Geochemistry and petrogenesis of Permian ultramafic-mafic complexes of the Jinping–Song Da rift (southeastern Asia)     

P.A. Balykin  G.V. Polyakov  A.E. Izokh  Tran Trong Hoa  Ngo Thi Phuong  Tran Quoc Hung  T.E. Petrova 《Russian Geology and Geophysics》2010,51(6):611-624

The Jinping–Song Da rift structure in the Emeishan Large Igneous Province is composed of Permian high- and low-Ti volcanic and volcanoplutonic ultramafic-mafic associations of different compositions and genesis. High-Ti picrites, picrobasalts, basalts, and dolerites are enriched in LREE and depleted in HREE and show low Al₂O₃/TiO₂ ratios (~4), commensurate ε_Nd(T) values (+0.5 to +1.1), and low (Th/Nb)_PM ratios similar to those of OIB-enriched mantle source. The established geochemical characteristics evidence that the parental melts of these rocks were generated from garnet lherzolite at the depths of garnet stability (~200 to 400 km). Later, high-Mg low-Ti volcanics (komatiites, komatiitic basalts, and basalts) and associating small peridotite-gabbro massifs and komatiite-basalt dikes were produced as a result of ~20% partial melting of depleted water-poor (≤0.03 wt.% H₂O) peridotite substratum from the hottest upper part of mantle plume at relatively shallow depths (100–120 km). The LREE-depleted komatiites and komatiitic basalts are characterized by low (Ce/Yb)_CH values, ¹⁸⁷Re/¹⁸⁸Os = 0.05–1.2, ⁸⁷Sr/⁸⁶Sr = 0.704–0.706, positive ε_Nd(T) values (+3 to +8), γ_Os = –0.5 to +0.9, and strong negative anomalies of Ba, K, and Sr on the spidergrams. The scarcer LREE-enriched komatiites, komatiitic basalts, and basalts vary greatly in chemical composition and values of ε_Nd(t) (+6.4 to –10.2), ⁸⁷Sr/⁸⁶Sr (0.706–0.712), and γ_Os (+14.8 to +56), which is due to the different degrees of crustal contamination of parental magmas. The Rb-Sr isotopic age of basaltic komatiite is 257 ± 24 Ma. The Re-Os age determined by analysis of 12 komatiite samples is 270 ± 21 Ma. These data agree with the age of flood basalts of the Emeishan Large Igneous Province. The komatiite-basalt complex of the Song Da rift is still the only Phanerozoic PGE-Cu-Ni-complex of this composition. The geochemistry of accompanying Cu-Ni-PGE-ores confirms their relationship with komatiite-basaltic magmatism.  相似文献   

Land tenure and REDD+: The good,the bad and the ugly     

Anne M. Larson  Maria Brockhaus  William D. Sunderlin  Amy Duchelle  Andrea Babon  Therese Dokken  Thu Thuy Pham  I.A.P. Resosudarmo  Galia Selaya  Abdon Awono  Thu-Ba Huynh 《Global Environmental Change》2013,23(3):678-689

A number of international donors, national governments and project proponents have begun to lay the groundwork for REDD+, but tenure insecurity – including the potential risks of land grabbing by outsiders and loss of local user rights to forests and forest land – is one of the main reasons that many indigenous and other local peoples have publicly opposed it. Under what conditions is REDD+ a threat to local rights, and under what conditions does it present an opportunity? This article explores these issues based on available data from a global comparative study on REDD+, led by the Center for International Forestry Research, which is studying national policies and processes in 12 countries and 23 REDD+ projects in 6 countries. The article analyses how tenure concerns are being addressed at both national and project level in emerging REDD+ programs. The findings suggest that in most cases REDD+ has clearly provided some new opportunities for securing local tenure rights, but that piecemeal interventions by project proponents at the local level are insufficient in the absence of broader, national programs for land tenure reform. The potential for substantial changes in the status quo appear unlikely, though Brazil – the only one with such a national land tenure reform program – offers useful insights. Land tenure reform – the recognition of customary rights in particular – and a serious commitment to REDD+ both challenge the deep-rooted economic and political interests of ‘business as usual’.  相似文献   

