Geochemical exploration using surveys of spring water, hydrocarbon and gas seepage, and geobotany for determining the surface extension of Abu-Jir Fault Zone in Iraq: A new way for determining geometrical shapes of computational simulation models

The Abu-Jir Fault Zone (AJFZ) is a known fault zone and, as one of the typical structures in Iraq, extends NW-SE for a considerable distance on the western side of the Mesopotamian basin. The feature of this fault zone on the ground surface is mysterious and unclear. Surface extension evaluation of the fault zone requires the selection of valid parameters from among numerous geological factors. The present study focuses on the evidence of the existence of traces of the fault zone on the surface, such as springs, sites of hydrocarbon seepage, and geobotany, so as to employ them as tools in geochemical exploration for detecting the surface extension of the fault zone. For this purpose, direct and indirect geochemical methods including spring water survey (SWS), hydrocarbon accumulation and H2S gas survey (HAGS), and geobotanical survey (GS) were performed along the AJFZ. Hydrocarbon accumulations exist in many types of features. First, massive amounts of hydrocarbons ascend upward under high pressure piercing the gypsum of the Fatha Formation and exposed on the surface. Second, the hydrocarbon intrudes into the gypsum bed along the cleavage plane but is not exposed on the surface. Third, the light hydrocarbon ascends from the depth with the spring water and floats on the water surface. Anomaly in the distribution of hydrocarbon, total dissolved solid (TDS), H2S gas emission, abnormality in growth of palm trees (such as stem curvature and overturn, dwarfism), and the development of an isolated local aqueous environment around the springs along the AJFZ as well as computational simulation can be used to draw the geometrical shape of the fault zone on the surface. The surface extension of the AJFZ has been computed to be 467 km long with an average width of 48 km. This study has conclusively demonstrated the validity of the use of geochemical anomalies along with the computational simulation to estimate the dimensions of the fault zone.

► All waters of springs, well and lake are deep source of marine origin.
► Geochemical and geobotanical anomalies associate the hydrocarbons.
► Spring and lake waters ascended upward along the fault plain.
► Sites of springs, hydrocarbon, geobotany draw the surface extension of fault.
► Computational simulation is valid for determining the fault extension.