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Zhang N.,Xinjiang Institute of Ecology and Geography | Zhang N.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | Zhou K.,Xinjiang Institute of Ecology and Geography | Zhou K.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology
Journal of Applied Remote Sensing | Year: 2017

Remote sensing technology plays a vital role in the initial stages of ore deposits exploration, with special significance in arid and semiarid regions. Advanced spaceborne thermal emission and reflection radiometer (ASTER) creates opportunities for geologists and many researchers to study the extraction of hydrothermal alterations of the porphyry copper and epithermal gold deposits. ASTER data were used to map distribution of hydrothermal alteration of deposits in the Baogutu region which is located in western Junggar, Xinjiang, China, including Baogutu II and Baogutu V deposits. Band ratio logical operator (BRLO), principal component analysis (PCA), mixture-tuned matched-filtering (MTMF), and constrained energy minimization (CEM) techniques were used for detailed hydrothermal alteration mapping. The alteration zones were identified using BRLO and PCA. The minerals subject to alteration were extracted by MTMF and CEM. The results were validated through field observation, spectral measurements, and petrographic studies. By comparing the extraction results and accuracy rates of four methods, CEM boasts the highest accuracy and identifies the altered minerals corresponding to three types of alterations at accuracy of over 80%. The identifying result of CEM method indicates that the prospect areas that were located in the southeast part of the Baogutu II rocks and in the southwest part of the Baogutu V rocks are valuable for further exploration. © 2017 Society of Photo-Optical Instrumentation Engineers (SPIE).

Sang M.,Xinjiang Institute of Ecology and Geography | Sang M.,University of Chinese Academy of Sciences | Sang M.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | Xiao W.,Xinjiang Institute of Ecology and Geography | And 8 more authors.
International Geology Review | Year: 2016

The exhumation and tectonic emplacement of eclogites and blueschists takes place in forearc accretionary complexes by either forearc- or backarc-directed extrusion, but few examples have been well analysed in detail. Here we present an example of oblique wedge extrusion of UHP/HP rocks in the Atbashi accretionary complex of the Kyrgyz South Tianshan. Our field mapping and structural analysis demonstrate that the Atbashi Eclogite–Blueschist Complex is situated in a complicated duplex formed by a northerly dextral transpression system and a southerly sinistral transtension system. The two major shear systems suggest that the Atbashi Complex was extruded obliquely southwestwards during eastward penetration of the southern tip of the Yili–Central Tianshan Arc of the Kazakhstan Orocline during the Late Triassic. Also, we report new zircon U–Pb metamorphic ages of four eclogites and one garnet-bearing quartz-schist from the Atbashi complex of 217–221 Ma and 223.9 Ma, respectively, suggesting that the main extrusion was later than previously proposed and that the final orogenesis was not completed until the Late Triassic. The HP/UHP rocks have an oblique plunge to the NE and extrusion took place southwestwards during escape tectonics along the South Tianshan accretionary wedge in the Late Triassic. Our work shows that the movement of HP/UHP rocks had a 3D style with an arc-parallel structure, and sheds light on earlier 2D models with either forearc- or backarc-directed extrusions, which indicates that more systematic structural and geochronological work is needed to characterize the accretionary tectonics of many orogens around the world. Our data on the timing of extrusion and emplacement of the Atbashi Eclogite–Blueschist Complex also help to resolve the long-standing controversy about the time of terminal orogeny of the Central Asian Orogenic Belt. © 2016 Informa UK Limited, trading as Taylor & Francis Group

Feng Q.,Xinjiang Institute of Ecology and Geography | Feng Q.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | Zhou K.,Xinjiang Institute of Ecology and Geography | Zhou K.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | And 2 more authors.
Scientia Geologica Sinica | Year: 2015

