Fluid inclusion evidence for deep burial of the Tertiary accretionary wedge of the Carpathians |
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| Authors: | Vratislav Hurai Franti&#x;ek Marko Antoni K Tokarski Anna
wierczewska Júlia Kotulov Adrin Biro&#x; |
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| Institution: | Vratislav Hurai,Franti?ek Marko,Antoni K. Tokarski,Anna ?wierczewska,Júlia Kotulová,Adrián Biroň |
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| Abstract: | Hydrothermal quartz from mineralized joints of the Carpathian accretionary wedge contains immiscible aqueous, oil‐condensate, methane and carbon dioxide‐rich fluid inclusions. Distribution patterns of the inclusion trapping PT parameters point to a crack‐seal mechanism during upward and lateral migration of hot methane‐rich fluids from overpressured sediments at the base of the accretionary wedge. A simple equation is proposed to calculate depths from densities and trapping pressures of the buoyant inclusion fluids. In the Carpathian accretionary wedge, the paleofluid pressures of 52–306 MPa correspond to a 5‐ to 11‐km‐thick overburden. Prior to exhumation, thickness of the wedge must have attained 10–25 km, of which only c. 50% was preserved until recently. Anomalously high methane densities (up to 0.43 g cm?3) recorded in the lowermost nappe sheets are provisionally interpreted as a result of supralithostatic overpressure due to thermal cracking of oil and kerogen to methane and pyrobitumen at temperatures above 200 °C. |
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