2010 Vol. 16, No. 1

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DISCOVERY OF THE EARLY PLEISTOCENE KUNLUNHE CONGLOMERATE IN GOLMUD OF QINGHAI PROVINCE AND ITS GEOLOGICAL SIGNIFICANCE
ZHAO Xi-tao, HU Dao-gong, WU Zhong-hai, LIU Qi-sheng, ZHANG Yao-ling, XUE La-mei
2010, 16(1): 1-10.
Abstract (249) HTML (239) PDF (640KB)(10)
Abstract:
The Kunlun River originating in the Kunlun Mountains is one of main tributaries of the Golmud River. The reported Neocene and Quaternary strata are mainly distributed in the Kunlun Pass area, whereas in the valley of the Kunlun-Golmud River only occur the strata younger than the Middle Pleistocene. Therefore, a conception of the "Kunlun-Huanghe movement" was proposed for the time span of 1.1 to 0.6 Ma. In this paper we report the discovery of over 20m of Ca-cemented fluvial gravels in the valley of Kunlun River, named the Kunlunhe conglomerate. Its distribution, the unconformity with such overlying strata as the Nachitaigou Formation, the Sanchahe Formation and the deposits on lower terraces, as well as the ESR dating of the Ca-cemented gravels (1042 ± 104 ka and 1269 ± 126 ka), all suggest that the Kunlun-Golmud River valley had been formed before 1.27~1.42 Ma, and cut deeply down to its present bottom. After that, The repeated incisions and accumulations after that were not due to tectonic movements, but to erosion and movement caused by climatic changes during the glacial-interglacial periods. Furthermore, the strong uplift of the Kunlun Mountains with respect to the Qiadam Basin should occur before at least 1.27~1.42 Ma.
TECTONIC ENVIRONMENT OF NAIJ TAL GROUP IN THE EAST KUNLUN OROGENIC BELT
NI Jin-yu, HU Dao-gong, ZHOU Chun-jing
2010, 16(1): 11-20.
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Abstract:
The Naij Tal Group, an important stratigraphic unit, is of great significance to reconstruction of the geological evolution of the East Kunlun orogenic belt during the Early Paleozoic, but divergent opinions have been proposed about its tectonic environment. Based on close geological survey, a geochemical analysis has been made on the clastic rocks in the OrdovicianSilurian Naij Tal Group in East Kunlun orogenic belt, and the results demonstrate that this group was formed in passive continental margin, rather than in fore-arc basin on active continental margin. The study provides geochemical evidence for the study of early Paleozoic tectonic evolution in east Kunlun orogenic belt.
SHRIMP ZIRCON U-Pb AGES OF RHYOLITE FROM THE NAIJ TAL GROUP IN THE EAST KULUN OROGENIC BELT
ZHANG Yao-ling, ZHANG Xu-jiao, HU Dao-gong, SHI Yu-ruo, LU Lu
2010, 16(1): 21-27, 50.
Abstract (291) HTML (184) PDF (737KB)(11)
Abstract:
The Naij Tal Group is a major lithostratigraphic unit with a complex composition in the East Kunlu Paleozoic orogenic belt, and there has long been debate on its formation time. The An average SHRIMP zircon 206Pb/238U age of 450.4 ± 4.3 Ma has been obtained for 15 rhyolite samples collected from the Shihuichang Formation of the Naij Tal Group south of Gelmud. It was interpreted as the age of a volcanic activity, so the Shihuichang Formation of the Naij Tal Group can be considered to form in the Late Ordovician.
ZIRCON U-Pb DATING OF THE RHYOLITE-DACITE PORPHYRY IN THE SANDAOWAN OF EAST KUNLUN MOUNTAINS AND ITS GEOLOGICAL SIGNIFICANCE
ZHOU Chun-jing, HU Dao-gong, BAROSH P J, WU Zhen-han, ZHANG Yong-qing, GENG Jian-zhen, HAO Shuang, NI Jin-yu, ZHANG Yao-ling
2010, 16(1): 28-35.
