Abstract:Abstract：The Shangyi basin is located in the west segment of the frontal basin group of the Mesozoic nearly E-W-striking Yanshan thrust belt, where voluminous coarse fragments were accumulated during the deposition of the Late Jurassic Tuchengzi Formation. The Tuchengzi Formation in the basin shows a pronounced lateral sedimentary facies change from coarse gravelly deposits in the north to silty deposits in the south, displaying typical characteristics of asymmetric facies belt distribution. In the early-middle stages of deposition of the Tuchengzi Formation, there generally occurred conglomeratic alluvial fans (including mudflow deposits), braided streams and flood-plains and/or dried lakes from north to south. In the late stage of deposition of the Tuchengzi Formation, sandy and gravelly braided-river deposits were predominant, possibly intercalated with sandy dune deposits with large-scale eolian cross-bedding. Metamorphic rocks and granitoid rocks are dominant clastic components of conglomerate, indicting that the provenance was mainly the "Inner Mongolian axis" to the north of the basin. The sedimentary fillings have the nature of syntectonic conglomerate. A series of imbricate thrusts are developed at the northern margin of the basin. Preliminary analysis of the coupling relation between the faults and basin shows that the structural load of the thrust on the northern margin was an important factor for controlling the formation and evolution of the basin. The middle and lower parts of the sedimentary facies series near the side of the thrust to the north have the coarsening-upward characteristics, probably implying that the process of deposition of the Tuchengzi Formation was controlled by progressive thrust loading and lithosphere flexuring. Based on the relations between the basin and its related faults to the north, south-fining clastic size change and south-thinning, wedge-shaped section of the sedimentary basin, it is inferred that the basin formed in the continental interior in a N-S subhorizontal compressional setting.

Abstract:Abstract：The regional geological survey at a scale of 1∶250000 in the Zhidoi area in the northern segment of the Sanjiang belt, Qinghai Province, suggests that the extensively exposed intrusive rocks in the area mainly formed in the Late Triassic. According to the single-zircon U-Pb dating, granodiorite and porphyritic monzogranite in the Bayan Har terrane in the northeast of the Zhidoi area have ages of 212.38±7.1 Ma and 196.8±0.3 Ma respectively, and quartz diorite in the Jinshajiang ophiolitic mélange zone in the southwest of the Zhidoi area has an age of 215.4±0.8 Ma. Based on the geology, petrology and geochemistry of the protons, combined with the characteristics of regional tectonic evolution, it may be preliminarily determined that: these late Indosinian-early Yanshanian granitoids formed in a post-collisional stage; the magma has the feature of multiple sources and its formation may be related to lithospheric delamination.

Abstract:Abstract：The Early Triassic Indosinian Xichahe and Wulong plutons were emplaced into metamorphic rocks of the Mesoproterozoic Fuping Group in the South Qinling. A few mafic enclaves, which have a clear or obscure boundary with the host granodiorite, occur in the southern part of the Wulong pluton. Intensive petrographical, geochemical and Sr-Nd isotope studies indicate that the two plutons show some adakitic affinities：they are both strongly depleted in Yb and Y and enriched in Sr and Ba with higher Sr/Y and Y/Yb ratios and weak negative Eu anomalies. These patterns suggest a feldspar-poor, garnet ± amphibole-rich fractionation mineral assemblage. The mafic enclaves have higher Mg (MgO=4.15-8.13%), Cr (14.8-371 μg/g) and Ni (20.0-224 μg/g), as well as higher LREE and LILE, with Nb/Ta ratios of 15.42-21.9. It is inferred that the underplated mantle magma was responsible for the generation of the mafic magmas. The two plutons have similar Sr and Nd isotopic compositions, with (87Sr/86Sr)i＝0.70445-0.70645, εNd=-1.50-3.62 and TDM=1.02-1.38 Ga. Based on the aforesaid study, combined with previous studies, the authors think that the underplating of mantle-derived magma to the crust-mantle boundary induced amphibole eclogite facies or granulite facies metamorphism and partial melting of the thickened lower crust, thus forming adakitic magma. The difference of the two plutons in contents of some trace elements was caused by different degrees of contamination with mantle materials, and their formation probably represents the breakoff of the subducted Mianlue oceanic slab during the Indosinian late-collisional orogenic stage in the Qinling area.