The eastern Junggar, located among the Altai, eastern Tianshan and Junggar Basin, is the key area to understand the tectonic evolution of the central Asian orogenic belt(also called North Asian orogenic region). Previous studies mostly focused on rock associations and geochemical characteristics of the eastern Junggar, but the structural deformations, specially the deformations in middle-small scale, were rarely involved. This study initially find that there are large amount of dark-colored mafic dykes emplaced in eastern Junggar, they were formed by mafic magma from the deep intruding into the earlier formed fractures in the host rocks. Dykes can provide both temporal and spatial constrains on the mechanism of structural fractures. In Hersai pluton, a granite pluton of Qiongheba arc in eastern Junggar, 874 segments of dark dykes are distinguished by high-resolution remote sensing interpretation and previous regional survey. The Hersai pluton was formed in Early Devonian and dykes were formed in Late Carboniferous to Early Permian. The majority of their strikes are NWW-SEE and minority strikes are NE-SW and NW-SE. Macroscopic deformations of the dykes reveal that the NWW-SEE trending dyke-fractures are extensional caused by NWW-SEE compression, the NE-SW dyke-fractures are compressional-dextral, and the NW-SE dyke-fractures are extensional-sinistral. Combined these dyke-fractures with different trending into consideration, they were caused by NWW-SEE regional compression. This study reveals that during the Late Devonian to the Early Carboniferous, Hersai pluton was compressed by NWW-SEE maximum principal stress and different groups of fractures were formed, which may be caused by intercontinental collision after termination of ocean basin. The occurrence of mafic dykes in the Late Carboniferous to the Early Permian may be caused by so-called post-collisional extensions. © 2015, Science Press. All right reserved.

Zhang N.,Xinjiang Institute of Ecology and Geography | Zhang N.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | Zhou K.,Xinjiang Institute of Ecology and Geography | Zhou K.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology
Journal of Intelligent and Fuzzy Systems | Year: 2015

Knowledge-and data-driven approaches are two major methods used to integrate various evidential maps for mineral prospectivity mapping (MPM). Geological maps, geochemical samples and data from known gold deposits were collected in the western Junggar area, Xinjiang Province. The geological and a spatial database for geological and mineral occurrences were constructed for the studied region. A weights-of-evidence model and a fuzzy logic model were employed for MPM, and the results were compared. Results indicate that favorable sedimentary rocks, fault density, fault distance and concentration of Au were the primary factors affecting Au mineralization. Arsenic (AS), Stibium (Sb), fault direction, quartz veins and intrusive rocks were secondary factors affecting Au mineralization. Conditional independence exerted a major influence on the weights-of-evidence model. However, posterior probability would be very high if the conditional independence was disregarded, which impaired results. Combining the quantification results provided by weights-of-evidence and the fuzzy membership values determined by expert knowledge, the mineral prospectivity mapping according to the fuzzy logic method was proved to be valid. For the study area, which had a large number of deposits, data-driven approaches for MPM are generally considered to be appropriate. However, if sufficient data are not collected, the knowledge-driven approaches, for example, the fuzzy logic method used in the present study, usually achieves a better result. © 2015 - IOS Press and the authors. All rights reserved.

Wu Y.-S.,Xinjiang Institute of Ecology and Geography | Wu Y.-S.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | Zhou K.-F.,Xinjiang Institute of Ecology and Geography | Zhou K.-F.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | And 3 more authors.
Ore Geology Reviews | Year: 2016

The giant Donggebi porphyry Mo deposit is located in the Jueluotage metallogenic belt of Eastern Tianshan, Xinjiang, Northwest China. Mo mineralization mainly occurs as numerous veinlets in the altered sandstone wall-rocks, with the development of potassic, phyllic, argillic and propylitic alteration assemblages outward from a buried porphyritic granite stock. Zircon crystals from the buried porphyritic granite yield a weighted average 206Pb/238U age of 236±2.2Ma (MSWD=1.2, 1σ, n=17), slightly older than the molybdenite Re-Os isotope ages of 231-234Ma, suggesting that the Donggebi porphyry Mo deposit was formed in the Triassic, post-collisional tectonism subsequent to termination of the Paleo-Asia Ocean. The samples from porphyritic granite show high contents of SiO2, K2O and Al2O3, low contents of TiO2, MgO and CaO, and peraluminous high-K calc-alkaline to shoshonite affinity, with obvious LREE enrichment and negative Eu anomalies. They have high initial 87Sr/86Sr ratios of 0.70618 to 0.70821, εNd(t) values of 0.60 to 1.62, and T DM2(Nd) ages of 0.88 to 0.96Ga. Their (206Pb/204Pb)t, (207Pb/204Pb)t and (208Pb/204Pb)t values are 17.122-18.577, 15.493-15.574, and 37.887-38.006, respectively. Zircons from the porphyritic granite yield εHf(t) values of -1.58 to 4.82, and T DM2(Hf) ages of 0.96-1.36Ga. These geochemical and isotopic data imply that the Donggebi porphyritic granite originated mainly from partial melting of lower continental crust derived from a depleted mantle. The Donggebi Mo deposit is unique based upon the crustal source for the causative porphyry, the distal position of mineralization, and the previously revealed CO2-rich ore-forming fluids, and thus belongs to the collisional- or Dabie-type porphyry deposits as exemplified by the Qiane'chong and Yaochong deposits in Dabie Shan, the Donggou deposit in Qinling Orogen, China. © 2016 Elsevier B.V.