Sustainable groundwater development in the coastal Tra Vinh province in Vietnam under saltwater intrusion and climate change     

Van  Tuc Dang  Zhou  Yangxiao  Stigter  Tibor Y.  Van  Tuan Pham  Hong  Hai Dao  Uyen  Thanh Dong  Tran  Vuong Bui 《Hydrogeology Journal》2023,31(3):731-749

Three-dimensional transient groundwater flow and saltwater transport models were constructed to assess the impacts of groundwater abstraction and climate change on the coastal aquifer of Tra Vinh province (Vietnam). The groundwater flow model was calibrated with groundwater levels (2007–2016) measured in 13 observation wells. The saltwater transport model was compared with the spatial distribution of total dissolved solids. Model performance was evaluated by comparing observed and simulated groundwater levels. The projected rainfalls from two climate models (MIROC5 and CRISO Mk3.6) were subsequently used to simulate possible effects of climate changes. The simulation revealed that groundwater is currently depleted due to overabstraction. Towards the future, groundwater storage will continue to be depleted with the current abstraction regime, further worsening in the north due to saltwater intrusion from inland trapped saltwater and on the coast due to seawater intrusion. Notwithstanding, the impact from climate change may be limited, with the computed groundwater recharge from the two climate models revealing no significant change from 2017 to 2066. Three feasible mitigation scenarios were analyzed: (1) reduced groundwater abstraction by 25, 35 and 50%, (2) increased groundwater recharge by 1.5 and 2 times in the sand dunes through managed aquifer recharge (reduced abstraction will stop groundwater-level decline, while increased recharge will restore depleted storage), and (3) combining 50% abstraction reduction and 1.5 times recharge increase in sand dune areas. The results show that combined interventions of reducing abstraction and increasing recharge are necessary for sustainable groundwater resources development in Tra Vinh province.

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Lang Trang Cave (Northern Vietnam): Pleistocene Mammalian Locality with Gigantopithecus Finds     

Lopatin  A. V.  Golovachev  I. V.  Serdyuk  N. V.  Maschenko  E. N.  Vislobokova  I. A.  Dac  Le Xuan  Phuong  Pham Mai  Parkhaev  P. Yu.  Syromyatnikova  E. V. 《Doklady Earth Sciences》2022,504(2):372-379

Doklady Earth Sciences - Speleological, geological and paleontological characteristics of the Lang Trang cave in northern Vietnam are presented. Primates Gigantopithecus blacki von Koenigswald,...  相似文献   

Flood vulnerability and buildings’ flood exposure assessment in a densely urbanised city: comparative analysis of three scenarios using a neural network approach     

Pham  Quoc Bao  Ali  Sk Ajim  Bielecka  Elzbieta  Calka  Beata  Orych  Agata  Parvin  Farhana  Łupikasza  Ewa 《Natural Hazards》2022,113(2):1043-1081

Natural Hazards - Advances in the availability of multi-sensor, remote sensing-derived datasets, and machine learning algorithms can now provide an unprecedented possibility to predict flood events...  相似文献   

越南西北部Phan Si Pan地区Ngoi Chi岩组的锆石U-Pb年龄和Hf同位素组成     

HIEU Pham Trung 《地球学报》2015,36(6):755-760

本文对越南西北部Phan Si Pan地区变质地体中的一个Ngoi Chi片麻岩进行了锆石CL内部结构分析、LA-(MC)-ICP-MS锆石U-Pb定年和Hf同位素分析。CL图象和Th/U比值特征显示该片麻岩样品中的锆石主要为岩浆锆石,有少量窄的变质边。岩浆锆石的年龄为~2.9 Ga,表明该样品是越南西北部Phan Si Pan地区的基底岩石。它们的εHf(t)值为–4.70±0.92,二阶段Hf模式年龄为~3.5 Ga,表明其为更古老的(3.5 Ga)冥太古代地壳物质部分熔融作用形成。变质边部锆石给出了~1.8 Ga的年龄,表明变质作用发生在古元古代早期,Phan Si Pan地区在这一时期可能经历了一次重要的构造热事件。  相似文献   

