Bangong Co Research Articles

Hydrochemical Characteristics and Quality Evaluation of Irrigation and Drinking Water in Bangong Co Lake Watershed in Northwest Tibetan Plateau

Bangong Lake is a narrow and long lake in the arid region of the plateau in northern Tibet. The salinity of the east of the lake is different from that the west, resulting in differences in the natural environment and human living conditions on each side. Watershed hydrochemical analysis and spatial statistical analysis can help to understand regional hydrochemical evolution and water quality evaluation. In this study, the hydrochemical characteristics of surface water (glacier, river, and lake) and groundwater in the Bangong Co Lake Watershed were investigated to reveal the relationships between various water bodies. The drinking water quality index (DWQI) and USSL classification were applied to assess groundwater quality suitability for agricultural and drinking purposes. The hydrochemical characteristics show the differences among water bodies and their spatial distribution. The analyzed groundwater and surface water samples, such as river water and glaciers, were mainly Ca-HCO3-type and the lake water was mainly categorized as Na-Cl-type with some Na-HCO3-Cl type. The lake water’s chemical components are mainly affected by evaporative karst decomposition. The main mineralization process of groundwater and river water was related to the dissolution of reservoir minerals, such as dolomite and calcite, as well as halite. The drinking water quality index (DWQI) indicates that 79% of the groundwater samples in the study area were of good enough quality for drinking. In terms of irrigation water quality, the electrical conductivity (EC), calculated sodium adsorption ratio (SAR), and magnesium hazardous ratio (MHR) showed that more than 13% of the total samples were not suitable for irrigation. However, the USSL classification indicated that glacier and river water are relatively suitable for irrigation. Additionally, some groundwater and lake water has very high alkalinity or salinity, which is alarming when considering them for irrigation.

Hydrothermal Zircon Geochronology in the Shangxu Gold Deposit and its Implication for the Early Cretaceous Orogenic Gold Mineralization in the Middle Bangonghu–Nujiang Suture Zone

AbstractAs a typical orogenic gold deposit in Tibet, Shangxu gold deposit is located at the Bangong Lake–Nujiang River Metallogenic Belt in the south of Qinghai–Tibet Plateau. In this paper, zircon U‐Pb dating, trace elements and Hf isotopic analysis were performed on Au‐bearing quartz veins in the Shangxu gold deposit. Zircons from Au‐bearing quartz veins can be divided into three types: detrital, magmatic, and hydrothermal zircons. There are two age peaks in detrital zircons: ca. 1700 Ma and ca. 2400 Ma. There are two groups of concordant ages including 157 ± 4 Ma (MSWD = 0.69) and 120 ± 1 Ma (MSWD = 0.19) in magmatic zircons, in which εHf(t) value of ca. 120 Ma from the magmatic zircons range from +8.24 to +12.9. An age of 119 ± 2 Ma (MSWD = 0.42) was yielded from hydrothermal zircons, and their εHf(t) values vary between +15.7 and +16.4. According to sericite Ar‐Ar age, this paper suggests that an age of 119 ± 2 Ma from hydrothermal zircons represent the formation age of the Shangxu gold Deposit, and its mineralization should be related to the collision between Lhasa Block and Qiangtang Block. The metallogenic age is basically the same as the diagenetic age of Mugagangri granite, and εHf(t) value of hydrothermal zircon is significantly higher than that of the contemporaneous magmatic zircon, which indicates that there is a genetic relationship between the gold mineralization and the deep crust‐mantle magmatism.

U-Pb Detrital Zircon Ages and Geochemical Features of the Jingxing Formation, (Qamdo Basin, Tibet: Implications): Inferences for the Metallogenic Model of the East Tethys Evaporite

Qamdo basin is located between the suture zone of Jinsha River (Ailao Mountains) and that of Ban Gong Lake (Nujiang) in the eastern Tethys. Part of the Jingxing Formation is deposited in the southwest of the basin. In this study, two profiles were investigated from the north and south of Qamdo basin. The characteristics of detrital zircon LA-ICP-MS U-Pb age, and the main and trace elements of sandstone were analyzed. The characteristics of major and trace elements showed that the tectonic setting of the study area is mainly composed of a relatively stable active continental margin and a passive continental margin, showing characteristics of a continental island arc. The weathering degree of Jingxing Formation in the Qamdo area is lower than that in the Lanping-Simao area, which may be closer to the origin. The age distribution characteristics of detrital zircon grains indicate that the Qiangtang Block, Youjiang basin, and Yangtze area jointly constitute the provenance of the Qamdo-Lanping-Simao basin. Both basins may be part of a large marine basin with unified water conservancy connection before evaporite deposition. Metamorphic seawater from the Qamdo basin may migrate to the Lanping-Simao basin and even the Khorat basin, where evaporite was deposited.

