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22 pages, 10150 KiB  
Review
A Review of Carboniferous-Triassic Tectonic-Magmatic Evolution of Luang Prabang–Loei Metallogenic Belt in Laos and Thailand and Implications for Gold–Copper Mineralization
by Linnan Guo, Khin Zaw, Shusheng Liu, Yongfei Yang, Fei Nie, Songyang Wu, Meifeng Shi, Chunmei Huang, Xiangfei Zhang, Huimin Liang, Xiangting Zeng and Siwei Xu
Geosciences 2025, 15(2), 68; https://doi.org/10.3390/geosciences15020068 - 16 Feb 2025
Viewed by 1245
Abstract
The Luang Prabang (Laos)–Loei (Thailand) metallogenic belt is located on the northwestern margin of the Indochina Block. It is one of the most important gold–copper metallogenic belts in Southeast Asia. This region underwent tectonic and magmatic evolution in the late Paleozoic-Mesozoic period within [...] Read more.
The Luang Prabang (Laos)–Loei (Thailand) metallogenic belt is located on the northwestern margin of the Indochina Block. It is one of the most important gold–copper metallogenic belts in Southeast Asia. This region underwent tectonic and magmatic evolution in the late Paleozoic-Mesozoic period within the Paleo-Tethys realm, resulting in complex metallogenic processes. Consequently, epithermal Au-Ag, porphyry-skarn Au-Cu, and hydrothermal vein-type gold deposits were formed. However, the genetic type of the vein-type gold deposits is still not fully understood. The relationship between the three types of gold deposits and the regional tectonic evolution has not been summarized up until today. We summarize the previous mineralization characteristics and exploration data of commonly known deposits and combine them with new evidence and ore deposit insights from our recent studies on the source and evolution of ore-forming fluids in the region. We confirm that the hydrothermal vein-type gold deposits in the belt are typical orogenic gold deposits. Based on previous regional tectonic-magmatic-metallogenic studies, metallogenic characteristics, and temporal and spatial distribution of three types of typical gold–copper deposits in the belt, we synthesize and establish a regional metallogenic model related to the subduction-closure of the Paleo-Tethys Ocean and subsequent continental–continental collision process, resulting in the formation of epithermal Au-Ag during the late Permian-early Triassic subduction, porphyry-skarn Au-Cu in the early–middle Triassic period during the closure of the ocean, and orogenic Au during the late Triassic collision. Since there are few reports on the geochemical characteristics of gold–copper deposits and their related magmatic rocks, the potential for gold–copper mineralization and their links to the magmatic rocks in the belt still needs further study. Full article
(This article belongs to the Special Issue Zircon U-Pb Geochronology Applied to Tectonics and Ore Deposits)
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34 pages, 11964 KiB  
Article
Formation and Tectonic Evolution of Ophiolites in the Sabah Area (Borneo, SE Asia)
by Zhiwen Tian, Youfeng Gao, Pujun Wang and Huafeng Tang
Minerals 2024, 14(11), 1078; https://doi.org/10.3390/min14111078 - 25 Oct 2024
Viewed by 3125
Abstract
Zircon U-Pb dating, rock geochemistry, Sr-Nd-Pb, and zircon Hf isotope analyses were conducted on the ultrabasic and basic rocks of ophiolites in the Sabah area (Borneo, SE Asia). The zircon U-Pb ages of ultrabasic and basic rocks range from 248 to 244 Ma, [...] Read more.