Effects of riverbed incision on the hydrology of the Vietnamese Mekong Delta     

Doan Van Binh  Sameh A. Kantoush  Tetsuya Sumi  Nguyen Phuong Mai  Trieu Anh Ngoc  La Vinh Trung  Tran Dang An 《水文研究》2021,35(2):e14030

The hydrogeomorphology of the Vietnamese Mekong Delta (VMD) has been significantly altered by natural and anthropogenic drivers. In this study, the spatiotemporal changes of the flow regime were examined by analysing the long-term daily, monthly, annual and extreme discharges and water levels from 1980 to 2018, supported by further investigation of the long-term annual sediment load (from the 1960s to 2015), river bathymetric data (in 1998, 2014 and 2017) and daily salinity concentration (from the 1990s to 2015) using various statistical methods and a coupled numerical model. Then, the effects of riverbed incision on the hydrology were investigated. The results show that the dry season discharge (i.e., in March–June) of the Tien River increased by up to 23% from the predam period (1980–1992) to the postdam period (1993–2018) but that the dry season water level at My Thuan decreased by up to −46%. The annual mean and monthly water levels in June at Tan Chau and in January and June–October at My Thuan in the Tien River decreased statistically, even though the respective discharges increased significantly. These decreased water levels instead of the increased discharges were attributed to the accelerated riverbed incision upstream from My Thuan, which increased by more than three times, from a mean rate of −0.16 m/year (−16.7 Mm³/year) in 1998–2014 to −0.5 m/year (−52.5 Mm³/year) in 2014–2017. This accelerated riverbed incision was likely caused by the reduction in the sediment load of the VMD (from 166.7 Mt/year in the predam period to 57.6 Mt/year in the postdam period) and increase in sand mining (from 3.9 Mm³ in 2012 to 13.43 Mm³ in 2018). Collectively, the decreased dry season water level in the Tien River is likely one of the main causes of the enhanced salinity intrusion.  相似文献   

Torrential rainfall-triggered shallow landslide characteristics and susceptibility assessment using ensemble data-driven models in the Dongjiang Reservoir Watershed,China     

Dou  Jie  Yunus  Ali P.  Xu  Yueren  Zhu  Zhongfan  Chen  Chi-Wen  Sahana  Mehebub  Khosravi  Khabat  Yang  Yong  Pham  Binh Thai 《Natural Hazards》2019,97(2):579-609

Natural Hazards - This study investigated the characteristics of rainfall-triggered landslides during the Typhoon Bilis in the Dongjiang Reservoir Watershed, China. The comparative shallow...  相似文献   

Geochemistry and sediment in the main stream of the Ca River basin,Vietnam: weathering process,solute-discharge relationships,and reservoir impact     

Phuong  Ho Thi  Okubo  Kenji  Azhar Uddin  Md. 《中国地球化学学报》2019,38(5):627-641

Acta Geochimica - In this study, we investigated the chemical composition of dissolved solids in the Ca River basin, North-Central Vietnam. Water samples were collected from August 2017 to July...  相似文献   

Ionosphere probing with simultaneous GNSS radio occultations     

Pham  Viet-Cuong  Juang  Jyh-Ching 《GPS Solutions》2017,21(1):101-109

GPS Solutions - Radio occultation (RO) is a powerful technique for providing vertical profiles of refractivity, temperature, pressure, and water vapor of the neutral atmosphere and electron density...  相似文献