Geological Exploration Institute of Shandong Zhengyuan

Jinan, China

Geological Exploration Institute of Shandong Zhengyuan

Jinan, China
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Li X.-Y.,Ocean University of China | Li X.-Y.,CAS Qingdao Institute of Oceanology | Li S.-Z.,Ocean University of China | Li S.-Z.,CAS Qingdao Institute of Oceanology | And 10 more authors.
Journal of Asian Earth Sciences | Year: 2017

Early Cretaceous tectono-magmatic activity in the eastern North China Craton has long been linked to cratonic destruction, but no systematic investigations about the geodynamic processes have been performed. Early Cretaceous diabases, lamprophyres, andesites and dacites are distributed in the western Shandong Peninsula, and these rocks have a close relationship as they formed synchronously. Zircon U-Pb dating results show that the diabases and lamprophyres formed dykes or sills at 133-127Ma and that the andesites erupted at ∼125Ma. The diabases could be divided into high- and low-Mg# value groups. The high-Mg# (>60) diabases have lower SiO2 (48.44-54.68wt%) and higher MgO (7.41-19.30wt%) contents than the low-Mg# (<60) ones (SiO2: 52.90-56.41wt%; MgO: 2.70-4.37wt%). The lamprophyres (Mg# values of 58-70) exhibit low SiO2 (45.04-49.99wt%) and moderate MgO (4.77-9.87wt%) contents. The diabases and lamprophyres are enriched in large ion lithophile elements (e.g., Ba, Th and U) and light rare earth elements, are depleted in Nb and Ta, and feature negligible Eu anomalies. They have lower zircon εHf(t) values (-12 to -19) and whole-rock εNd(t) values (2 to -12), with (87Sr/86Sr)i ratios of 0.7066-0.7097. The andesites and dacites have intermediate SiO2 contents (60.10-64.95wt%), high Mg# values (56-65), high Sr (1005-1300ppm), and low Y (11.3-12.9ppm) contents, with high Sr/Y ratios (78-115), showing adakitic affinity. They have lower zircon εHf(t) (-12 to -26) and whole-rock εNd(t) (-9 to -13) values and high (87Sr/86Sr)i ratios (0.7109-0.7111). We suggest that the diabases and lamprophyres were derived from the partial melting of enriched lithospheric mantle, and the parental magmas of some of them had more contribution from the asthenosphere. The andesites and dacites were derived from the partial melting of delaminated thickened lower crust with addition of mantle material. Since the late Mesozoic, local delamination may have occurred beneath the Shandong Peninsula. During the Early Cretaceous, the rollback process of the Paleo-Pacific slab beneath the Shandong Peninsula could have facilitated delamination of the lithospheric mantle, and enhances the activity of trans-lithospheric faults. © 2017 Elsevier Ltd.


Pan Y.,China University of Geosciences | Yu B.,China University of Geosciences | Zhang B.,China University of Geosciences | Zhang B.,Geological Exploration Institute of Shandong Zhengyuan | Zhu G.,Petrochina
Journal of Earth Science | Year: 2017

The Ordovician of the Tazhong area in the Tarim Basin has suffered multi-cyclic hydrocarbon charging, making Tazhong a typical condensate gas district. In this paper, production and test data were gathered and a detailed comparison was conducted on the geology and the fluid distribution and characteristics between the eastern and western Tazhong area. Eastern and western regions exhibit significant differences in tectonic structure, fluid distribution, and physical-chemical properties of oil and gas. Compared with the eastern region, the western part has a greater development of discordogenic gas associated with strike-slip faults which, combined with the Tazhong No. 1 fault zone, control the fluid distribution. The eastern region is mainly controlled by the Tazhong No. 1 fault zone. Fluid have markedly homogeneous properties in the east, but are heterogeneous in the west. The origins of oil and gas are different between the east and the west. In the east, hydrocarbons are mainly from Ordovician source rocks and natural gas is mostly derived from kerogen pyrolysis. In the west, the hydrocarbons mainly originated from Cambrian source rocks, and the gas was mostly generated by crude oil cracking. In sum, the east region is dominated by primary condensate gas reservoirs, and the western region is dominated by secondary condensate gas reservoirs. Because of the different geological settings and fluid physical properties, differences in the condensate gas reservoirs in the eastern and the western Tazhong area have been analyzed, and appropriate formation mechanisms for condensate gas origins are established. © 2017, China University of Geosciences and Springer-Verlag Berlin Heidelberg.


Zhang B.,China University of Geosciences | Yang L.,China University of Geosciences | Huang S.,Jiaojia Gold Company | Liu Y.,China University of Geosciences | And 5 more authors.
Acta Petrologica Sinica | Year: 2014

Jiaodong Peninsula, the most important gold province in China, is an area with concentration occurrence of large-superlarge gold deposits, the proved reserves in Jiaodong Peninsula account for nearly 1/3 of the country's. Fracture zone altered type gold deposit is the most important deposit type which accounts for more than 90% of the proved gold reserves in Jiaodong Peninsula. Jiaojia gold deposit is named after "Jiaojia-type" fracture zone altered rock type gold deposit, large-scale sericite-quartz alteration zone (with the width of 20 ∼200m) and potassic alteration zone (with the width of 50 ∼300m) occur in the gold deposit. Altered rock type gold orebody mainly develops in the sericite-quartz alteration zone which is in the footwall of Jiaojia fault zone. Based on the detailed geologic observations in the field, this paper found out the alteration type and mineral assemblage of the Jiaojia gold deposit, collected different types of alteration rock samples scientifically, and conducted rock geochemistry element analysis which uses the method of the mass balance to discuss the regularity of elements migration in the hydrothermal alteration process and mechanism. Thereinto, potassic alteration occurs in the premineralization, potassic granite is usually as lumpy and breccia residual in the pyrite-sericite-quartz and sericite-quartz altered rock which is controlled by the secondary faults in the footwall of the Jiaojia fault, and the scale is controlled by the faults. The scale of sericite-quartz altered rock is the largest in the footwall of the Jiaojia fault with the width of 10 ∼ 200m, sericite-quartz altered zone controlled by secondary faults is relatively small, usually presenting as wide 0. 1 ∼ 1 m veins in the potassic granite, which indicates sericite-quartz alteration is later than potassic alteration. Compared with biotite granite, rocks from various alteration zones show high contents of K2O and low contents of A12O3, CaO and Na2O, but elements like Si, Fe, and Mg have different characteristics. Potassic granite are rich in K2O, while both sericite-quartz altered rock and pyrite-sericite-quartz altered rock are characterized with increasements of MgO and Fe2O3. During the process of potassic alteration, SiO2and K2O were added, indicating that the forming fluid is silicon-rich, alkaline and oxidation. In the process of alteration from potassic granite to pyrite-sericite-quartz altered rock, the Fe2O3increased obviously, which may be caused by the decomposement of biotite and other melanocratic minerals. Furthermore, sulfophilic elements like Au, Ag, As, Pb and Zn also increased significantly. Part of the gold may be derived from Linglong biotite granite. In the process of potassic alteration, the metasomatism between the wall rock and silicon-rich, alkaline and oxidation fluids, extracted gold in the form of high valence ion from wall rocks. To be specific, dispersed reduced gold (Au0) was activated to be oxidized (Au+, Au3+), and migrated with the fluids in the form of AuH3SiO4. In the process of sericite-quartz alteration, the descent of the content of SiO2induced the decomposement of AuH3SiO4. Fe2+and Fe3+were consumed to form the pyrites, which induced the deposition and enrichment of gold. Gold activate, migrate and deposit run through all these process.

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