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Li K.,Xian Institute of Geology and Mineral Resources | Zhang Z.-W.,Xian Institute of Geology and Mineral Resources | Gao Y.-B.,Xian Institute of Geology and Mineral Resources | Guo Z.-P.,Xian Institute of Geology and Mineral Resources | And 4 more authors.
Northwestern Geology | Year: 2012

Shajia Cu-Ni ore-bearing basic complex is one of the intrusive rocks in Hualong basic-ultrabasic rocks belt, it is small scale, weak lithological zoning. Orebody are lenticular in the intrusion, and norite is the main host rock for the Cu-Ni ores. The analysis on rock geochemistry indicate that the intrusive is calcalkaline, iron series, rich in LREE, depleted in high field strength elements such as Nb, Ta. The analysis on the sulfide display that the initial 187Os/188Os ratios are from 0. 346 9 to 0. 407 1, the γos values are from 180 to 228, which suggest that abundant crustal material was mixed with the magma, and the content of crust-derived Os was estimated to >30%. The contamination by crustal material probably played an important role in triggering the sulfide saturation and segregation.

Field survey and geochemical study indicate that volcanic rocks of Aletai Formation, formed during Middle Devonian, outcropped in Fuyun county, Kalamanzhe area at the south margin of Altay Orogenic Belt. It generally consists of basalts and rhyolites, which are typical rock assemblages of bimodal volcanic rocks. Basaltic rocks are usually altered into albite-actinolite schist and epidote-tremolite schist, which belong to tholeiite series with low SiO 2, K2O content, and high Ti content. Its REE distribution pattern is flat-type with LREE slightly enriched. Without any obvious Eu anomaly (δEu = 0. 92-1. 08) , basalt is rich in Th and U, with an Nb negative anomaly. In comparison, the rhyolitic rocks belong to the calc-alkaline series with high SiO2 and low K2O, which are the agpaitic type. The REE distribution pattern goes rightward with an Eu negative anomaly (δEu=0. 29-0. 58). The MORB-normalized spider diagram shows evident enrichment in Th, U, La, Ce and Hf and loss in Sr, Nb, Ta, Zr, P and Ti. In terms of REE and trace elements characteristics, there are prominent differences between the basalts and rhyolites, showing that the rhyolites may derive from different degrees of partial melt in the mafic lower crust rather than the fractional crystallization of the basic magma. Whereas, the basalts may derive from partial melt of depleted mantle which was altered by subduction fluid. Geochemical researches of the bimodal rocks reveal that the rocks have geochemical features of both OIB and arc-island, but combined with the regional geological setting, kalamanzhe bimodal volcanics are probably the products of island-arc rifts, and belongs to mature island arc instead of the back-arc basin.

Liu M.,China University of Geosciences | Liu M.,Chinese Academy of Geological Sciences | Zhang Z.H.,Chinese Academy of Geological Sciences | Xiang J.F.,Chinese Academy of Geological Sciences | And 2 more authors.
Acta Petrologica Sinica | Year: 2014

The Daheishan tungsten deposit related to the biotite monzonitic granite from Baokuhe plutons locates at the Caledonian orogeny of Qilian Mountains. LA-ICP-MS U-Pb dating of zircons shows that the formation age of biotite monzonitic granite is 450.2 ± 2.8Ma, indicating that the pluton was formed at Caledonian magmatic-thermal event. Geochemical data reveal that the biotite monzonitic granite from Baokuhe plutons is rich in silicon (73.03% ∼ 74.18%), alkalis (K2O/Na2O= 1.13-1.94, K2O+ Na2O = 7.25% ∼ 8.51%) and is peraluminous (A/CNK = 1.04 ∼ 1.12). The biotite monzonitic granites from Baokuhe peraluminous plutons should be high potassic calc-alkaline granite. P2O5 content of the granites is low, and shows a trend of decrease with the increase of SiO 2 content. The content of rare earth element is low. Chondrite-nornalized REE patterns are right-inclined and display significant negative Eu anomalies. Differentiation of LREE is strong, and that of HREE is weak. Based on spider diagram of trace elements, Th, U, Pb, Zr, Hf are obviously positive anormaly, and Ba, Sr, Ta, Nb, P, Ti are negative anormaly. It suggests that it is an I-type granite. Combined with the tectonic evolution of the North Qilian, we suggest that the biotite monzonitic granite from Baokuhe plutons formed in the active continental margin, and the magmas were derived from the melting of crustal rocks, followed by crystal fractionation.

