Two 40Ar/39Ar ages and six fission track ages from monzonite and the Jurassic-Cretaceous rocks provide new geochronologic constraints on the timing of uplifting events in the north margin of the Luxi (鲁西) rise, eastern China. 40Ar/39Ar age 111.1±2.4 and 111.2±2.5 Ma of biotite and K-feldspar sampled from the monzonite may record the cooling age at 300 and 150-300 ℃, respectively. Fission track ages of zircon and apatite from the monzonite changing from 75±7 to 40±3 Ma record the cooling age at 250 and 120 ℃, respectively. The apatite from the Jurassic-Cretaceous sandstone and volcanic rocks yielded a different T-t path. The results indicate that there are two phases 111-46.9 and 13.4 (6.5)-0 Ma of rapid uplifting happened to the north margin of the Luxi rise; the first one is a tilted uplift from north to south in Zibo (淄博) during 111-46.9 Ma and in the south in Mengshan (蒙山) during 70-40 Ma; the second one is a tilted uplift from south to north in Mengshan during 32-20 Ma, and in turn in Taishan (泰山) and Zibo during 23-20 and 13.4-0 or 6.5-0 Ma, respectively. The aging coincidence between magmatism and tectonic uplifting implies there are two phases of uplifting induced by large scale extension and lithospheric thinning.
87Sr/86Sr,δ18O andδ13C ratios of calcite,dolomite,gypsum filling vugs and fissures in marine carbonates and their host rocks from the Sinian to the middle Triassic,are employed to trace the possible source and migration path of key fluids related to development of hydrocarbon,hydrocarbon preservation condition are then discussed further.Comprehensive research,based on the paleo-fluid,the property of formation water and the deformation intensity etc.,indicates that the preservation conditionsin the Shizhu synclinorium zone and Fangdoushan anticlinorium zone are the most predominant in the central Yangtze.Three sets of fluid systems in the Shizhu synclinorium zone are identified.Little fluid exchange occurs between the upper-middle fluid system and the lower fluid system,so two independent preservation units have developed.Both the Permian and the Triassic in the upper preservation unitsand the Dengying Formation of the Sinian and the lower Cambrian in the lower preservation units havegood preservation conditions.The preservation condition in the lower association(Z-S)located in the Huaguoping synclinorium zone in the western Hubei and Hunan is better than that in other tectonic units,where the fluids in the lower association migrated vertically across strata when the fluid isolating intervalswere destroyed,the regional seals are absent and the conditions for the preservation of hydrocarbon accumulations are totally destroyed.The preservation condition is increasingly more favorable from the western Jiangxi and Hunan to the western Hubei&eastern Chongqing on the whole.
Wang GuozhiXu GuoshengYuan HaifengHu XiaofengZou Can