Abstract:Abstract：There are three types of Yanshanian mineralized granite distributed in Hunan. Major element geochemical analyses show the following：(1) Mineralized granites have a higher ratio of K2O/Na2O and display the features of the high-K, calc-alkaline shoshonite series. (2)The MC-type and early CM-type granites are poor in Si and alkalis (K+Na) and rich in Ca, Mg and Fe with a lower aluminum index (A/KNC) and a lower alkalinity ratio of KN/A, which indicates that those granites have the same characteristics as magnesian and ferruginous, para-aluminous, high-K calc-alkaline rocks, such as I-type granite. The lC-type and late CM-type granites are relatively rich in Si and alkalis and poor in Ca and Mg, belonging to the ferruginous, slightly peraluminous-peraluminous shoshonite series. Their ratios of FeOT/MgO are notably higher than those of I- and M-type granites and their higher FeOT values indicate that these granites are apparently distinguished from highly differentiated I-type granites, but generally, they show the features of S-type granites. (3)The higher percentages of F and Cl in mineralized granites indicate that the magma of Yanshanian mineralized granites evolved toward the peraluminous or peralkaline one. The increase in concentrations of the HFSE in the late-stage magma led to mineralization of multiple metals such as Cu, Pb, Zn and Sb in the early-stage MC- and CM-type granites and large-scale mineralization of Sn, W, Pb, Zn, Nb, Ta and LREE in the late-stage aluminous C-type and CM-type granites. (4)The formation of the mineralized granites is related with crust-mantle magma intermingling. The magma generating the MC-type and early-stage CM-type granites was sourced from magma intermingling, while the magmatic evolution of C-type and late-stage CM-type granites might also involve fractional crystallization.

Abstract:Abstract：Quaternary investigation, which serves the urban geological investigation and aims at constructing 3D geological structure, has great exploratory potential. Take Hangzhou City for example, the paper explores and summarizes the methods and technical specifications for the 3D Quaternary structure investigation in the plain region of the city with respect to Quaternary standard hole construction, collection, compilation, analysis and selection of a mass of borehole data, shallow seismic exploration and composite well logging, stratigraphic division of the Quaternary and hole profile correlation.

Abstract:Abstract：A noticeable deep overpressure system occurs below 4,400 m depth in the well Pen-1 West subbasin in the interior of the Junggar basin. Studies of the geological, well log and geophysical data in the area show the following：the overpressure interval consists mostly of alternating beds of sandstone and mudstone；the mudstone interval is mostly a few to more than ten meters thick with a porosity of <8% and has been fully compacted; the slurry density increases greatly, being far higher than 1.2 g/cm3; both the sandstone and mudstone intervals have higher acoustic transit time and lower resistivity, and the stack seismic velocities near the wells also have abnormally lower values; the top of the overpressure interval is irregular in shape and penetrates the bed and macroscopically usually in a certain depth range. Analysis indicates that the lack of compaction and coal beds are not the cause for the lower velocity in the overpressure interval and that hydrocarbon, especially natural gas, generation makes the greatest contribution to the present overpressure generation.

Abstract:Abstract：The tectonic activity in the Longmen Mountains exhibited notable phased changes in the Upper Triassic Xujiahean period. The deposition stages of the second and fourth members of the Xujiahe Formation coincided with the stages of thrusting in the Longmen Mountains. The depocenter and subsidence center of the western Sichuan foreland-like basin are located in the foredeep near the basin-margin thrust belt, and the reservoirs on both sides of the basin are well developed and their deposits are very asymmetric. As the downcutting erosion increased with enhancing tectonic activities in the Longmen Mountains orogen, the lowstand systems tract on the side of the basin-margin thrust is better developed, while the highstand systems tract is preserved incompletely because of later subaerial exposure and erosion. On the other hand, the side of the forebulge slope was marked by steady slow uplift and weak downcutting erosion, and so the lowstand systems tract is absent or not well developed and the highstand systems tract is better developed due to weaker erosion in the late stage. The deposition stages of the third and fifth members of the Xujiahe Formation coincided with the repose stage of thrusting in the Longmen Mountains. The depocenter and subsidence center of the western Sichuan foreland-like basin moved toward the forebulge；the deposits on both sides of the basin are less asymmetric, which are characterized by the development of regional caps and source rocks. The sequence filling patterns of the two stages are similar to those of the thrusting stages. However, their depositional sequences, especially the highstand systems tract, in the front of the orogen are completely preserved because of weaker tectonic erosion; whereas in the forebulge the sequences are relatively incomplete mainly owing to lack of supply of sediments and thus only the sediments near the maximum flooding surface are preserved.