Zircon U-Pb dating, rock geochemistry, Sr-Nd-Pb, and zircon Hf isotope analyses were conducted on the ultrabasic and basic rocks of ophiolites in the Sabah area (Borneo, SE Asia). The zircon U-Pb ages of ultrabasic and basic rocks range from 248 to 244 Ma, indicating that the ophiolites already existed in the early Triassic. The rare earth elements of basic rocks in Central Sabah show N-MORB-type characteristics and E-MORB-type characteristics in the northwest and southeast. The εNd(t) values of basic rocks range from 3.66 to 8.73, and the εHf(t) values of zircon in ultrabasic rocks are between −10.2 and −6.1. Trace element analysis shows that the magmatic source was influenced by melts and fluids from the subducting plate of the Paleo-Tethys Ocean. The tectonic evolution of the Sabah area can be traced back to the Early Triassic. At that time, the fast subduction of the Paleo-Tethys Ocean plate and the retreating of the Paleo-Pacific plate resulted in the upwelling of mantle material in relatively small extensional settings, leading to the formation of the ophiolites. From the Jurassic to the Early Cretaceous, the Paleo-Pacific plate was intensely subducted, and the ophiolite intrusion in the Sabah area moved to the continental crust of South China or the Sundaland margin as fore-arc ophiolites. From the Late Cretaceous to the Miocene, with the expansion of the Proto-South China Sea and South China Sea oceanic crust, the ophiolites in the Sabah area drifted southward with microplate fragments and sutured with East Borneo. Full article
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24 pages, 9820 KiB  
Article
Characteristics of Deepwater Oil and Gas Distribution along the Silk Road and Their Controlling Factors
by Jianqiang Wang, Jie Liang, Qingfang Zhao, Jianwen Chen, Jian Zhang, Yong Yuan, Yinguo Zhang and Heping Dong
Water 2024, 16(2), 240; https://doi.org/10.3390/w16020240 - 10 Jan 2024
Cited by 6 | Viewed by 2484
Abstract
Deepwater regions have emerged as pivotal domains for global oil and gas exploration and development, serving as strategic alternatives to conventional resources. The Silk Road region is distinguished by its abundant oil and gas reserves and stands as a leading arena for worldwide [...] Read more.
Deepwater regions have emerged as pivotal domains for global oil and gas exploration and development, serving as strategic alternatives to conventional resources. The Silk Road region is distinguished by its abundant oil and gas reserves and stands as a leading arena for worldwide exploration and development in the oil and gas sector. Since 2012, a series of atmospheric fields have been discovered in the deep sea of the Luwuma Basin and the Tanzania Basin, with cumulative recoverable reserves reaching 4.4 × 1012 and 8.3 × 1011 m3, including multiple oil and gas fields ranking among the top ten global discoveries at that time. Profound advancements have been achieved in the exploration of deepwater oil and gas reserves along the Silk Road. However, deepwater oil and gas exploration presents challenges, such as high development costs and risks, leading to certain areas remaining underexplored and exhibiting a relatively low level of exploration activity, thereby hinting at considerable untapped potential. Deepwater sedimentary basins along the Silk Road predominantly adhere to a distribution pattern characterized as “one horizontal and one vertical”. The “horizontal” dimension refers to the deepwater basin grouping within the Neo-Tethys tectonic domain, primarily extending from east to west. Conversely, the “vertical” dimension denotes the deepwater basin grouping along the East African continental margin, predominantly extending from north to south. Recent discoveries of deepwater oil and gas reserves validate the presence of foundational elements within Silk Road basins conducive to the formation of substantial oil and gas reservoirs and the establishment of efficient migration pathways. Despite these achievements, exploration activities in deepwater oil and gas resources along the Silk Road remain relatively limited. Future exploration endeavors in deepwater regions will predominantly focus on identifying structural and lithological traps. In the deepwater areas of the Bay of Bengal, the emphasis is on lithological traps formed by Neogene turbidite sandstone deposits. In the deepwater regions of Pakistan, the focus shifts to lithological traps emerging from Neogene bio-reefs and river-channel sandstone accumulations. Along the deepwater coastline of East Africa, the focus is on lithological traps formed by nearshore Mesozoic–Cenozoic bio-reefs and seafloor turbidite sandstone formations. Within the deepwater regions of Southeast Asia, the primary objective is to locate large structural-type oil and gas fields. Analyzing the characteristics of oil and gas discoveries in deepwater areas aims to enhance the theory of the control of the formation of deepwater oil and gas, providing valuable insights for predicting future exploration directions. Full article
(This article belongs to the Special Issue Advances in Marine Sedimentation and Geological Processes)
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19 pages, 9374 KiB  
Article
Insights into the Crustal Evolution and Tungsten Mineralization of the West Cathaysia Block: Constraints from the Inherited Zircons from the Mesozoic Dengfuxian and Paleozoic Tanghu Plutons, South China
by Jingya Cao, Youyue Lu, Lei Liu, Jianming Fu, Guofeng Xu, Qianhong Wu, Shengxiong Yang, Xiaofei Qiu and Zunzun Zhang
Minerals 2023, 13(4), 550; https://doi.org/10.3390/min13040550 - 13 Apr 2023
Cited by 1 | Viewed by 1958
Abstract
The formation and evolution of the ancient continental crust are crucial issues in solid-earth geology which are commonly associated with global tectonic events and the formation of economically valuable magmatic-hydrothermal ore deposits. The Cathaysia Block, one of the ancient continents in Southeast Asia, [...] Read more.