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The Sandaowan rhyolite-dacite porphyry, located to the west of the Golmud River, about 55 km from south of Golmud City, is an intrusive vein of volcanic craters. It intruded into the clastic rocks, named Habalayigou group as one of the Nachitai unit in this region. A sample No. B727-1 was collected from the Sandaowan rhyolite-dacite porphyry rock. We used the LA-MC-ICPMS method of Zircon U-Pb Dating in this article. The 25 zircons from No. B727-1 yield a mean value of (425.9 ± 2.6) Ma of 206Pb/238U, which is interpreted as the age of the volcanism. The result shows that the volcanic crater was one of the eruptive center during Late collision of the Early Paleozoic in this region. Besides, it reveals a low time restrict to the Habalayigou group, implying that the Habalayigou strata formed before the Middle Silurian. These results conflict with previous 40Ar/39Ar whole rock ages of 147.96Ma for the rhyolite-dacite porphyry from the same rock.
ZIRCON U-Pb AGE FROM SYNTECTONIC GRANITIC PORPHYRY IN THE MIDDLE KUNLUN FAULT BELT AND ITS TECTONIC SIGNIFICANCE
LU Lu, HU Dao-gong, ZHANG Yong-qing, WU Zhen-han
2010, 16(1): 36-43.
Abstract (123) HTML (101) PDF (657KB)(5)
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A measurement by LA-MC-ICP MS for two samples of zircon from granitic porphyry collected at Golmud, in south part of the middle Kunlun fault belt has yielded two U-Pb ages of 408.5 ± 2.3Ma and 391.2 ± 3.4Ma, respectively. The results show that the middle Kunlun fault belt should be a newly generated fault belt superposed on the middle Kunlun suture zone, and formed during the tectonic deformation of continental interior in late Caledonian orogeny of the east Kunlun Mountains.
ZIRCON U-Pb AGES FOR RHYOLITIC TUFFS OF THE NAOCANGJIANGOU FORMATION IN THE EAST KULUN OROGENIC BELT AND THEIR IMPLICATION
WU Fang, ZHANG Xu-jiao, ZHANG Yong-qing, ZHANG Yao-ling
2010, 16(1): 44-50.
Abstract (197) HTML (113) PDF (516KB)(9)
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By using La-Mc-ICPMC method, accurate zircon U-Pb dating has been made for volcanic rock samples from the Naocangjiangou Formation in the Xiugou basin of the East Kunlun orogenic belt. The zircons from the rhyolitic tuff (sample DG25-4) showed oscillatory girdles in its cathodeluminescence image, indicating a typically magmatic origin. The 206Pb/238U surface ages of 15 magmatic zircons are concentrated in the range of 239-249 Ma, averaging 243.5 ± 1.7 Ma, which records the forming age of those volcanic rocks, that is, the Naocangjiangou Formation was formed in the early Middle Triassic. Early Paleozoic and Proterozoic zircons were also found in volcanic rocks of the formation, suggesting the possible presence of Proterozoic basement in the Kunlun southern terrain.
EVIDENCE OF ZIRCON U-Pb AGES FOR THE FORMATION TIME OF THE EAST KUNLUN LEFT-LATERAL DUCTILE SHEAR BELT
ZHANG Zi-cheng, ZHANG Xu-jiao, GAO Wan-li, HU Dao-gong, LU Lu
2010, 16(1): 51-58.
Abstract (174) HTML (95) PDF (680KB)(4)
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The large-scale East Kunlun left-lateral ductile shear belt was formed by an oblique collision between the Bayan Har-Songpan-Ganzi terrain and the southern East Kunlun terrain during the Late Triassic. During the Cenozoic, this ductile shear belt was transformed into a brittle leftlateral strike-slip belt, and became the north boundary for the eastward "escape" of the QinghaiTibet Plateau. The La-MC-ICPMS dating for two syntectonic granite-porphyry veins in the large ductile shear belt yielded two weighted zircon 206Pb/238U ages of 196.4 ± 2.3 Ma and 195.1 ± 1.6 Ma. These ages suggest that the East Kunlun left-lateral ductile shear belt should form during the early Yanshanian Movement.