Water chemistry and source analysis of major ions of Bangong Lake in Tibetan Plateau

Bangong Lake,was an inland lake on the Tibetan Plateau, which was an international lake across China and India. The water chemistry characteristics were analyzed by testing the chemical composition of the lake water in Bangong Lake. The Gibbs diagram was used to explore the main controlling factors of lake water, and the main ion source of lake water was described in combination with the proportion of dissolved ions. The results showed that the center was brackish water and the east was fresh water of the Bangong Lake with a weak alkaline water. From the surface to the bottom, the temperature, dissolved oxygen and redox potential were decreasing, while the conductivity was increasing. The main cation of lake water was Na+, the main anion was Cl-, and the main chemical type was SO4-Cl-Na. The soluble ions in the central water were mainly controlled by evaporation and concentration, while the soluble ions in the eastern water were mainly controlled by rock weathering. The cations in the water were mainly derived from the silicate rock weathering and the dissolution of evaporite, and the anions was mainly derived from the dissolution of evaporite.

Sedimentary successions and onset of the Mesozoic Qiangtang rift basin (northern Tibet), Southwest China: Insights on the Paleo- and Meso-Tethys evolution

Abstract The Mesozoic Qiangtang Basin is investigated to reconstruct the tectonic evolution of the Paleo- and Meso-Tethys Oceans. We present a detailed sedimentary facies analysis of the Nadi Kangri and Quemoco formations and the systematic zircon U Pb ages of the volcanoclastic rocks in the Nadi Kangri Formation to understand the onset and nature of the Mesozoic Qiangtang Basin. The Nadi Kangri Formation, consisting of volcanic-volcanoclastic facies associated with alluvial-diluvial facies association, which represents continental volcanic succession. The Quemoco Formation, consisting of braided fluvial, restricted platform and tidal flat facies associations, represents continental siliciclastic and marine carbonate successions. The deepening-upward transgressive sequences reconstructed from the two formations are indicative of a rift basin. Zircon U Pb ages of the volcanoclastic rocks in the bottom, middle, and upper sections of the Nadi Kangri Formation in the Fanghu area are 221.7 ± 1.3 Ma, 217.0 ± 1.5 Ma, and 207.1 ± 1.3 Ma, respectively. Combined with the previous zircon ages of the Nadi Kangri Formation, we interpreted that 221.7–220.4 Ma is the initial age for the onset of the Mesozoic rift basin. An evolution pattern for the Tethys Ocean and Mesozoic Qiangtang Basin has been proposed based on the magmatism, metamorphism, sedimentary sequence, and deformation data obtained from the Kunlun (KLT), Hoh Xil–Bayan Har (HBT), North Qiangtang (NQS), Central Uplift Belt (CUB), South Qiangtang (SQS), and North Lhasa subterranes/terranes (NLS) during the Early Triassic–Middle Jurassic. Based on the new data, we interpret a double-sided subduction and subsequently a collision of the Paleo-Tethys Ocean beneath the KLT to north and NQS to south, probably occurring at ca. 252-237 Ma and 237-227 Ma, respectively. This interpretation is consistent with the Late Triassic residual sea (ocean) model that attributed to the origin of the Hoh Xil–Bayan Har Basin. The QT and NLS experienced a strong extension between ca. 225 and 201 Ma owing to the rapid expansion of the Bangong Lake–Nujiang Ocean (Meso-Tethys Ocean), which is consistent with the massive volcanic eruption and deposition of volcanic sediments in the QT and NLS. In addition, the QT and NLS experienced a stabilized subsidence during 201–166 Ma, due to the existence of the mature Bangong Lake–Nujiang Ocean.