Li N.,Xinjiang Institute of Ecology and Geography | Li N.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | Li N.,University of Aarhus | Pirajno F.,University of Western Australia
Ore Geology Reviews | Year: 2016

As one of the most important Mo provinces in the world, the Qinling Orogen is host to mainly Late Mesozoic (Late Jurassic-Early Cretaceous) porphyry Mo systems. Recently, additional Early Mesozoic (mainly Triassic plus minor Early Jurassic) Mo deposits have been identified, which occur as fault-controlled quartz veins or as carbonatite veins and as such, they are fundamentally different from the commonly observed porphyry systems. Furthermore, Early Mesozoic porphyry systems are also present but they are different from those of Late Mesozoic age. Thus, Early Mesozoic Mo systems not only offer a new and comprehensive view of the Mo metallogenesis, but also provide unique insight into the tectonic evolution of the Qinling Orogen taking into consideration the role of mineral deposits as ideal probes of the geodynamic evolution.The known Early Mesozoic Mo deposits in Qinling can be classified into three types based on their geological and geochemical features: porphyry, carbonatite, and orogenic systems. Porphyry Mo systems, including porphyry, porphyry-skarn and intrusion-related veins, are spatially and genetically associated with granitic porphyries. They display typical porphyry type alterations and are formed by magmatic water. Carbonatites are considered as mantle-derived igneous rocks, and Mo mineralization is associated with magmatic fluids. Orogenic Mo systems occur as fault-controlled quartz lodes, and the ore-forming fluids are medium-high temperature, CO2-rich metamorphic fluids. Spatially, Early Mesozoic porphyry Mo systems are concentrated in the western and middle part of the Qinling Orogen, whereas carbonatite veins and orogenic Mo systems are located in the northeastern part. Temporally, orogenic Mo deposits were the earliest (mainly between 220 and 250Ma), followed by carbonatite veins (mainly between 205 and 225Ma) and porphyry Mo systems (mainly between 190 and 205Ma). With some exceptions, there is generally a trend of decreasing deposit ages toward the western part of the orogen. Detailed comparison reveals that the Early Mesozoic porphyry Mo systems in the Qinling Orogen are different from the Late Mesozoic ones in terms of their economic importance, spatial distribution, ore-causative intrusions, hydrothermal alteration and the ore-forming fluids.To explain the above geological and geochemical features, the Triassic Qinling is considered as an active continental margin caused by the northward subduction of the Mian-Lue oceanic plate. A transition from continental arc to back-arc basin is suggested for the formation of Triassic orogenic and carbonatite vein Mo deposits, whereas continental arc is host to the Early Mesozoic porphyry Mo systems. © 2016.

Liu Y.,Xinjiang Institute of Ecology and Geography | Liu Y.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | Liu Y.,Wuhan University | Cheng Q.,Wuhan University | And 5 more authors.
Geochemical Journal | Year: 2016

Identification of underlying geochemical processes based on samples of different types such as stream sediments, soils, and water is important for a range of applications including mineral exploration, land use planning, and environmental assessment of both natural and anthropogenic factors. However, almost all geochemical compositions of these samples are subject two limitations: outliers and the data closure effect. In the present study, bivariate relationships between selected major elements are examined to illustrate their spurious correlation by using centered log ratio (clr) transformation. In addition, robust factor analysis (FA) and compositional data analysis are used to prevent the effect of outliers and to reduce the influence of data closure in the identification of geochemical processes. First, a k-means algorithm is applied to partition geochemical data into three clusters to enhance the interpretation of the geochemical data. Then, robust FA is applied to log ratio-transformed geochemical data. The first five factors are extracted on the basis of the scree plot of eigenvalues. The results indicate that robust FA applied to log ratio-transformed data can be used to effectively identify geochemical processes and to determine the extent of anthropogenic and natural influences such as mineralization, weathering and diagenesis, heavy metal accumulation or contamination, or a combination of these factors. Several geochemical processes are indicated by the first five factors, explained as follows: (a) F1 reflects granitic rocks and natural or industrial contamination by Cu, Ni, Sb, As, Cd, and Cr; (b) F2 reflects W polymetallic mineralization; (c) F3 reflects Au anomalies and heavy metal contamination by Zn, Cd, Mn, and Pb; (d) F4 reflects Mo and Au anomalies; and (e) F5 reflects Ag-W-Be-La mineralization and heavy metal contamination by Hg and Sb. Copyright © 2016 by The Geochemical Society of Japan.

