Composition and deformation patterns of the caprock on salt extrusions in southern Iran - Field study on the Karmostaj and Siah Taq diapirs

0546423 - GFÚ 2022 RIV GB eng J - Článek v odborném periodiku
Závada, Prokop - Bruthans, J. - Adineh, Sadegh - Warsitzka, Michael - Zare, D.
Composition and deformation patterns of the caprock on salt extrusions in southern Iran - Field study on the Karmostaj and Siah Taq diapirs.
Journal of Structural Geology. Roč. 151, October (2021), č. článku 104422. ISSN 0191-8141. E-ISSN 1873-1201
Grant CEP: GA ČR(CZ) GC20-18647J
Institucionální podpora: RVO:67985530
Klíčová slova: caprock breccia * fluid overpressure * salt diapir * salt extrusion * salt glacier * tectonic compression * Zagros fold and thrust belt
Obor OECD: Geology
Impakt faktor: 3.366, rok: 2021
Způsob publikování: Omezený přístup
https://www.sciencedirect.com/science/article/abs/pii/S0191814121001462

Two iconic salt diapirs in the Zagros Mountains in Iran – Karmostaj (Gach) and Siah Taq – are regarded as world-class examples of salt extrusions and are frequently called salt glaciers. However, our field survey revealed that their glacier-like parts are formed by thick, variegated and deformed caprock, only locally mixed with salt. Caprock is a layer of insoluble residuum that consists primarily of dissolution breccia and gypsum surrounding blocks of non-halite lithologies of the original evaporite sequence. Deformation within the caprock was accommodated primarily by shearing along gypsum-rich zones (gypsum mylonites) that surround subdomains of dissolution breccia and folded and fragmented blocks of carbonates and siliciclastics. Ductile flow in these mylonite shear zones was accommodated by pressure solution-precipitation creep of the lath-shaped gypsum grains. The ductile shearing of gypsum was locally accompanied by increased fluid-pore pressure driven fracturing of the surrounding lithologies. Since the subsurface shape of the salt diapirs is unknown, we present three hypothetical scenarios trying to explain the extrusion process of the studied diapirs and the associated deformation history of their caprocks. The diapiric structures represent either, 1) the remnants of degraded paleoglaciers, 2) advancing salt extrusions, or 3) only slightly reactivated, wide diapirs. To test these hypothetical scenarios, a geophysical survey is required to gain insights into the subsurface structures of the exposed diapirs and salt sheets.
Trvalý link: http://hdl.handle.net/11104/0322939