Abstract:Abstract：Sequence stratigraphy has developed for over 40 years, but it was applied to continental basins in China only ten years ago. The integrated sequence stratigraphic framework for the entire stratigraphic succession has not been established in many basins such as the Huanghua depression. Based on previous research, proceeding from the principle of sequence division and through studies of the characteristics and identification indicators of different orders of sequences and system tract boundaries, the paper proposes a scheme of sequence division in the Huanghua depression and divides the Paleogene strata into 1 first-order sequence, 3 second-order sequences and 11 third-order sequences. Based on studies of typical sections, the authors propose that the abrupt change of the depositional slopes, resulting from the structural slope break zone or flexure slope break zone, has an important effect on the accommodation and sedimentation in the basin and that the structural slope break zone and flexure slope break zone control the development of the sequences and lowstand sand bodies. Two models for the relation between slope break zones and sequences have been constructed, and it is pointed out that the areas below the slope break zones are favorable zones for the deposition of lowstand sand bodies.

Abstract:Abstract：Nine key sequence boundaries in Block 2 in the interior of the Junggar basin are traced and ascertained and high-resolution sequence stratigraphic division of the Jurassic was carried out according to the change in sedimentary facies sequence, stacking patterns of parasequences and features of log curves and by using the knowledge of key slope break zones, identifying the basal boundaries of lowstand systems tracts and analyzing onlaps, downlaps and erosional truncations nearby. The study indicates that eight third-order sequences were distinguished in the well C1 area during deposition of the Second Member of the Lower Jurassic Badaowu Formation to Middle Jurassic Toutunhe Formation. Each sequence was characterized by a complete tripartite structure, including lowstand systems tracts (LST), transgressive systems tracts (TST) and highstand systems tracts (HST) from below upward, and 27 systems tracts, 56 parasequence sets and 118 parasequences were identified. The thickness of a single sequence is 105.6-176.8 m and averages 140.7 m；the thickness of a single parasequence set is 24.9 m on the average and the thickness of a single parasequence is 11.8 m on the average.

Abstract:Abstract：The Jiyang depression is an important exploration target of the Shengli oilfield. The subsurface paleotemperature was an important factor for affecting the formation and evolution of sedimentary basins and the determination of subsurface paleotemperatures has great significance for the study of the hydrocarbon generation history and entrapment history. There are many methods for the study of subsurface paleotemperatures, of which the use of “the past as the key to the present”and geothermometry are the main methods. In this study the crystallinity of authigenic illite and chemical composition of authigenic chlorite was used to analyze the Cenozoic paleogeothermal gradients in the study area. The study indicates that the Cenozoic paleogeothermal gradients in the Jiyang depression were 37.2-38.2°C/km. This understanding is of great significance for the study, exploration and evaluation of the petroleum geology of the Jiyang depression.

Abstract:Abstract：Ordovician source rocks are widespread and very thick in the southern Ordos basin marginal paleo-depression. Of these rocks, mudstone and muddy carbonate source rocks are 10-57.6 m and 19.5-285 m thick respectively. They have a high organic abundance with the total organic content (TOC) clustering at 0.15%-0.20%. Organic matter of the source rocks are mainly of type I and type II1. The Ordovician source rocks began to generate gas in the early part of the Late Triassic (which is equivalent to the period of deposition of the Yanchang Formation) and gas generation reached the peak stage at the end of the Late Triassic. Later, the rocks stopped generating gas because the study area began strong uplift from the Jurassic on. There is no gas potential in the mountainous area in the southern part of the Weibie uplift at the southern margin of the Ordos Basin because of poor conditions of gas preservation. However, in the northern part of the Weibie uplift and the southern part of the Yishan slope of the Ordos basin, the burial depth of the Ordovician generally exceeds 3000 m, the time for gas generation was long and there are good conditions for forming a good gas accumulation; so the two area are favourable exploration targets for exploring for the structural gas accumulation and structural-lithologic gas accumulation.

Abstract:Abstract：The Jinwozi gold deposit is an important gold deposit located in the eastern segment of the East Tianshan-Beishan gold deposit concentration region, Xinjiang. There are different views about its mineralization age and metallogenic mechanism. However, as the mineralization age directly affects the understanding of the metallogenic mechanism, highly precise 40Ar/39Ar dating of the gold deposit and the shear belt was performed. The results indicate that the Jinwozi gold deposit formed in the Early Triassic and was the early Indosinian product. The mineralization age is in good agreement with the activity epoch of the regional ductile shear zone in the eastern area of the East Tianshan.