Yang Y.-Q.,Jilin University | Li B.-L.,Jilin University | Xu Q.-L.,Jilin University | Zhang B.-S.,Xian Institute of Geological and Mineral Exploration
Northwestern Geology | Year: 2013

Aikengdelesite is the first found porphyry molybdenum (copper) deposit in Eastern Kunlun for the past years and the degree of geological work and research for the deposit is quite low. The deposit lies to the Eastern Kunlun southern composite accretion belt. The hosted rocks are diorite, monzonitic granite, granite porphyry, medium-fine grain granite and volcanic rocks and sedimentary rocks of Hongshuichuan Group. In this paper, we present zircon U-Pb age data of monzonitic granite using laser ablation ICP-MS technique. The zircons of granite are mainly euhedral and hypidiomorphic texture, have clear ring and high Th/U ratio (0.83~1.47, average 1.15) which belong to the typical magmatic zircons. The results show that the intrusion mainly comes from late Hercynian but not late Indosinian period with the 206Pb/238U average weighted age of (268.7 ± 1.6) Ma (MSWD = 0.24) and concordant age of (268.5 ± 0.83) Ma (MSWD = 0.051). Comprehensive analysis reveals that the research area has entered into oceanic crust subduction stage in 268 Ma±.

Liu X.L.,China University of Geosciences | Liu X.L.,Chinese Academy of Geological Sciences | Wang Y.T.,Chinese Academy of Geological Sciences | Hu Q.Q.,Chinese Academy of Geological Sciences | And 5 more authors.
Acta Petrologica Sinica | Year: 2014

The Chaima gold deposit is located on the northwest of the Fengtai ore concentration area in Shaanxi Province and 0.5 km west to the super-large Baguamiao gold deposit. They are similar in metallogenic geological environment and ore-control conditions. There are five ore-bearing zones in this deposit and their occurrence is controlled by lithology and tectonic. The ores are quartz-vein type and altered-rock type, in which the first is the main type. The gold mineralization of Chaima gold deposit could be divided into three stages: the early quartz-carbonate stage, the second and main quartz-carbonate-sulfide stage and the late quartz stage. In this paper, the Sm-Nd isotopic dating is carried out on the calcite and dolomite from the main stage, yielding an isochron age of 203.2 ± 1.6Ma, which shows that the deposit formed in Late Triassic. Combined with the previous research on the gold deposits, magmatite and tectonic movements of the area, we suggest that the Chaima gold deposit is an orogenic gold deposit formed after the collision of Qinling in Late Indosinian.

Chen Y.,China University of Geosciences | Tang D.,China University of Geosciences | Xu H.,China University of Geosciences | Tao S.,China University of Geosciences | And 3 more authors.
Journal of Natural Gas Science and Engineering | Year: 2015

Recently, significant progress has been made in coalbed methane (CBM) exploration and development in the eastern margin of the Ordos Basin. However, the physical characteristics of coal reservoirs have not yet been studied in detail, and the physical characteristics of different rank coals are quite different. This study aims to analyze the characteristics of pores and fractures in coal reservoirs and identify the effects of coal rank on the physical properties of reservoirs, using laboratory experiments such as scanning electron microscopy (SEM), optical microscopy, mercury intrusion, low temperature liquid nitrogen adsorption, nuclear magnetic resonance (NMR) and X-ray computed tomography (CT). The results show that in relatively low rank coals the genetic types of pores are generally plant tissue pores and intergranular pores, whereas gas pores occur and proliferate with increasing coal rank. The porosity of the coal samples is low, ranging from 2.7% to 6.3% and varying in a wavelike fashion as the coal rank increases. Pore size distribution analysis indicates that micropores (pore radius<10 nm) and transition pores (pore radius between 10 and 100 nm) dominate the pore space in coal with a large proportion (64.82%-91.50%), followed by macropores (pore radius>1000 nm, 5.35%-22.69%) and mesopores (pore radius between 100 and 1000 nm, 2.34%-14.16%). The proportions of macropores and mesopores decrease first with coal rank increasing (Ro<1.0%) and then almost maintain at lower levels, while micropores and transition pores vary inversely. Adsorption pores in coals include micropores, transition pores and parts of mesopores, with proportions of 2.64%-61.54%, 30.77%-72.72% and 7.65%-37.31%, respectively. The proportion of micropores decrease firstly and then increase with coal rank increasing (turning point at Ro = 1.58%) and transition pores vary inversely. Micro-fissures density is between 12 and 217 per 9 square centimeters, which decreases as the coal rank increases firstly (Ro<1.5%) and then increases rapidly. In the lower rank coals, the properties of fractures, mainly short fractures, are relatively poor; however, higher coal ranks are favorable for endogenetic fracture development. © 2015 Elsevier B.V.

