource University of Chinese Academy of Sciences School of Earth Sciences MLR Key Laboratory of Metallogeny and Mineral Assessment

关键词：SimaoBasinMAGNETOSTRATIGRAPHYPotash-bearingsequenceMengyejingFm>112–~63MaPotashformation

分类号： P54[天文地球—构造地质学]