Oscillation of mineral compositions in Core SG-1b, western Qaidam Basin, NE Tibetan Plateau.
Uplift of the Tibetan Plateau since the Late Miocene has greatly affected the nature of sediments deposited in the Qaidam Basin. However, due to the scarcity of continuously dated sediment records, we know little about how minerals responded to this uplift. In order to understand this response, we here present results from the high-resolution mineral profile from a borehole (7.3-1.6 Ma) in the Basin, which shows systematic oscillations of various evaporite and clay minerals that can be linked to the variation of regional climate and tectonic history. In particular, x-ray diffraction (XRD) analyses show that carbonate minerals consist mainly of calcite and aragonite, with minor ankerite and dolomite. Evaporates consist of gypsum, celesite and halite. Clay minerals are principally Fe-Mg illite, mixed layers of illite/smectite and chlorite, with minor kaolinite and smectite. Following implications can be drawn from the oscillations of these minerals phases: (a) the paleolake was brackish with high salinity after 7.3 Ma, while an abrupt change in the chemical composition of paleolake water (e.g. Mg/Ca ratio, SO4(2-) concentration, salinity) occurred at 3.3 Ma; (b) the three changes at ~6.0 Ma, 4.5-4.1 Ma and 3.3 Ma were in response to rapid erosions/uplift of the basin;
Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100085, China.|Key Laboratory of Continental Collision and Plateau uplift, Institute of Tibetan Plateau Research, CAS, Beijing 100085, China.|CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing, 100101, China.
Xiaomin
X
Fang
Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100085, China.|Key Laboratory of Tibetan Environment Changes and Land Surface Processes, CAS, Beijing 100085, China.
Minghui
M
Li
Department of Earth and Atmospheric Sciences, City College of New York, CUNY, New York, NY 10031, USA.
Zhengrong
Z
Wang
Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100085, China.|Key Laboratory of Continental Collision and Plateau uplift, Institute of Tibetan Plateau Research, CAS, Beijing 100085, China.
Jiuyi
J
Wang
Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100085, China.|Key Laboratory of Continental Collision and Plateau uplift, Institute of Tibetan Plateau Research, CAS, Beijing 100085, China.|University of Chinese Academy of Sciences, Beijing 100049, China.
Jiao
J
Li
Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100085, China.|Key Laboratory of Continental Collision and Plateau uplift, Institute of Tibetan Plateau Research, CAS, Beijing 100085, China.
Xiaoming
X
Liu
Institute of Tibetan Plateau Research, Chinese Academy of Sciences (CAS), Beijing 100085, China.|Key Laboratory of Continental Collision and Plateau uplift, Institute of Tibetan Plateau Research, CAS, Beijing 100085, China.
Jinbo
J
Zan