Late Quaternary slip-rate along the central Bangong-Chaxikang segment of the Karakorum fault, western Tibet

Insight into the spatial and temporal changes of slip-rate is essential to understand the kinematic role of large strike-slip faults in continental collision zones. Geodetic and geologic rates from present to several million years ago along the Karakorum fault range from 0 to 11 mm/yr. Here, we determine the first late Quaternary slip-rate at the southern end of the linear Bangong-Chaxikang segment of the Karakorum fault, using cumulative offsets (20–200 m) of fans and terraces at three sites, as well as 74 new 10 Be surface-exposure ages to constrain the age of these offset geomorphic markers. The rate is >3 mm/yr at sites Gun and Chaxikang, and it is >1.7–2.2 mm/yr at the Gar fan site. Together with rates obtained along the southernmost Menshi-Kailas segment, the Karakorum fault slip-rate seems to increase southeastward from south of Bangong Lake to Kailas (from >3 to >8 mm/yr). These Karakorum fault slip-rate data (>3–8 mm/yr), together with the total length of the fault (>1000 km) and its initiation age (>13–23 Ma), confirm that the Karakorum fault is the major fault accommodating dextral strike-slip motion NE of the western Himalayas. The dextral Karakorum fault in the south and the conjugate left-lateral Longmu Co–Altyn Tagh fault system in the north are thus the major strike-slip faults of western Tibet, which contribute to eastward extrusion of Tibet.

Zircon U‐Pb Geochronology and Hf Isotopic Constraints on Petrogenesis of Plagiogranite from the Cuomuqu Ophiolite, Bangong Lake Area, North Tibet

AbstractField observation, geochemical signatures and zircon Hf isotope data indicate that Cuomuqu ophiolite in the Bangonghu area was formed in a back‐arc basin (BAB) above a supra‐subduction zone (SSZ). Zircon U‐Pb dating of the diabase from the Cuomuqu massif yielded an age of 164.3±1.9 Ma, thus indicating that the ophiolite complex was formed in the Middle Jurassic during back‐arc extension of the mature Bangonghu‐Nujiang Ocean. The zircon εHf(t) and TDMC values of the plagiogranite are similar to the εHf(t) and TDM of the diabase, respectively. The mode of occurrence of plagiogranites and their bulk‐rock and Hf isotope characteristics indicate that they were derived from the mantle, associated with the surrounding gabbro and diabase, and were formed by partial melting of altered and hydrated mafic rocks under shear conditions during lateral drifting of the oceanic crust. The zircon U‐Pb age of the plagiogranite is 156.4±1.4 Ma, and it is 7.9 Ma younger than the hosting diabase. In this study, zircon chronological and Hf isotopic data were tentatively analyzed to determine the genesis of plagiogranites in the Cuomuqu ophiolite complex.

Re-Os isotopic constraints on the evolution of the Bangong-Nujiang Tethyan oceanic mantle, Central Tibet

Geochemical (including Re-Os isotopic) studies of the mantle rocks of ophiolites in the Bangong-Nujiang suture zone in central Tibet have provided a coherent picture of the evolution of the Bangong-Nujiang Tethyan oceanic mantle from mid-ocean ridge (MOR) to subduction-zone (SSZ) settings.Clinopyroxene (cpx)-harzburgites and lherzolites in the Bangong Lake ophiolite were formed in a MOR setting, as demonstrated by the Cr# of spinels (<0.60) and whole-rock LREE-depleted patterns. Suprachondritic 187Re/188Os ratios (up to 1.833) of cpx-harzburgites and their spinels can be explained by interaction with melts derived from high Re/Os sources. Re-depletion (TRD) model ages (0.48-0.55Ga) suggest these rocks may represent a Pan-African domain beneath the Gondwana continent. High TiO2 contents of spinels and whole-rock samples imply that the lherzolites were formed through a refertilization process. Similarly, Re-Os isotopic systematics of sulfides in the lherzolites (187Re/188Os: 0.173-1.717, 187Os/188Os: 0.12646-0.17340) demonstrate that they are mixtures of primary and secondary sulfides. 187Os/188Os ratios (0.1211-0.1226) of whole-rock lherzolites give TRD ages of 0.73-0.97Ga, indicating the presence of Neoproterozoic lithospheric mantle under the spreading ridges.Mantle rocks in the SSZ-type ophiolites from Bangong Lake, Dongqiao and Nagqu reflect the complex evolution of the Bangong-Nujiang oceanic mantle during the SSZ stage. Most harzburgites from the Bangong Lake ophiolite give TRD ages of 1.0-1.5Ga, possibly representing relics of a Mesoproterozoic lithospheric mantle. However, three samples have both high Os contents (1.32-4.45ppb) and near-chondritic 187Os/188Os (0.1260-0.1297), and may represent Mesozoic oceanic lithospheric mantle. 187Os/188Os ratios of dunites and harzburgites from the Dongqiao and Nagqu ophiolites vary from 0.1174 to 0.1316 and give TRD ages up to 1.43Ga, also suggesting the existence of a Mesoproterozoic lithospheric mantle which has experienced mantle refertilization and later metasomatism caused by percolation of several generations of melts and/or fluids.We interpret the old mantle domains in the Bangong-Nujiang ophiolite belt as relics of ancient sub-continental lithospheric mantle (SCLM), which may have survived during the opening of the Bangong-Nujiang Tethyan ocean basin, and subsequently were incorporated into Mesozoic oceanic lithospheric mantle.

