Abstract:Dabashan salient, located in the southern margin of the Qinling orogenic belt, has attracted much attention by its remarkable bow shaped geometry. The mechanics of the salient has long been discussed and several models have been proposed. However, these models can not account for the forming of a series of specific characteristics in the Dabashan structural belt. Recently, some researchers’works have revealed that the maximum horizental principal stress field is radial. Using the numerical modelling method, the displacement field and stress field during intra continental orogeny are modelled in the article. And the formation mechanism of the Dabashan salient is discussed. The numerical modelling results show that the pre existing salient shaped boundary originated in extensional setting and a pair of indenters in the front control the trajectory of the maximum horizontal principal stress during intra continental orogeny. Considering the background and previous analogue modelling results by the author, décollement is also considered to be a key role in the process. The Dabashan salient resulted mainly from pre existing salient shaped boundary formed in extensional setting, a pair of indenters in the front and lower décollement.

Abstract:The southeastern Yunnan area is the convergent plaace of Yantze, Cathaysia, Indo China blocks. The Babu opholite is considered a remnant of the Youjiang oceanic crust, one branch of Paleo Tethys. This study conducted an investigation using geological mapping, rock association, geochemistry and geochronology. Results shows that the Babu ophiolite has a relatively complete association: mantle peridotite, cumulate gabbro, diabase wall groups, pillow lava and radiolarian silicalite. But the Babu ophiolite is an allochthonousnappe superimposed onto Triassic turbidite deposit. Mantle peridotites consist mainly of harzburgite, and lavas and dikes are low K tholeiitic basaltic rocks, with REE and trace elements similar to N MORB. The typical trace element ratios such as Ti/V=20~50, Nb/Yb Th/Yb show that they were likely derived from DMM source. The observations suggest a MOR type ophiolite. SHRIMP U Pb age of zircons from amphibolites is 272±8Ma（n=11, MSWD = 0.54）, indicating a late Early Permian epoch. Considering late Paleozoic basic magmatism and sedimentary evolution of southwest Yangtze block, we proposed that the Babu ophiolite represents the residual oceanic crust of Youjiang basin during strong spreading in early Permian.

Abstract:In this study，we carried out a comprehensive research using zircon U Pb dating，petrogeochemistry and Sr Nd Pb Hf isotope analysis on the Xinxian granitic batholith to investigate its age, petrogensis, rock source and geochemical dynamic background. Analysis shows that the Xinxian granitic batholith has a zircon 238U 206Pb age of 125.5±1.5 Ma. Whole rock chemical compositions are characterized by high silica and alkali contents, lower values in Mg, Fe and Ca. The granites are enriched in light REE and large ion lithophile elements (Rb, K, Th, U) and Pb, but depleted in heavy REE, high field strength elements (Nb, Ta, and Ti ), Sr, and Ba. Isotopic analyses of the Xinxian granitic batholith yieldedinitial Sr ratios (87Sr/86Sr)i ranging from 0.706949 to 0.707086, low initial Pb isotopic ratios ［(206Pb/204Pb)i=16.611~17.152，(207Pb/204Pb)i=15.304~15.432，(208Pb/204Pb)i=37.316~38.702］, as well as low εNd(t) values (-13.65 ~ -13.51) and old Nd model ages (tDM2=2.12~2.13 Ga). Zircon has low εHf(t) values (-22.92~ -19.40) and old Hf model ages (tDM2=2.39~2.61 Ga). Based on the results of the whole rock geochemistry, geochronology and isotopic compositions, it can be concluded that the Xinxian granitic batholith belongs to a high K calc alkaline fractionated I type granite, which resulted from partial melting of the lower crust of Yangtze Block which probably consists of Neoproterozoic TTG like magmatic rocks at the northern margin of the Yangtze Block under a non thickened lower crust setting (<35 km).

Abstract:There are plenty of Late Paleozoic Mesozoic plutons outcropped in the southern margin of the eastern part of the East Kunlun Orogenic Belt, and their genesis and features of source region have long been the hot topic among geologists. This study carried out the detailed investigation over petrography, LA ICP MS zircon U Pb chronology and litho geochemical characteristics for the Helegang Xilikete plutons in the area. The results show that the plutons are characteristic of high Sr/Y and La/Yb ratios, high Na2O and Sr contents, apparent differentiation between LREE and HREE, slight positive and negative anomalies of Eu, and low contents of Yb and Y. All this features indicate that the plutons are similar to adakitic rocks. The rocks are classified to metaluminous or weak peraluminous high K calc alkali granitoid and enriched in LILE and depleted in HFSE, with high Mg# and Cr, Ni in content, and Nb/Ta value similar to that of continental crust. In addition, the rocks contain a lot of mafic enclaves and dark micro grained enclaves indicate they were the product of underplating of basaltic magma into lower crust. The zircon isotopic age of the plutons is about （225±5）Ma, representing their forming age. In combination with geochemical features, the age may imply that the eastern part of East Kunlun Orogenic Belt stayed in the transitional period from collision to post collision at that time.

