Insights into Carboniferous subduction-related petroleum systems in the Central Asian Orogenic Belt (CAOB) from hydrocarbons in vein calcite cements, West Junggar, northwest China

Abstract

Large Carboniferous petroleum systems exist in the Central Asian Orogenic Belt (CAOB), including the South Caspian and Junggar basins. In this study, we investigated one such petroleum system in the range belt by analyzing hydrocarbons in vein cements in the Daerbute fault zone that cuts Carboniferous strata in West Junggar, northwest China. Our multiple analytical methods included conventional petrographic descriptions, fourier transform infrared (FTIR) spectroscopy, and time-of-flight secondary ion mass spectrometry (ToF-SIMS). The results show that light hydrocarbons (C1–C7) are present in the vein calcite cements, which are characterized by bright yellow–green fluorescence, FTIR functional groups (i.e., ν [CH3], ν[CC]arom, and ν [C–H]arom), aliphatic hydrocarbon-related ion segments (i.e., [CnH2n+1]+, [CnH2n-1]+, [CnH2n-2]+, and [CnH2n-3]+; n < 7), and aromatic hydrocarbon-related compounds (i.e., C2-benzenes, C3-benzenes, and naphthalene). These hydrocarbons were sourced mainly from highly mature Carboniferous source rocks, and the subduction-related heat flow promoted hydrocarbon generation. This study provides the first insights into a subduction-related Carboniferous petroleum system in the CAOB range systems, which has significance for further petroleum exploration in orogenic belts.