The Bangong Lake ophiolite (NW Tibet) and its bearing on the tectonic evolution of the Bangong–Nujiang suture zone

The Jurassic Bangong Lake ophiolite, NW Tibet, is a key element within the western part of the Bangong–Nujiang suture zone, which marks the boundary between the Lhasa and Qiangtang blocks. It is a tectonic mélange consisting of numerous blocks of peridotite, mafic lavas and dikes. The mantle peridotites include both clinopyroxene-bearing and clinopyroxene-free harzburgites. The Cpx-bearing harzburgite contains Al-rich spinel with low Cr#s (20–25), resembling peridotites formed in mid-ocean ridge settings. On the other hand, the Cpx-free harzburgite is highly depleted with Cr-rich spinel (Cr# = 69–73), typical of peridotites formed in subduction zone environments. Mafic rocks include lavas of N-MORB and E-MORB affinity and boninites. The N-MORB rocks consist of pillow lavas and mafic dikes, whereas the E-MORB rocks are brecciated basalts. The boninites have high SiO 2 (53.2–57.9 wt%), MgO (6.5–12.5 wt%), Cr (166–752 ppm) and Ni (63–213 ppm) and low TiO 2 (0.22–0.37 wt%) and Y (5.34–8.10 ppm), and are characterized by having U-shaped, chondrite-normalized REE patterns. The N-MORB and E-MORB lavas probably formed by different degrees of partial melting of primitive mantle, whereas the boninites reflect partial melting of depleted peridotite in a suprasubduction zone environment. The geochemistry of the ophiolite suggests that it is a fragment of oceanic lithosphere formed originally at a mid-ocean ridge (MOR) and then trapped above an intraoceanic subduction zone (SSZ), where the mantle peridotites were modified by boninitic melts. The Bangong–Nujiang suture zone is believed to mark the boundary between two blocks within Gondwanaland rather than to separate Gondwanaland from Eurasia.

SHRIMP dating of the Bangong Lake SSZ-type ophiolite: Constraints on the closure time of ocean in the Bangong Lake-Nujiang River, northwestern Tibet

The Bangong Lake ophiolite is located in the westernmost part of the Bangong Lake-Nujiang River suture zone. It is a tectonic melange consisting of numerous individual blocks of peridotite, pillowed and massive lavas and mafic dykes with SSZ-type ophiolitic geochemical affinity formed at the end of a Wilson circle. The SHRIMP U-Pb ages of the co-magmatic zircon domains from one gabbroic dyke (Sample 01Y-155) range from 162.5±8.6 Ma to 177.1±1.4 Ma with an average of 167.0±1.4 Ma (n = 12, MSWD = 1.2), suggesting that the subduction of the Bangong Lake Neo-Tethyan Ocean started before the Middle Jurassic. It is inferred that the tectonic transform from spreading to subduction of the Neo-Tethyan Ocean began before the Middle Jurassic in the Bangong Lake area.

