Quaternary celestine and gypsum extensional veins in a folded hypersaline lake infill. The Qaidam Basin, Western China

Franz Neubauer, Yongjiang Liu, Johann Genser, Andrea Brigitte Rieser, Gertrude Friedl, Xiaohong Ge, Martin Thoeni

Veröffentlichungen: Beitrag in FachzeitschriftArtikelPeer Reviewed

Abstract

The nonmarine, at present hypersaline Qaidam basin of Western China comprises a ca. 8-17 km thick sedimentary fill, which is dominated by Eocene to Recent clastic rocks. These successions were folded due to ongoing India-Eurasia convergence from late Miocene onwards until today. Shortening also resulted in enhanced fluid flow and precipitation of sulphate minerals in subvertical tension gashes, which are mainly filled by celestine and fibrous gypsum. The orientation of subvertical veins is similar over most parts of the western Qaidam basin and indicates NNE-SSW to N-S shortening (present-day coordinates) dissimilar to the NE-motion direction deduced from recent geodetic (GPS) data. In deeper stratigraphic levels of anticlinal cores, tension gashes composed of fibrous gypsum subparallel to bedding demonstrate fluid overpressure during their formation at a shallow structural level, below the conversion temperature of gypsum to anhydrite. We interpret all these veins as near-surface precipitates from sulphate-rich brines during an advanced stage of folding. The 87Sr/ 86Sr ratios of a synsedimentary celestine layer and a celestine vein at the abandoned Dafengshan mine are 0.711414 and 0.711418, respectively, and are similar to those from Oligocene and Miocene limestones (0.711578 to 0.711679). Although the source area is highly heterogeneous in composition, these data indicate, therefore, in accordance with previous observations on clastic rocks, only a very minor change in the average 87Sr/ 86Sr ratio of the source region from Oligocene to Quaternary times.

OriginalspracheEnglisch
Seiten (von - bis)81-91
Seitenumfang11
FachzeitschriftAustrian Journal of Earth Sciences
Jahrgang103
Ausgabenummer2
PublikationsstatusVeröffentlicht - 2010

ÖFOS 2012

  • 105105 Geochemie
  • 105123 Stratigraphie
  • 105118 Paläontologie

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