Spatial Combination of Paleoprovenance and Depositional Lobe of Mid-Lower Yanchang Formation in the Northwest of Ordos Basin

For determining the distribution pattern of the depositional system of Yanchang Formation in the northwest of Ordos basin, thes chose mid-lower Yanchang Formation and did a systematic research on the provenance and the characteristics of the mother rock by methods such as the analysis of rocks and minerals, heavy mineral analysis, paleocurrent survey, sand distribution system drawing and paleo-topogrphy reconstruction etc The results indicate that the study area is mainly affected by four sediment sources, which have favorable spatial combination with depositional system: Rujigou lobe which has the largest influence on the study area is controlled by the Alxa Ancient Land; Shigouyi lobe develops from the overthrust sheet of Daluo Mountain; Otog Qi lobe and Dingbian lobe are controlled by the sedimentary sources in the northeast of Ordos basin. The mother-rock properties of the four provenances are very different. The ones in the Alxa Ancient Land and in the overthrust sheet of Daluo Mountain mainly consist of metamorphic rocks, including some granite and sedimentary rocks. However, the ones in the northeast of Ordos basin are mianly made up of granite and metamorphic rocks. Provenance analysis is useful to reasonable deployment of oil and gas exploration.