Yang G.-H.,Xian Institute of Geological and Mineral Exploration | Yang G.-H.,China University of Geosciences | Zhang W.-B.,Xian Institute of Geological and Mineral Exploration | Guo Y.-F.,Xian Institute of Geological and Mineral Exploration | And 5 more authors.
Northwestern Geology | Year: 2014

Sikeshu granitic pluton is located in the North Tianshan suture zone, the biggest granitic body which intrudes the Yilianhabierga island arc belt, and has tectonic significance as one stitching pluton. Sikeshu pluton is composed of various types of rocks generally formed in three intrusive periods. In the first period, the pluton rocks are quartz diorite and granodiorite, while in the second period the major compositions are monzogranite and K-feldspar granite, and in the third period the pluton is made of granite porphyry. Noticeably, rocks occurred in the second intrusive period constitute the main body of the pluton. On the whole, the rocks are featured by high-K calc-alkaline characteristics, with SiO2 content varying between 57. 85 and 74. 28 wt. %, K2O content from 1.95 to 5.25 wt.%, and Na2O content from 3.00 to 4.50 wt.%. The total REE content is between 113.91×10-6 ppm and 169.47×10-6 ppm. In addition, the values of (La/Sm) N, (Gd/Yb) N and (La/Yb) N fluctuate from 1.77 to 3.16, 1.33 to 2.12, and 3.41 to 5.64 respectively, showing a right-inclined distribution pattern characterized by weakly negative Eu anomalies with δEu value from 0.37 to 0.82. Moreover, the rocks are enriched in Th, Zr, Hf and depleted in Nb, Ta and Eu. In terms of deformation environment, quartz diorite and granodiorite of the first period mainly fall into the volcanic arc area of the pre-collision to the post-collision stage; rocks of the second period, namely monzogranite and K-feld-spar granite, mainly formed in the post-collision stage; and graniteporphyry in the last period occurred in later orogenic stage. LA-ICP-MS zircon U-Pb dating results of quartz diorite, monzogranite and K-feldspar granite are 324.1±4.3 Ma, 314.9±4.1 Ma and 311.5±3.9 Ma. Considering the age of Bayingou ophiolite, which is 344±3.4 Ma according to previous researches, we can conclude that the suture zone of North Tianshan formed between 344 to 311.5 Ma and the major collision orogenic process took place from 324 to 311 Ma, and then the suture moved into the post-collision stage after 311 Ma. To some extent, the three intrusive rock units of Sikeshu granitic pluton may be representative products of three tectonic-magmatic stages, which are subduction, collision and intracontinental orogenic of North Tianshan orogenic belt.

Yang H.,Xian Institute of Geological and Mineral Exploration | Zhang K.,Xian Institute of Geological and Mineral Exploration | Ren H.-W.,Xian Institute of Geological and Mineral Exploration
Northwestern Geology | Year: 2014

When evaluating mineral project applications and preliminary survey reports, experts often come across obscure prospecting ideas or inappropriate prospecting methods. However, as the core of mineral exploration work, the two aspects are vitally important in overall planning. Guided by prior metallogenesis phenomenon and professional knowledge, experts give their advice and recommendations on a regional basis. Their major concern includes important steps such as geology information integration, prospecting information gathering, the choice of prospecting ideas and methods, projects scheduling, work arrangements, implementation and supervision. The crucial prospecting ideas, methods and arrangements are often determined by the region's unique geological background. Each kind of geology leads to specific characteristics and patterns of mineralization. In reality, researchers often fail to integrate different methods as geological, geophysical, geochemical or remote sensing, therefore unable to find prospecting clues by the metal- logenic regularity indicated in the gathered information. Based on long-term exploring experience, we are able to classify the prospecting ideas into 6 steps: nformation gathering and integration; information classification and processing; 3D simulation of prospecting information; identification of mineral position and characteristics, selection of appropriate physical and chemical methods for specimen; © selection of engineering verification methods; © correction of errors between scientific speculation and facts.

Zhang Z.-W.,Xian Institute of Geology and Mineral Resources | Li W.-Y.,Xian Institute of Geology and Mineral Resources | Gao Y.-B.,Xian Institute of Geology and Mineral Resources | Guo Z.-P.,Xian Institute of Geology and Mineral Resources | And 5 more authors.
Northwestern Geology | Year: 2012

Hualong, is located in the South Lajishan, has developed many small basic-ultrabasic intrusions, simultaneously, is a great important Ni-Cu metallogenic belt in South Qilian mountains, and formed Yulonggou, Lashuixia, Yaqu small scale magmatic Ni-Cu sulfide deposits that relationed closely with these small intrusions. It found that the small intrusions belong to iron series basic-ultrabasic complex in Hualong by the study on geological and geochemical characteristics, expressed as the intrusions with Cu-Ni sulpides develop an iron-enrichment trend, rare earth elements exhibit a LREE enrichment characteristics, and shows egative Eu anomalies The enrichment in large ion lithophile elements (LILE), depleteion in high field strength elements (HFSE) and the appearance of a negative Nb-Ta anomally indicate a chemical affinity to cal-alkaline rocks. Ore isotope study revealed that the Ni-Cu deposits had formed from crystallization and differentiation of the original magma, suffered from crustal contamination, and the participation of Si-rich material. Together with regional tectonic evolution and mineralization recognization, it suggests that the formation of rock and ore in Hualong were related closely to geological environment on subduction.

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