Abstract:There are a lot of Permian igneous rocks which are widely distributed in Tarim Basin. Some researchers have done a lot of research on Permian volcanic rocks, but the results are not very perfect because of the limitations of outcrops, drilling and aeromagnetic data. However, with the progress of oil exploration in Tarim oil field in recent years, much more logging and seismic data is available, which makes the distribution of basalt in the Tarim Basin much more pefect. In this paper the distribution of Permian basalt in the central Tarim area is redefined through the comprehensive study of outcrops, drilling, logging, 2D seismic interpretation, especially the new approach based on down hole logging data interpretation, which improvs the much wider distribution of the basalt in Tarim Basin and is very important for the further research on the spacial distribution of the basalt in the hole basin.

Abstract:Located in the northeastern corner of the Tibetan Plateau, the Sikouzi section deposits huge thick Cenozoic strata whose provenancial analysis provides the exceptional opportunity to testify the deformational processes in the northeast Tibetan Plateau. Here, the single grain detrial zircon U Pb ages and Hf isotopic compositions are used to trace the source variation of the 27~4 Ma strata based on the Magnetostragraphy from the Sikouzi section. Most of the U Pb ages from 27~12 Ma samples concentrate within the intervals of 200~470 Ma (clustering around two peak ages of 230 Ma and 440 Ma), 1600~1890 Ma, 2100~2450 Ma. In contrast to the 27~12 Ma samples, 7 Ma sample has one more detrital zircon age peak of 720~980 Ma, and zircons from the sample with age of 4 Ma is dominated by U Pb ages in range of 200~490 Ma. In the samples collected from the Sikouzi Section, the 1600~1890 Ma and 2100~2450 Ma zircons mainly have positive εHf(t) values, the 720~980 Ma zircons have positive εHf(t) values ranging from -15.1~-1.7, and the 200~470 Ma zircons have εHf(t) values of -11.2 to 12.5. Comparing these with neighboring tectonic units, we found that zircon populations at 1600~1890 Ma, 2100~2450 Ma probably were drained from west margin of Ordos block, the 720~980 Ma zircons have their affinity to the Xihuashan and Nanhuashan and zircons at 200~470 Ma may come from west Liupanshan. The results of zircon source trace suggest that the southern Liupanshan probably initiate uplift at ~27 Ma and late Miocene deformation and uplift in this region may related to reactivation of Haiyuan Liupansh fault system.

Abstract:The Shabaosi gold deposit is only a large gold deposit in the northern Great Xing’an Range. Basing on quartz 40Ar/39Ar dating (crushing in vacuum and stepwise heating on crushed powders), we firstly obtained the ore forming age of the Shabaosi gold deposit. The crushing experiment yielded an isochron age of 130.1±1.3 Ma for primary fluid inclusions of quartz veins. The40Ar/39Ar dating by heating quartz power yielded an isochron age of 133.1±3.5 Ma for the microcrystal potash feldspars in quartz veins. The age of primary fluid inclusions in the quartz veins is coupled with that of the microcrystal potash feldspars and ~130 Ma may represent the forming age of Au bearing quartz veins. The Shabaosi deposit was formed in the Early Cretaceous in a tectonic transition setting of the post collisional regime of the Mongolia Okhotsk orogeny from compression to extension.

Abstract:The Waitoushan iron deposit is a typical deposit of banded iron formations (BIFs) in the Anshan Benxi area because of its large scale and widely distributed orebodies. We carried out a comparison research over the geochemical characteristics of iron poor and iron rich ores. The results reveal that both similarities and differences exist in two iron ores. The similarities of two ores show the the ores predominantly consist of TFe2O3 and SiO2, with minor other oxidates. Combined with the characteristics of trace and rare elements, it is suggested that the iron ores of the Waitoushan iron deposit belong to Algoma BIFs, but influenced by volcanic hydrothermal activity. But the total REE concentrations of iron ores is very low, but the PAAS normalized REE and Y diagram display depletion of LREE relative to HREE, distinct Eu positive anomalies and high Y/Ho ratios, and higher concentrations of ferromagnesian trace elements relatively, such as Cr, Co and Ni. Trace and REE elements analysis suggests that ore forming material may originate from deep sea hydrothermal fluid with seawater signatures. The differences of two ores show that Fe rich ores present distinct hydrothermal signatures, with K2O more than Na2O. In addition, trace elements composition is similar to granitization granite. Combined with field investigation, it can be inferred that the higher grade iron ore may be formed by leaner iron ore though activities of migmatization hydrothermal.

