The concentrations of trace elements have been used as indirect proxy for detection of hydrocarbon microseepage. The long-term seepage of hydrocarbons, either as macro or micro-seepage, can set up nearsurface oxidation reduction zone that favors the development of a diverse array of chemical and mineralogical changes. Under the reducing environment the hydrocarbon seepage, the solubility of trace elements increases that transports, due to hydrodynamic flow in the soil leading to the movement of soluble elements towards the reducing area. This study compares the trace element concentrations with adsorbed soil gaseous hydrocarbons and explains the trace elements concentrations pertaining to the hydrocarbon micro seepages. Total 81 numbers of soil samples were collected from the depth range of 1-2.5 meters below the ground level from Southern part of the Cambay Basin.

The trace metals such as Chromium (Cr), Copper (Cu), Arsenic (As), Selenium (Se) and Antimony (Sb) in the soil samples were analyzed using Atomic Absorption Spectrometer. The analytical results show the varying range of concentrations as Cr (0 to 76ppm), Cu (59 to 168ppm), as (63 to 155ppm), Se (72 to 182ppm) and Sb (6 to 19ppm). It has been observed that the concentrations of these elements are more when they are compared with their normal concentrations in the soils. The analyses of adsorbed soil gases show the presence of high concentrations of methane (CH4) ranged between 2 to 290 ppb, and sum of concentrations of SC2+ (C2H6, C3H8 and n-C4H10) ranged between 7 to 118 ppb. The integrated approach of trace elements over adsorbed light gaseous hydrocarbon (SC2+) anomalies showed better understanding. The increased concentrations of trace metals, suggest a soil chemical change to a reducing environment, presumably due to the influence of hydrocarbon microseepage. This methodology could further integrated with other geo-scientific studies such as 3D Seismic studies which may evolve with the holistic picture of identification of hydrocarbon bearing formations within the exploration blocks and the frontier areas.