Time filter

Source Type

Yang L.-Q.,China University of Geosciences | Deng J.,China University of Geosciences | Guo L.-N.,China University of Geosciences | Wang Z.-L.,China University of Geosciences | And 2 more authors.
Ore Geology Reviews | Year: 2016

The Early Cretaceous Taishang gold deposit is the largest deposit in the Linglong goldfield, Jiaodong Peninsula, with a pre-mining endowment of 326. t of gold. It is hosted in the 165-150. Ma Linglong biotite granite and controlled by the NEE- to NE-trending Potouqing Fault near the northern end of the regional Zhaoping Fault system. Hydrothermal alteration is well developed in the footwall of the Potouqing Fault and is characterized by a narrow zone of sericitization, followed by a wider zone of silicification, and an even wider zone of potassic alteration. The main orebodies (No. I orebody) comprise disseminated and stockwork-veinlet systems, although about 5% of the resources are in larger quartz veins (No. II orebody). Four stages have been identified for both styles of mineralization, on the basis of cross-cutting relationships and mineralogical and textural characteristics: pyrite-quartz-sericite (stage 1), quartz-pyrite (stage 2), quartz-pyrite-base-metal-sulfide (stage 3) and quartz-carbonate (stage 4). Gold was mainly deposited in stages 2 and 3, with minor amounts in stage 1.Petrographical, microthermometric, and laser Raman spectroscopic studies on fluid-inclusion assemblages in quartz and calcite from the four stages reveal three types of primary fluid inclusions: type 1 H2O-rich aqueous-carbonic, type 2 CO2-rich aqueous-carbonic, and rare type 3 carbonic inclusions. Stage 1 quartz primary inclusions are only type 1 inclusions, with an estimated composition of 88% H2O, 10% CO2, 4.5 wt.% NaCl equiv., and 0.5% CH4, with trapping at ~336°C and ~1.7kbars. The gold-rich stages 2 and 3 from both orebodies typically contain primary fluid-inclusion assemblages with both type 1 and 2 inclusions, which show similar phase-transition temperatures and were trapped between 246° and 294°C. The stage 4 quartz and calcite contain only primary type 1 inclusions, which are estimated to have a composition of 93% H2O, 6.0% CO2, 3.6 wt.% NaCl equiv., and trace amount of CH4, and were trapped at temperatures of >236°C.The δ34S values of hydrothermal pyrite from the four stages have a narrow range from 4.5‰ to 8.0‰, and are within the ranges for whole-rock sulfides from the Archean Jiaodong Group, and magmatic pyrite from Mesozoic granitoid and intermediate-basic dikes. The δ18O values of hydrothermal quartz range mainly from 10.9 to 12.5‰ and remain constant for all four stages; calculated fluid δ18O values are 1.3-10.0‰. The δDwater values calculated from hydrothermal sericite range from -60 to -45‰. Considering the fluid inclusion compositions, δ18O and δD compositions of ore-forming fluids, and regional geological events, the most likely ultimate potential fluid and metal reservoirs would be the Paleo-Pacific oceanic slab and its overlying sediments, which were thrust below the high-grade metamorphic rocks of the Jiaodong Peninsula.The initial ore-forming fluids were medium-high temperature, CO2-rich, and low salinity H2O-CO2-NaCl±CH4 homogeneous fluids. Over the duration of the hydrothermal system, the fluid remained fairly consistent in P-T-X, although becoming slightly more water-rich during final post-ore activity. Fluid immiscibility occurred during stages 2 and 3 ore deposition at pressures that fluctuated strongly from 1700 to 580bars during hydrofracturing. The (HS)2 - ion was the most probable gold-transporting complex at Taishang. Wall-rock sulfidation and episodic pressure drops, with associated fluid unmixing and other chemical changes, were the two main mechanisms of ore deposition. © 2015 Elsevier B.V. Source

Xie H.Q.,Chinese Academy of Geological Sciences | Wan Y.S.,Chinese Academy of Geological Sciences | Wang S.,Shandong Institute of Geological Survey | Liu D.Y.,Chinese Academy of Geological Sciences | And 4 more authors.
Acta Petrologica Sinica | Year: 2013

∼2.5Ga and ∼ 1.9Ga metamorphic events are widely recorded all over the North China Craton, being important for understanding the formation and evolution of the craton. Eastern Shandong is located in the eastern North China Craton and contains metamorphic rocks with ca. 2.5Ga and ca. 1.9Ga metamorphic zircon ages. For further constraining the Early Precambrian tectono-thermal events in the area, we carried out detailed field observation and SHRIMP U-Pb zircon dating in a road cutting section near Tangezhuang, Laixi County, eastern Shandong. The outcrop consists of interlayered and folded trondhjemitic gneisses and amphibolites. The foliation of the rocks is completely parallel to each other and shows thin interlayer in strong deformation domain, suggesting that thin interlayers of different components cannot be considered as a fact that the protoliths are sedimentary in origin. SHRIMP U-Pb zircon dating yielded an age of 2496 ± 10Ma (MSWD =0.45) for magmatic zircons from a trondhjemitic gneiss sample (S1105), with metamorphic rims having ages of ca. 2.5Ga and ca. 1.9Ga. Two amphibolite samples (S1238 and S0812) contain metamorphic zircons with ages of 1842 ± 3Ma (MSWD = 1.6) and 1833 ± 13Ma (MSWD = 1.0), respectively, but no magmatic zircons have been identified. Combining with previous researches, we suggest that the Late Neoarchean metamorphism widespread over the whole Jiaodong terrane, leading to anatexis and recycling of older crust material, and the Late Paleoproterozoic metamorphism shows a zonal feature as a result of orogenesis. Source