EXTRACTION OF LITHOLOGIC INFORMATION FROM THE EAST KULUN OROGENIC BELT USING ASTER REMOTE SENSING IMAGE
GAO Wan-li, ZHANG Xu-jiao, WANG Zhi-gang, ZHANG Zhi-cheng, ZHANG Yao-ling
2010, 16(1): 59-69.
Abstract (144) HTML (78) PDF (1142KB)(6)
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By using ASTER data and such methods for extraction of lithologic information as major composition image and the mineral index, a discrimination for and extraction of lithologic information has been made in the Wenquan Reservoir area of the East Kunlun orogenic belt. The results show that the major composition image and the mineral index can well reveal the composition of rocks. Clearly shown on ASTER images are lithostratigraphic units covering a relatively large area, including Proterozoic crystalline limestone, the limestone in Permian Malzheng Formation, the sandstone in Middle Triassic Naocangjiangou Formation and the clastic rocks in Upper Triassic Babaoshan Formation. ASTER images would prove to be an effective method for extraction of lithologic information in bedrock exposed areas, especially for carbonate rocks as well as sedimentary and volcanic rocks with varying SiO2 contents. But for the rock units of small thickness or altered rocks, the methods need to be improved.
APPLICATION OF REMOTE SENSING TECHNIQUE IN THE MAPPING OF CENOZOIC GEOLOGY OF THE EAST KUNLUN MOUNTAINS
XUE La-mei, ZHAO Xi-tao, ZHANG Yao-ling, GAO Wan-li
2010, 16(1): 70-77.
Abstract (147) HTML (74) PDF (622KB)(5)
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According to the color variations of different geological bodies in the same wave band or the same geological body in different wave bands, a close geological interpretation has been made for the ETM images from the East Wenquan Basin of the east Kunlun Mountains, resulting in the establishment of interpretation makers for the Cenozoic strata and new structures. The interpretation allows us to accurately define the Cenozoic strata boundaries and Cenozoic fault locations on the ETM images. The Cenozoic strata in the mapping area can be divided into 10 mapping units based on the field survey. The Cenozoic faults include nearly NW left-lateral strike-slip faults and nearly NWW thrust nappe structures. It is believed that multispectral remote sensing image can play an important role in Cenozoic geological mapping.
WULING OROGENY IN EASTERN GUIZHOU AND ITS ADJACENT REGIONS AND ITS GEOLOGICAL SIGNIFICANCE
DAI Chuan-gu, CHEN Jian-shu, LU Ding-biao, MA Hui-zhen, WANG Xue-hua
2010, 16(1): 78-84.
Abstract (152) HTML (53) PDF (632KB)(12)
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The Wuling orogeny made a significant influence in eastern Guizhou and its adjacent regions, as reflected by the appearance of disconformities between middle and upper Proterozoic. It took its most profound expression in northern section of the Fanjing Mountain of Guizhou Province, Dayong, Yueyang and Pingjiang areas of Hunan Province, and left some regular changes on the plane toward southeast: the overlying beds from absence to presence, the contact from high-angle to low-angle and then to parallel disconformities, and metamorphism of middle Proterozoic gradually getting weaker. From the tectonic point of view, the Wuling orogeny, with its central place as stated above, brought about the withdraw and final disappearance of the Southern China ocean basin, the formation of the South China Plate by collision and convergence between Yangtze Oldland and Cathaysia Oldland, and the ocean-continent conversion in the study region during the middle Proterozoic.
