Time filter

Source Type

Liu C.-J.,Chang'an University | Pei X.-Z.,Chang'an University | Pei X.-Z.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | Li Z.-C.,Chang'an University | And 8 more authors.
Geological Bulletin of China | Year: 2012

The Neoproterozoic granitic gneisses in Tianshui area are located in the Xinyang-Yuanlong ductile shear belt which is the boundary between the North Qinling orogenic belt and the North Qilian tectonic zone. Geochemistry, petrogenesis and tectonic setting of the granitic gneisses are discussed in this paper. The granitic gneisses are rich in SiO2 and Al2O3, with A/CNK being 1.104~1.389, showing the supersaturation of Al and Si and suggesting the features of typical strongly peraluminous S-type granite. The ΣREE range from 128.27×10-6 to 242.09×10-6. Chondrite-normalized REE patterns show a rightward inclination with medium negative Eu anomalies. The trace element geochemistry is characterized by positive anomalies of Cs, Rb, Ba, Th, U, K, La, strongly-depleted negative anomalies of Nb, Ta, Ti, Hf, and evident negative anomalies of Ba, P, Sr. The granitic gneisses have features of crust-derived and typical continent-continent syn-collisional granites. The Paleoproterozoic Qinling Group whose protoliths were immature psammites containing higher pelitic compositions probably served as the source rocks. The generation of granitic gneisses resulted from dehydration melting due to the breakdown of micaceous minerals, with the possible existence of some fractional crystallization. The granitic gneisses suggest a collision between the North Qinling micro-block and its adjacent block in the Early Neoproterozoic period. It is a response of the assembly of Rodinia in West Qinling.


Xu T.,Chang'an University | Pei X.-Z.,Chang'an University | Pei X.-Z.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | Li R.-B.,Chang'an University | And 9 more authors.
Geology in China | Year: 2013

Zhangyangou bimodal volcanic rocks are located in Hengxianhe area, Sanchazi Lueyang segment of Mian -Lue tectonic zone. The bimodal volcanic rocks consist of metamorphosed basic volcanic rocks and metamorphosed acid-intermediate rocks in close association, and the protoliths are sub-alkaline basalt and sub alkaline rhyolitic dacite. On account of the higher REE concentrations in basalt than in rhyolitic-dacite, the authors hold that the origin of rhyoliticdacite was partial melting of the crustal material rather than the fractional crystallization of the basaltic magma. Basic volcanic rocks show the intraplate geochemical characteristics such as high Zr concentrations and Zr/Y ratios, and their marks of arc result from the hybridism of the crustal material. The result of U-Pb isotope dating by means of Laser Ablation Inductively Coupled Plasma Mass Spectrometry makes it clear that the formation age of the rhyolite is (728±10) Ma n=4 MSWD=0.14). Combined with the regional geological background, the authors consider that Zhangyangou bimodal volcanic rocks were formed in a continental rift environment under the crust extensional mechanism. The formation of Zhangyangou bimodal volcanic rocks heralded the opening of Neoproterozoic Ocean. This new achievement is of important significance both for the further study of the evolution of Mian Lue tectonic zone and the breakup of Rodinia sunercontinent and other continents on the north margin of the Yangtze block.


Wang Y.-C.,Chang'an University | Wang Y.-C.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | Pei X.-Z.,Chang'an University | Pei X.-Z.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | And 15 more authors.
Geological Bulletin of China | Year: 2012

The newly identified Mesoproterozoic granitic gneisses are located in Paleoproterozic Longshan Group at the eastern end of Qilian Orogenic belt. In order to accurately determine the formation age of granitic gneisses from Changningyi, the authors carried out single grain zircon micro area U-Pb isotope dating by means of Laser Ablation Inductively Coupled Plasma Mass Spectrometry. The Th/U ratios of zircons from granitic gneisses are between 0.50 and 2.09, and CL images show that the internal zircon has developed typical oscillatory girdle structure of magma growth, which belongs to the product of magma crystallization. And the original rock crystallization age of granitic gneiss is 1765Ma±57Ma, suggesting that granite rock was produced in early Mesoproterozoic period, and was probably formed in an post-orogenic environment, under which North China Block was experiencing the Lüliang movement. In addition, from the captured inherited magma zircon, the authors obtained the inherited ages of 1.95Ga and 2.20Ga. In combination with regional geological data and on the basis of a comprehensive study and analysis, the authors found that Qilian block remained a southwestern part of North China Block in Mesoproterozoic, for they had the same crystalline basement and structural properties. Besides, they both experienced the post orogenic stage and intracontinental stretch cracking stage after Lüliang movement. So they were probably closely related to the polymerization and cracking of Columbia supercontinent.