Lv J.,Nanjing University | Liu Y.,Nanjing University | Zhang Z.,Shandong Normal University | Dai J.,Shandong Institute of Geological Survey
Journal of Hazardous Materials | Year: 2013

The knowledge about spatial variations of heavy metals in soils and their relationships with environmental factors is important for human impact assessment and soil management. Surface soils from Rizhao city, Eastern China with rapid urbanization and industrialization were analyzed for six key heavy metals and characterized by parent material and land use using GIS-based data. Factorial kriging analysis and stepwise multiple regression were applied to examine the scale-dependent relationships among heavy metals and to identify environmental factors affecting spatial variability at each spatial scale. Linear model of coregionalization fitting showed that spatial multi-scale variation of heavy metals in soils consisted of nugget effect, an exponential structure with the range of 12. km (short-range scale), as well as a spherical structure with the range of 36. km (long-range scale). The short-range variation of Cd, Pb and Zn were controlled by land use, with higher values in urban areas as well as cultivated land in mountain area, and were related to human influence; while parent material dominated the long structure variations of these elements. Spatial variations of Cr and Ni were associated with natural geochemical sources at short- and long-range scales. At both two scales, Hg dominated by land use, corresponded well to spatial distributions of urban areas, and was attributed to anthropic emissions and atmosphere deposition. © 2013 Elsevier B.V. Source

Jia Y.G.,Ocean University of China | Wu Q.,Ocean University of China | Shang H.,Shandong Institute of Geological Survey | Yang Z.N.,Ocean University of China | Shan H.X.,Ocean University of China
Bulletin of Engineering Geology and the Environment | Year: 2011

The effect of contamination by crude oil has been assessed using samples from hand dug trial pits in the Hai-gang region of the Yellow River Delta. In addition to electrical resistivity and in situ penetration tests, grain size analysis, Atterberg limits, compaction, direct shear test and a micro-structure scan were undertaken. The results show that contamination was in the shape of a plume and non-uniform to a depth of 1 m. The more heavily polluted soil had a higher clay particle content, liquid and plastic limit and compression coefficient. However, no notable correlations were found between oil contamination and shear strength parameters. © 2011 Springer-Verlag. Source

Lu J.,Nanjing University | Lu J.,Shandong Normal University | Zhang Z.,Shandong Normal University | Liu Y.,Nanjing University | And 3 more authors.
Acta Geographica Sinica | Year: 2012

A total of 445 surface soils samples were collected at the nodes of a 2×2 km grid from Rizhao City and analyzed for 10 heavy metals (As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb and Zn). Sources of heavy metals pollutant and the differences of contents among various land use types and parent material were revealed by multivariate analysis; meanwhile, spatial distribution of hazardous risk from heavy metals contamination was given by geostatistics based on GIS. The results are shown as follows. (1) The mean concentrations of As, Co, Cr and Cu were lower than the background values (BV) in eastern Shandong Province, respectively; but those of Cd, Hg, Mn, Ni, Pb and Zn exceeded the BV, especially for Cd and Hg (1.85 and 1.38 times of BV, respectively), indicating distinct accumulations of some heavy metals in soils of Rizhao City. (2) A total of 10 heavy metals could be classified as 4 Principal Components (PCs), including PCI (Co, Cr, Mn, Ni and Zn), PC2 (Cd, Pb), PC3 (As, Cu), and PC4 (Hg). PCI and PC3 were the factors dominated by natural sources, PC2 represented the factors from industrial, agricultural and traffic sources, and PC4 was contributed by industrial sources. Pb and Zn with a high load in different PCs might originate from the mixed sources including anthropogenic and natural sources. (3) There were significant differences in Cd and Hg contents among various land cover types with the highest level in urban areas. The concentrations of Co, Cr, Cu, Mn and Ni in the soils from weathered granite and metamorphic rock were all higher than those in the soils from alluvial and marine deposits. (4) The single element, elements integration and the corresponding PC presented similar spatial patterns of hazardous risk. The high risk regions with comprehensive assessment on all elements were located in densely-populated urban areas and western study area, which was attributed to the higher geological background in the western part and strong human interference in the eastern part. Source

Discover hidden collaborations