SEDIMENTARY CHARACTERISTICS OF THE JIUFOTANG FORMATION DEVELOPED IN LUANPING MESOZOIC FAULT BASIN OF NORTHERN HEBEI PROVINCE
PAN Li-cheng, LI Lin-qing, LI Xiang, WU Geng-lin, ZHAO Hai-xuan
2010, 16(1): 85-95.
Abstract (176) HTML (88) PDF (811KB)(6)
Abstract:
In the Luanping area of northern Hebei Province, there appears a Mesozoic continental fault basin. Its uppermost part is occupied by the Early Cretaceous Jiufotang Formation, which consists of tremendously thick grayish green-grayish yellow clastic rocks formed under inland warmhumid climate. In general, this formation is divisible into two members. Member one begins at the base with alluvial fan deposits, as products of initial stage of the fault, and is poorly preserved because of erosion. The rest of the member is composed of fan-delta deposits, intercalated with lake deposits. Member two occurs as alluvial deposits. Under the control of Gangzi-Hongqizhen synsedimentary fault in the northwest, an outflowing-type fault lake was formed during the Jiufotang age. Two stages can be recognized in the development of the faults. The first one, spanning a short time interval, finds its expression in the transition from alluvial system to fan-delta system, leading to forms of small-area lakes and small-thickness deposits. The second stage, however, lasting as long as to the disappearance of the basin, is reflected by the transition from fan-delta system to alluvial system, bringing about the appearance of open lakes and grent thickness of deposits.
GEOCHEMISTRY AND GENESIS OF BASIC-INTERMEDIATE VOLCANIC ROCKS FROM KALADAWAN, EAST ALTUN TAGH MOUNTAINS
CUI Ling-ling, CHEN Bai-lin, YANG Nong, CHEN Zheng-le, DING Wen-jun
2010, 16(1): 96-107.
Abstract (135) HTML (60) PDF (399KB)(4)
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The Kaladawan area at eastern part of the Altyn Tagh Mountain is tectonically situated between the NE-trending Altyn Tagh strike-slip fault and the W-E-trending Northern Altyn Tagh margin fault. In the area, there appears a set of volcanic-sedimentary rocks. A geochemical study has been made on the basic-intermediate volcanic rocks. The results show two REE patterns: slight LREE-enrichment pattern and a partly flat pattern, indicating an island-arc origin. The Zr/Nb, Nb/Ta and Zr/Hf values indicates that the volcanic rocks have withstood a contamination with the crustal materials. The La-La/Sm diagram of the volcanic rocks displays a coexistence of partial melting and fractional crystallization. In the Hf-Tu-Ta and FeO-Na2O + K2O-Mg diagrams, it can be seen that the volcanic rocks of the study area belong to tholeiite-series volcanic-arc basalts. It is suggested that the volcanic rocks were formed in an island-arc environment in the upper wall of subduction zone in the early Paleozoic, with the basalts mainly derived from the mantle.
3D NUMERICAL SIMULATION OF SLOPE STABILITY OF LANCANGJIANG BRIDGE ON DALI-RUILI RAILWAY
DU Yu-ben, ZHENG Guang, JIANG Liang-wen, XU Qiang
2010, 16(1): 108-114.
Abstract (158) HTML (73) PDF (884KB)(2)
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The Lancangjiang Bridge is one of the controlled engineerings on the under-construction Dali-Ruili Railway. Along the bank slopes at which the bridge site is located there are greatly developed long-extending dip-slope joints and nearly vertical joints, The excavation area of the bridge site on right bank is below a group of large dip-slope structural planes, so the slope stability is directly related to the suitability of bridge site. Comprehensive studies show that excavation on right bank will be like to induce slip and tension crack failure affected by the dip-slope structural planes and to cause great displacement along extraversion structural planes, and even instability on whole slope, with which the specialized engineering management should be taken to deal. On the contrary, rock masses on left bank are of a relatively stable structure, and the displacement induced by engineering will mainly take place on shallow surface of excavation site, with slight deformation and limited influence area.