Zhang N.,Xinjiang Institute of Ecology and Geography | Zhang N.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | Zhou K.,Xinjiang Institute of Ecology and Geography | Zhou K.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | And 2 more authors.
Xinan Shiyou Daxue Xuebao/Journal of Southwest Petroleum University | Year: 2016

Extraction of information in geochemical anomalies has long been geologists' concerns. In this paper, we use the collected 1:20 millions of geochemical data of the western Junggar area to analyze spatial variability of the Au elements, and interpolate it. By using the C-A model of fractal and the traditional method, we obtain different anomaly threshold values. We compare the method of extracting geochemical anomalies information based on the traditional method and fractal technique. The result proves that the spatial distribution of Au elements is characteristic of isotropic with medium correlation;the fractal method is better than the traditional one. Fractal technology and known gold deposits agree better, as it can avoid the omission of abnormal information. The result has certain guiding significance for further prospection works in this area. © 2016, Science Press. All right reserved.

Zhang N.,Xinjiang Institute of Ecology and Geography | Zhang N.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | Zhou K.,Xinjiang Institute of Ecology and Geography | Zhou K.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology
Scientia Geologica Sinica | Year: 2016

Alteration minerals have diagnostic features in the spectrum, but it belongs to a kind of weak information in comparison with other targets, and it needs data mining to show the implicit information. Over the years, remote sensing workers explored methods of identification of alteration minerals, the methods of ratio and principal component analysis had been successfully applied in the multi-channel remote sensing. But the ratio methods often carried out band operations based on single spectral, ignoring the combination of spectral characteristics of altered minerals. For solving this problem, this paper used Aster data of Baogutu porphyry copper deposit, Xinjiang II and V ore body, to explore the Aster spectral response characteristics of the typical alteration minerals, using two methods of absorption band depth (RBD) and logical algorithm for alteration zoning identification research. The results showed that, due to multiple logical algorithms considering multi-spectral characteristics of alteration mineral assemblages, the recognition effect was better than single RBD method based on single spectral characteristics. It reduced the false anomalies, improved the accuracy of recognition. © 2016, Science Press. All right reserved.

Zhang C.,Zijin Mining Group Co. | Zhang C.,Peking University | Li N.,Xinjiang Institute of Ecology and Geography | Li N.,Xinjiang Key Laboratory of Mineral Resources and Digital Geology | Li N.,University of Aarhus
Ore Geology Reviews | Year: 2016

In this contribution, the largest porphyry Mo deposit in NE China, Chalukou, is selected to provide insights into the tectonic evolution of NE China. The deposit was considered to be rift-related (or Climax-type) porphyry Mo deposit developed in an extensional setting, while other researchers attributed its formation to the subduction of the Paleo-Pacific Ocean. In view of different granite petrogenesis between rift-type and subduction-type porphyry Mo deposits, geochronological and zircon Lu-Hf isotope studies have been carried out on granitic rocks associated with the Chalukou deposit. Zircon grains from the ore-host monzogranite and ore-causative granite porphyry yield weighted mean 206Pb/238U ages of 166±2Ma and 152±2Ma, with molybdenite samples yielding a Re-Os isochron age of 150±2Ma, indicating a Jurassic age for both granitic intrusion and Mo mineralization. Zircon εHf(t) values of monzogranite and granite porphyry range from 0.9 to 3.0 and from -1.4 to 0.5, respectively. When integrated with published zircon Lu-Hf isotopic data, our data suggest that the barren granites (both pre- and post-ore) were mainly derived from mantle-derived juvenile rocks, whereas the syn-ore granite requires additional involvement of old continental crust. Thus, a contribution of continental crust to Mo mineralization is suggested. The petrogenesis and geochemical data reveal that the Chalukou deposit is a subduction-related porphyry Mo deposits and not rift-related. Integrated evidence links its formation to the southeastward subduction of the Mongol-Okhotsk Ocean, instead of the westward subduction of the Paleo-Pacific Ocean. © 2016 Elsevier B.V.

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