Abstract:Abstract：The Paleogene and Neogene sediments in the Fenghuoshan basin include the continuously deposited early Eocene to early Oligocene Fenghuoshan Group and early Oligocene Yaxicuo Group in the lower part and their overlying early Miocene Wudaoliang Group. All the sandstone copper deposits in the Fenghuoshan area occur in gray (green) sandstone of the first formation of the Fenghuoshan Group. Three apatite samples collected from the ore-bearing and barren beds of the first formation of the Fenghuoshan Group yielded fission track ages of 22.5±2.3, 33.1±6.0 and 28.0±3.6 Ma respectively. Of these ages, the age of 33.1-28.0 Ma is the mineralization age of the sandstone copper deposits of the area, while the 22.5±2.3 Ma age is the age of the post-mineralization tectono-thermal event. The mineralization ages of the sandstone copper deposits are in the range of ages of deposition of their overlying early Oligocene Yaxicuo Group, indicating that the sandstone copper deposits are the product of compaction and dehydration of the early-stage sediments in the basin.

Abstract:Abstract：The Tongchang copper-gold polymetallic deposit is a typical deposit of the Tongchang ore field in the Mian-Lue-Yang metallogenic province in China. Based on the study of the geological characteristics of the deposit, the ore-forming process may be divided into the pneumatolyto-hydrothermal period and reworked hydrothermal period. The latter may be subdivided into the pyrite-arsenopyrite-calcite-quartz stage, polymetallic sulfide stage and pyrite-carbonate-quartz stage. It is especially the case with the Cu-Au-(Co) polymetallic quartz-carbonate orebody occurring in NE-trending schistose zones of the diorite, where metallic mineralization is featured by horizontal zoning: from east to west there appear Cu→Co-Cu (Au)→Cu→Au-Au mineralizations and their tectono-geochemical anomalies. Four types of fluid inclusion are developed: vapor-liquid inclusions, liquid inclusions, vapor inclusions and liquid CO2-bearing polyphase inclusions, of which the first two types are dominant. Medium- and low-temperature, medium-pressure, moderate-oxygen fugacity and nearly neutral ore fluid conditions are favorable to the formation of the reworked hydrothermal deposits. The ore fluids were derived from reworked water (heated seawater and precipitation), magmatic water and metamorphic water. From the early to late stages of the reworked hydrothermal period, the reworked water was more and more dominant. So the deposit is regarded as a reworked meso-and epithermal deposit.

Abstract:Abstract：The Shangzhuangping Pb-Zn-Ag deposit is one of the sulfide deposits found in the Erlangping Group in the North Qinling Mountains during the new round of land and resources survey. The tectonic setting, material source and genesis of the deposit are discussed by studying the trace element and REE geochemistry of ores, host rocks and barite rock and geological characteristics of the deposit. The study shows that: the chondrite-normalized REE patterns for ores and host rocks are right-inclined；the data points of ores plot in the same field as those of the host rocks in Cu-Pb-Zn discrimination diagram；Zn/(Zn+Pb) for ores of the Shangzhuangping deposit is similar to those for the Okinawa trench and Shangxiang kuroko-type ores but is different from those for sulfides in TAG and the EPR13°N region; ores display higher As, Sb and Pb and lower Cu, Cd and Se, which indicates that the ore elements of the deposit were derived from the country rocks meta-(quartz) keratophyre and meta-spilite generated by crust-mantle mixing but mainly crustal rocks. The trace element and REE geochemistry of ores, geology of the deposit and their close paragenetic relationship with hydrothermally deposited barite rocks and cherts suggest that the Shangzhuangping Pb-Zn-Ag deposit was formed by submarine hydrothermal exhalative petrogenesis and mineralization in the back-arc basin environment. Barite rock, chert and vertical and lateral deposit zoning are important criteria for looking and exploring for such Pb-Zn-Ag deposits.

Abstract:Abstract：The Yaojiaoling copper lead-zinc deposit in the Tongling ore deposit concentration area of the middle-lower Yangtze River Valley metallogenic belt is a large polymetallic deposit discovered in recent years during mineral reconnaissance. The ore deposit type is considered as an epithermal filling replacement-porphyry deposit related to the intrusion of the late Yanshanian cryptoexplosive porphyry, which is very different from two traditional mineralization models——skarn type and modified stratabound type——in this area. This discovery accounts for the diversity and complexity of the mineralization in the area and has great guiding significance for mineral exploration at depths in the Tongling ore deposit concentration area and even in the middle and lower Yangtze River Valley.