Sui L.,Chang'an University | Sui L.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | Yang Y.,Chang'an University | Yang Y.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education
Cehui Xuebao/Acta Geodaetica et Cartographica Sinica | Year: 2012

Based on the existing post-processing methods of LiDAR data, a "separated step-by-step" filtering method of point cloud is proposed. First, a "rough" filtering method is applied to the LiDAR point cloud and the "ground points hypothesis" and "non-ground points hypothesis" are gained. Then, a causal auto-regressive model (car model) is imported to do modeling of the ground surface and hypothesis test for the two classes of point clouds, and ground points and non-ground points are classified by the results of the hypothesis testing. Finaly, the reliable classification results are gained. Compared to the "least squares prediction method" and "mathematical morphology", the results of LiDAR point cloud filtering by the "separated step-by-step" processing method are more reliable.


Dang B.,Chang'an University | Dang B.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | Zhao H.,Chang'an University | Zhao H.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | And 5 more authors.
Zhongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Central South University (Science and Technology) | Year: 2013

Triassic Yanchang Formation Chang 10 oil layer is a new oil-bearing layer which was found in the middle-east of Odors basin in 2007. Taking it as an example, on the basis of field outcrop and core observation combined with the indoor sensitivity test, sensitivity test, casting slice physical data, X-ray diffraction, SEM, mercury injection data and so on, the characteristics of reservoir sensitivity and its microscope mechanism were studied. The results show that the studied area Chang10 Reservoir possesses the characteristics such as slight water sensitivity and velocity sensitivity strata, medium-low to low saline sensibility, low-medium to low alkali sensitivity and high-medium to high acid sensitivity. The sensitivity is related to the existence of sensitive minerals such as chlorite-film, laumontite and the complex pore texture formed by diagenesis.


Liu T.-J.,Chang'an University | Pei X.-Z.,Chang'an University | Pei X.-Z.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | Liu C.-J.,Chang'an University | And 9 more authors.
Geological Bulletin of China | Year: 2014

Detailed observations of CL images and LA-ICP-MS detrital zircon U-Pb ages of the metasandstone samples from Liangdang area of Western Qinling provide information about the provenance of Taiyangsi Formation. The ages of detrital zircons show that the sedimentary ages of the Taiyangsi Group range from 426 to 420Ma, suggesting Ludlow to Pridoli period. The U-Pb detrital zircon ages can be assigned to four age groups: 500~420Ma, 955~550Ma, 1866~1227Ma and 3039~2132Ma. Early Paleozoic age group shows the most strong peak age of 438Ma, implying that the material source was mainly from the north margin of Western Qinling tectonic belt. The detrital zircons with Neoproterozoic age were related to the magma of the north margin of Western Qinling tectonic belt and Northern Qilian orogenic belt in the Neoproterozoic. The detrital zircons with Mesoproterozoic age and Paleoproterozoic-Neoarchaean age were mainly from the basement of Northern Qilian orogenic belt and the north margin of Western Qinling tectonic belt. A comprehensive analysis reveals that the material source of Taiyangsi Formation was mainly from the north margin of Western Qinling tectonic belt.


Deng W.,Chang'an University | Pei X.,Chang'an University | Pei X.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | Liu C.,Chang'an University | And 9 more authors.
Geological Bulletin of China | Year: 2016

A suite of syenogranites is exposed in the Chahantaolegai area along the eastern section of East Kunlun Orogenic Belt. LA-ICP-MS zircon U-Pb weighted average ages is 239.9±0.7 Ma, suggesting the formation of syenogranites in Middle Triassic. According to the geochemical characteristics, it is suggested that Chahantaolegai syenogranites belong to peraluminous high-potassic calc-alkaline series. They are characterized by high SiO2, Al2O3, K2O and low TiO2 and Na2O values. A/CNK=1.05~1.13 (average A/CNK=1.10), K2O/Na2O ratios are about 0.95~1.16, and Rittmann index σ=1.56~2.24; the content of corundum exceeds 1%, as shown by CIPW standard mineral calculation. The existence of rock-forming minerals such as muscovite suggests that the syenogranites are of S-type. The values of rare earth elements are 61.47×10-6~145.23×10-6. The chondrite-normalized REE patterns of the samples show enrichment of LREE ((La/Yb)N=15.83~27.11)and strong negative Eu anomalies (δEu=0.26~0.49). The primitivemantle-normalized trace element diagrams show enrichment of Rb, La and Th and depletion of Ba, Ta, Sr, P and Ti. Characteristics of trace and earth elements suggest that syenogranites were from the earth's crust. It is suggested that the syenogranites resulted from melting of the sedimentary rocks of the upper crust. Combined with regional studies, the authors hold that Chahantaolegai syenogranites are of the transitional type formed in the transformation from subduction to syn-collision, being a product of the late stage of the subduction of Buqinshan-A'nyemaqen Ocean on the southern margin of the East Kunlun in Middle Triassic. © 2016, Science Press. All right reserved.