40Ar/39Ar thermochronological evidence for formation and Mesozoic evolution of the northern-central segment of the Altyn Tagh fault system in the northern Tibetan Plateau

Research Article| September 01, 2005 40Ar/39Ar thermochronological evidence for formation and Mesozoic evolution of the northern-central segment of the Altyn Tagh fault system in the northern Tibetan Plateau Yu Wang; Yu Wang 1Geologic Laboratories Center and Department of Geology, China University of Geosciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Xuemin Zhang; Xuemin Zhang 2School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Erchie Wang; Erchie Wang 3Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Jinfeng Zhang; Jinfeng Zhang 4Department of Geology, China University of Geosciences, Beijing 100083, China Search for other works by this author on: GSW Google Scholar Qi Li; Qi Li 5Institute of Geology, China Seismological Bureau, Beijing 100029, China Search for other works by this author on: GSW Google Scholar Guihua Sun Guihua Sun 6Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China Search for other works by this author on: GSW Google Scholar Author and Article Information Yu Wang 1Geologic Laboratories Center and Department of Geology, China University of Geosciences, Beijing 100083, China Xuemin Zhang 2School of Geophysics and Information Technology, China University of Geosciences, Beijing 100083, China Erchie Wang 3Institute of Geology and Geophysics, Chinese Academy of Science, Beijing 100029, China Jinfeng Zhang 4Department of Geology, China University of Geosciences, Beijing 100083, China Qi Li 5Institute of Geology, China Seismological Bureau, Beijing 100029, China Guihua Sun 6Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China Publisher: Geological Society of America Received: 20 Jul 2004 Revision Received: 12 Dec 2004 Accepted: 10 Jan 2005 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2005) 117 (9-10): 1336–1346. https://doi.org/10.1130/B25685.1 Article history Received: 20 Jul 2004 Revision Received: 12 Dec 2004 Accepted: 10 Jan 2005 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Yu Wang, Xuemin Zhang, Erchie Wang, Jinfeng Zhang, Qi Li, Guihua Sun; 40Ar/39Ar thermochronological evidence for formation and Mesozoic evolution of the northern-central segment of the Altyn Tagh fault system in the northern Tibetan Plateau. GSA Bulletin 2005;; 117 (9-10): 1336–1346. doi: https://doi.org/10.1130/B25685.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract To better constrain the probable timing of formation and evolution of the Altyn Tagh sinistral strike-slip system in the Mesozoic, a 40Ar/39Ar thermochronological study has been carried out in the north-central segment of the Altyn Tagh fault system, the northern margin of the Qaidam Basin, and the eastern Kunlun orogenic belt. Muscovite, biotite, and K-feldspar separated from mylonite, granite, pegmatite, and metamorphic rocks have been analyzed. The range of 40Ar/39Ar data and structural evidence indicate that a peak metamorphic event in terranes bordering the Altyn Tagh fault system occurred between 450 and 420 Ma. At ca. 250–230 Ma there is evidence for initial sinistral strike-slip shearing. Sinistral strike-slip deformation occurred later along the Altyn Tagh fault system at 165–160 Ma and 100–89 Ma, respectively.Cooling histories in the northern margin of the Qaidam Basin and the eastern Kunlun orogenic belt show that these areas also experienced rapid cooling ca. 250–230 Ma, as was the case for the early Altyn Tagh fault system. This regional tectonic and cooling process indicates that the initial formation of the Altyn Tagh sinistral slip fault system occurred in latest Permian–Early Triassic time and was coupled with, or related to, suturing in the northern margin of the Qaidam Basin and the Kunlun orogenic belt. Cooling events along the Altyn Tagh fault system between 165 and 160 Ma and 100–89 Ma were accompanied by differential closure along the Bangong Lake–Nujiang suture zone in its eastern and western sectors during the Middle-Late Jurassic and Early Cretaceous, respectively (Zhao et al., 2001; Wang et al., 2002). You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Discovery of the boninite series volcanic rocks in the Bangong Lake ophiolite m�lange, western Tibet, and its tectonic implications

The boninite series volcanic rocks, mainly composed of basaltic andesite, andesitic lava breccia and andesite porphyrite, were recognized for the first time in the Bangong Lake ophiolite melange, western Tibet. These rocks have a strong boninitic affinity, with high SiO2 (55.61%–59.23%, weight percent), MgO (6.63%–13.08%, 9.13% on average (weight percent)), Al2O3/TiO2 ratios (36–54), Mg# (0.61–0.74), Ni (116 ppm on average) and Cr (354 ppm on average), low TiO2 (0.23%–0.39%, weight percent), and strong LILEs enrichment relative to the depleted HFSEs. Cl-chondrite normalized (La/Gd)N and (Gd/Yb)N ratios of about 1.70 and 0.83, respectively, produce prominent “U-shaped” normalized REE (rare earth element) patterns. Such a close compositional affinity to boninite indicates that these volcanic rocks were formed in a forearc setting produced by the intra-oceanic subduction.