Abstract:Abstract：Spring waters of twenty-two springs at Jinfo Mountain, Chongqing, were sampled and their geochemical characteristics were studied in detail during July and September 2006. Field and laboratory measurements of the concentrations of major cations and anions and other physico-geochemical parameters in the spring waters show that the hydrochemical types of these springs are Ca-HCO3 and Ca and Mg-HCO3, and on that basis, combined with the geological and geomorphological characteristics of the springs, six spring groups may be identified and the significance of the spatial distribution of these spring groups are discussed. The authors calculated the saturation indexes of calcite, dolomite and gypsum in the springs, which can indicate the influences of the lithology of the strata, topography and residence time of groundwater on the water quality. The results show that the spring waters in the area mainly come from penetration of meteoric water, without mixture of groundwater from the deep aquifer. The geochemical characteristics and spatial distribution of the spring waters may well reflect the geology of the study area. This study may provide baseline data for the investigation of groundwater resources and protection of the environment in the Jinfo Mountain area.

Abstract:Abstract：On the basis of hydrogeological investigation of the Yarkant River drainage area, Xinjiang, the authors analyze the sources of groundwater recharge according to the variations of D, 18O and T values in different regions and at different depths, solve the problem that is difficult to solve with the traditional research approach and provide a new idea for the study of the origin and spatial distribution of groundwater in arid areas. The results indicate that：(1) the groundwater is not derived from direct infiltration of precipitation but from seepage recharge of surface water；(2) there are two independent groundwater circulation systems which receive the waters of the Yarkant River and Tiznap River respectively；(3) the origins of phreatic water and confined water are the same, belonging to a unified groundwater system；and (4) in the sloping plain area the groundwater runoff is strong and groundwater movement is mostly horizontal, while in the fine soil plain area, the groundwater runoff is sluggish with vertical evaporative movement predominating and the runoff direction is closely related to the flow direction of surface water.

Abstract:Abstract：This paper discusses in more detail the determination of objective weight-values in the comprehensive evaluation of mine environmental geological problems. It introduces the method of objectively determining the weight-values of the evaluation index by using the data of the mine environmental geological investigation database and the method determining the weight-values of the evaluation index by expert questionnaires. The two methods are compared and analyzed, and with the help of examples, the applicability and credibility of the methods of comprehensive evaluation by using the objective weighted values to evaluate mine environmental geological problems are dealt with in an attempt to lay a preliminary theoretical basis for carrying out mine environmental geological comprehensive evaluation in China and preparing maps.

Abstract:Abstract：Regional early warning is an important means for improving the consciousness of geohazard prevention and reduction and effectively mitigating the loss caused by geohazards. In the early-warning method of explicit statistics, the effect of coupling of multiple factors such as geo-environmental change and precipitation is considered, thus overcoming the limitation of the single critical rainfall criterion. Based on the explicit statistic theory on geohazard early warning, applied studies have been carried out in the southeast of China. Twelve geo-environmental factors such as rock and soil types and topographic relief are selected to analyze the relationship between the distribution of geohazards and geo-environmental factors by using the determinacy coefficient function (CF), and the geohazard potentiality parameter is selected as an index of the geo-environment and quantitative calculation is performed. The very day rainfall and previous cumulative rainfall in one rain process are selected as an index of rainfall excitation conditions. Finally, the multi-regression analysis is used to analyze the relationships of the geo-environmental factor, rain excitation conditions and geohazards. Then an explicit statistic early-warning model for geohazards is constructed. Take for example the early warning during the land striking of the typhoon "Pearl" on May 18, 2006, the authors check the forecasting model and prove that the principle and model of explicit statistics early warning are feasible and practicable.

Abstract:Abstract：Full investigation and comprehensive analysis have been conducted on the bank slope ecological geo-environment in the Jinsha River, Yalong River and Dadu River hydroelectric project areas and main problems in the eco-environmental geology and environmental evolution effect. On that basis and according to the classification assessment concept and principle, the authors have explored the concept and method of assessment of the effect of cascade hydropower development on the ecological geo-environment in the drainage basin, established an assessment system of the effect of cascade hydropower development on the ecological geo-environment, which consists dominantly of four major subsystems, namely, the assessment subsystem of slope (bank slope) stability, assessment subsystem of soil erosion and reservoir sedimentation, assessment subsystem of the eco-environmental evolution and subsystem of the influence of social economic development, initially established four major assessment index systems and discussed the assessment method and expression way of assessment results for discussion.