Characteristics and genesis of leopard limestone of the Ordovician Majiagou Formation in Ordos Basin
Wang Qicong, Yan Zuo, Ning Bo, Shi Kun, Liu Jiawei, Li Baiqiang, Jin Chengguang
School of Earth Science and Engineering，Xi’an Shiyou University，Xi’an710065，Shaanxi; School of Earth Science and Engineering，Xi’an Shiyou University，Xi’an710065，Shaanxi
Based on the outcrops observation and survey, thin sections identification,geochemistry analysis and temperature measuring of fluid inclusions,we studied the lithofacies,geochemical characteristics and structural feature of the leopard limestone from the Members 4 and 6 of Ordovician Majiagou Formation(M4 & M6 intervals)in Ordos Basin. In the Jinsushan section of southern Ordos Basin,three parasequence sets are divided by the eustasy in the M6B interval. The two parasequence sets in the lower part are mainly composed of leopard limestone,in which the continuity and ordering degree of the dolomite mottle are enhanced in ascending order. The dolomite mottle is comprised of euhedral to semihedral dolomites, with the relatively high value of δ13C, relatively low value of δ18C and 87Sr/Sr86, lower concentration of Fe and Mn, and higher salinity ratio and inclusion homogenization temperature. The results show that the leopard limestone of M4 & M6 intervals was mainly formed at the burial stage during which with the increasing buried depth and formation temperature, the dolomitization occurred by the evaprative seawater in the boriny pore refluxed at low sea-level period.
Wang Qicong,Yan Zuo,Ning Bo et al. Characteristics and genesis of leopard limestone of the Ordovician Majiagou Formation in Ordos Basin[J]. JOPC, 2016, 18(1): 39-48.
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