Yang S.,Chang'an University | Pei X.,Chang'an University | Pei X.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | Li R.,Chang'an University | And 9 more authors.
Geological Bulletin of China | Year: 2016

Detailed statistics of gravel composition, gravel granulometry and the LA-ICP-MS U-Pb dating of detrital zircons from conglomerate bed in Delisitan of Buqingshan show that this conglomerate was derived from the nearby place with rapid accumulation. This conglomerate consists mainly of quartzite and granite and subordinately of siliceous rocks and basic rocks, with minor sand-stone and limestone. The coefficients of dispersion are 1.54~2.02 for the gravel of conglomerate. The detrital zircon age spectra can be divided into three groups: (1) Early Ordovician-Late Silurian age group, 499~409 Ma, with the peak value being 426 Ma, corre-sponding to the tectono-magmatic events associated with Proto-Tethys northward subduction and collision at the end of Early Paleozoic; (2) Neoproterozoic age group, 744~619 Ma, with the peak value being 744 Ma, corresponding to the breakup of Rodinia supercontinent; (3) Paleoproterozoic age group, 2443 Ma, corresponding to the tectono-magmatic hydrothermal event of East Kunlunin Paleoproterozoic. An integrated analysis of the U-Pb detrital zircon ages and sedimentology characteristics show that the granite gravel was derived from magmatic arc in Caledonian in northern East Kunlun Orogen, the gravel of quartzite and metamorphic rocks was from the East Kunlun metamorphic rock series in basement, and the gravel of sedimentary rocks might have come from the early sedimentary formation in the orogenic belt. A comprehensive analysis reveals that the Gequ Formation is a mollasse formation of the littoral-shallow facie which deposited on anactive continental margin. It represents both the beginning of the Paleo-Tethys northward subduction and the sedimentary responding of tectonics at the beginning of the subduction. © 2016, Science Press. All right reserved.


Wang Y.-Y.,Chang'an University | Pei X.-Z.,Chang'an University | Pei X.-Z.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | Liu C.-J.,Chang'an University | And 9 more authors.
Geological Bulletin of China | Year: 2014

Choosing the Shujiaba Group detrital rocks in Shujiaba area as the study object and using LA-ICP-MS zircon U-Pb isotope chronology, the authors studied the sedimentary age and material source of the Shujiaba Group. 413Ma, the mean of the minimum ages group, indicates that the sedimentary age of Shujiaba Group should be the Middle Devonian. Four groups can be recognized from the zircon ages spectrum: Sinian-Early Paleozoic age group (619~409Ma), with the peak value of 445Ma;Neoproterozoic age group (930~735Ma), with the peak value of 849Ma; Mesoproterozoic age group (1760~1033Ma); and Paleoproterozoic-Neoarchaen age group (3095~2478Ma). The age group information indicates that the material sources were mainly derived from North Qilian orogenic belt, the northern margin of West Qinling tectonic zone and the basement of North China block, of which the North Qilian orogenic belt and the northern margin of West Qinling tectonic zone made the major contribution, with the last one playing the leading role. The material source features and regional geology suggest that the Shujiaba Group was formed in a rifted basin resulting from the transitional tectonic setting from syn-collision (compressional setting) to post-collision (extensional setting).


Dang B.,Chang'an University | Dang B.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | Zhao H.,Chang'an University | Zhao H.,Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education | And 7 more authors.
Diqiu Kexue - Zhongguo Dizhi Daxue Xuebao/Earth Science - Journal of China University of Geosciences | Year: 2013

Carboniferous volcanic rocks are widely distributed in northern Alashan League and its neighboring areas, and their genesis and tectonic setting have always been an issue of controversy. Based on analysis of petrology and petrogeochemistry characteristics of Carboniferous volcanic rocks in the study area, this paper attempts to clarify the palaeo-tectonic setting and provides independent evidence for understanding the properties of Carboniferous basin. The volcanic rocks are dominated by intermediate-acidic volcanic rock. The majority of basalts, basaltic-andesite and andesite fall into sub-alkaline series. Mg# number of this suit ranges from 0.29 to 0.69. These volcanic rocks samples exhibit strong depletion in the high field strength elements Nb, Ta and Ti, and minor enrichment in the LREE. In terms of REE, (La/Yb)N number ranges from 2.19 to 10.10, showing less obvious Eu depletion (δEu=0.81 to 1.08), and slightly right-inclined REE distribution patterns, with higher εNd(t) value (+1.10 to +6.35). The samples show not only the marks of those within plate setting as a whole, but also those of subduction zone. Combining with the regional geological characteristic, we conclude that the Carboniferous magmatic activity in the study area generated in a within-plate setting, with variable degrees of contamination of crust during magma ascending, and probably related to mantle plume event.

Loading Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education collaborators
Loading Key Laboratory of Western Mineral Resources and Geological Engineering of Ministry of Education collaborators