Abstract:Bolong porphyry copper deposit is the largest newly discovered deposit in the middle of Tibet plateau. Three stages of granodiorite porphyries were emplaced in the Bolong porphyry deposit, and the former two stages of granodiorite porphyries are mineralized porphyries. Zircon U Pb dating, bulk rock geochemical compositions and Sr Nd Hf isotopic compositions of these porphyries were analyzed. Zircon U Pb dating results shows that all these porphyries were intruded at 119~120Ma. The former two stages of granodiorite porphyries are enriched in light rare earth elements and large ion lithophile elements, and depleted in heavy earth elements and high field strength elements, with weak Eu anomalies, indicating that these granodiorite porphyries resemble arc magmas in composition. (87Sr/86Sr)i values of the first and the second stage of granodiorite porphyry are 0.70562~0.70711 and 0.70567~0.70850 respectively, with εNd(t) ranges within －4.0~－3.1 and －8.0~－2.4, εHf(t) varies within 2.5~6.9 and 3.3~6.9 respectively, suggesting that two stages of granodiorite porphyries were derived from juvenile lower crust. The third stage of granodiorite porphyry also shows arc magma affinities in composition, its higher εNd(t) (－0.7~－0.2) and εHf(t) (1.3~12.2) might suggest that the third stage of granodiorite porphyry was also generate from lower crust with more mantle derived materials. Bolong porphyry deposit were formed at the late stage of the northward subduction of the Bangong Lake Neo Tethyan Ocean, and the magmatic activity in the Bolong deposit should have close relationship with oceanic subduction, melt generated from subducted oceanic crust and subarc mantle wedge was upwelled, which might triggered partial melting of juvenile lower crust and formed the Bolong porphyry copper deposit. imply that the southern Qiangtang terrane should be thickened at 120Ma.

Abstract:To objectively evaluate shale gas exploration potential in the Lower Cambrian Niutitang Formation, northwestern Hunan, reservoir conditions of shale gas were investigated by means of X ray diffraction (XRD), scanning electron microscopy (SEM) and scanning probe microscopy (SPM) and so on. XRD analysis results suggest that brittle mineral contents range from 53.8 percent to 98.1 percent, with an average content of 77.9 percent. High value zones of brittleness mineral contents are mainly distributed in the Zhangjiajie Ganziping, Sancha and the surrounding areas. High magnification SEM analysis results indicate that there exist five kinds of pores and fractures, including residual primary pores, organic micropores, dissolution pores in unstable minerals, interlayer microfracture in minerals, as well as tectonic fractures. Of which structural fractures, organic micropores, dissolution pores in unstable minerals are the main constituents. SPM analysis results suggest that honeycomb organic matters distributed mostly in strip shaped and disperse states are rich in the mud shale of Lower Cambrian Niutitang Formation, northwestern Hunan, with nanoscopic porosities well developed in organic matters. Test results of Ultrapore 200 helium porosimeter show that porosity of mud shale is low, with a range from 0.6 percent to 11.7 percent (an average content of 4.6 percent) and the dominant factor of porosity is structural fractures, followed by TOC contents and feldspar contents. Test results of ULTRA PERMTM200 permeameter show that permeability of mud shale is relatively low, ranging from 0.002mD to 0.06mD (an average content of 0.014mD) and the dominant factor of permeability is structural fractures, followed by interlayer microfracture in minerals. Isothermal adsorption experimental results show that mud shale of Lower Cambrian Niutitang Formation had good adsorbability and TOC content may be the dominant factor to affect the mud shale.

Abstract:Fushan Sag is in the Beibuwan Basin is enriched in hydrocarbon. The third member of Liushagang Formation is currently an important reservoir in the northern part of the Huadong Beilian area. Its reservior lithology contains sandy conglomerate, gravel sandstone and fine sandstone，which consist mainly of lithic sandstone and feldspar lithic sandstone．In petrology，the sandstones are characterized by high composional maturity，high textural maturity and higher cement．Sandstone reservoirs from the third members of Liushagang Formation，which porosity is 8.41% 12.14% and permeability is 0.224×10-3μm2~3.472×10-3μm2，belong to the medium low porosity and ultra low permeability reservoir．Study demonstrates that mechanical compaction is main cause of tight sandstone reservoir，dissolution in medium diagenesis “A” improved reservoir property．Due to the enclosed diagenetic enviroment，feldspar and debris were not dissoluted completely. Authigenic kaolinite, although low content, can improve reservoir physics effectively，and fill pores along with illite/smectite mixed layer, illite and chlorite. Thus their effect on the reservoir is limited．Precipitation of illite/smectite mixed layer，illite，chlorite，carbonate and phase Ⅱ quautz along the fluid channel or pores are the important fators to the tightness of reservoir.