AUTHOR=Zhao Jian , Dou Lirong 

TITLE=Discovery of Early Mesozoic Magmatism in the Northern Muglad Basin (Sudan): Assessment of Its Impacts on Basement Reservoir

JOURNAL=Frontiers in Earth Science

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.853082

DOI=10.3389/feart.2022.853082

ISSN=2296-6463

ABSTRACT=The exploration potential of basement rock, as a special type of unconventional oil&gas reservoir, is usually determined by its lithology, and evolution. The crystalline basement in the Central African Rift System (CARS), which has been confirmed as a good unconventional reservoir in the surrounding basins of Muglad area, has long been considered to consist of only Precambrian rocks. In this study, at least 5 Early Mesozoic igneous intrusions have been identified for the first time at the north margin of the Muglad Basin. Field and microscopy studies show that they are mainly intermediate-acid intrusive rocks, including granite, syenite, diorite, and monzonite. Their mineral composition consists of alkaline feldspar, plagioclase, quartz, and seldomly hornblende, biotite, and magnetite. The Cathodoluminescence (CL) images of zircons from these intrusions mostly show oscillatory zoning, a typical characteristic of magmatic zircons. And the Th/U ratios and REE patterns of the analyzed zircons also indicated their magmatic origins. A total of 210 zircon U-Pb ages from 5 samples were obtained using LA-ICP-MS. Their ages range from 195.0±6 to 225.0±3 Ma, belonging to Late Triassic-Early Jurassic. These results suggest that the Muglad basin’s basement is not uniform, as previously understood with only ancient Precambrian rocks. The older basement has been intruded and modified by Early Mesozoic magma as evidenced by our dating results. These magmatic events lead to the formation of the diverse Mesozoic igneous rocks in the Muglad Basin. However, these intrusions still formed earlier than the formation of the Muglad Basin (Early Cretaceous), therefore they became new constitute members of the previous crystalline basement. Together with the Precambrian basement rocks, they also have experienced prolonged weathering and fracturing as long as 65 ~ 95 Ma. During this complex process, the basement could become porous and permeable weathered layers or fractured zones, serving as a good unconventional reservoir.