The formation and evolution of the ancient continental crust are crucial issues in solid-earth geology which are commonly associated with global tectonic events and the formation of economically valuable magmatic-hydrothermal ore deposits. The Cathaysia Block, one of the ancient continents in Southeast Asia, can be subdivided into two parts: the West Cathaysia Block and the East Cathaysia Block. Unlike the East Cathaysia Block, no Precambrian rocks are exposed in the West Cathaysia Block, constraining further understanding of the formation and evolution of this block. In this study, a total of four hundred and thirty-three zircon U-Pb dating analyses and two hundred and eighteen Lu-Hf isotopic analyses on zircon grains from the Jurassic Dengfuxian granites and Ordovician Tanghu granites, Nanling Range, were carried out. LA-ICP-MS zircon U-Pb dating yields mean average 206Pb/238U ages of 152.6 ± 2.2 Ma (MSWD = 1.6) and 442.4 ± 1.7 Ma (MSWD = 3.8), which are regarded as the rock-forming age for the Jurassic Dengfuxian granites and Ordovician Tanghu granites, respectively. The 207Pb/206Pb ages of the inherited zircons from the Jurassic Dengfuxian granites and Ordovician Tanghu granites range from 522 Ma to 3395 Ma, hosting two major peaks at the 0.9–1.0 Ga and 2.4–2.5 Ga. In contrast to the East Cathaysia Block, the West Cathaysia Block lacks the age peak of 1.8–1.9 Ga, indicating that the West Cathaysia Block was not influenced by the assembly of the Columbia supercontinent in the Paleo-Proterozoic. In combination with the Lu-Hf isotopes, we proposed that the crust evolution of the West Cathaysia Block in Archean is dominated by juvenile crustal growth events, and dominated by the crustal reworking since the Proterozoic. The long duration of crustal reworking in the West Cathaysia Block resulted in the enrichment of lithophile elements (e.g., W, Sn, Nb, and Ta) in the crust of that region. Therefore, the Jurassic granites in the Nanling Range, which are mainly derived from the partial melting of Proterozoic basement rocks, became associated with large-scale tungsten polymetallic mineralization. Full article
(This article belongs to the Special Issue Critical Metals on Land and in the Ocean)
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14 pages, 3696 KiB  
Article
Application of Stable Isotopic Compositions of Rainfall Runoff for Evaporation Estimation in Thailand Mekong River Basin
by Jeerapong Laonamsai, Kimpei Ichiyanagi, Supapap Patsinghasanee, Kiattipong Kamdee and Nattapong Tomun
Water 2022, 14(18), 2803; https://doi.org/10.3390/w14182803 - 9 Sep 2022
Cited by 11 | Viewed by 2960
Abstract
The Mekong River Basin comprises approximately 38% of Southeast Asia. Our study area comprises the right-bank tributaries, which drain a substantial portion of Northeast Thailand. This study aimed to estimate the evaporative losses from streams during the 2013–2015 period. The normal and warm [...] Read more.
The Mekong River Basin comprises approximately 38% of Southeast Asia. Our study area comprises the right-bank tributaries, which drain a substantial portion of Northeast Thailand. This study aimed to estimate the evaporative losses from streams during the 2013–2015 period. The normal and warm El Niño–Southern Oscillation (ENSO) phases caused higher temperatures and low rainfall in the 2014–2015 period. The results show that the local meteoric water line for precipitation isotopes had seasonal variation due to variable precipitation. The enrichment of river isotopes indicated that streams lost an average of 4% of their water through evaporation. During the cooling ENSO phase, significant evaporation occurs due to the deep convection that typically occurs in tropical regions. In contrast, evaporation was low during the warm ENSO phase because of its geographic location. The El Niño year’s isotope values were significantly more enriched than the La Niña year’s, showing that precipitation and positive temperature anomalies affected the isotopic compositions in the continental basin. Furthermore, the deuterium excess helped distinguish the relative contributions of the wet and dry seasonal sources to the moisture origin, indicating that the predominant source of moisture is inland evaporation, with a small contribution from the ocean. Full article
(This article belongs to the Section Hydrology)
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17 pages, 4020 KiB  
Article
Phylogeography and Population History of Eleutharrhena macrocarpa (Tiliacoreae, Menispermaceae) in Southeast Asia’s Most Northerly Rainforests
by Shijie Song, Jianyong Shen, Shishun Zhou, Xianming Guo, Jinchao Zhao, Xinghui Shi, Zhiyong Yu, Qiangbang Gong, Shaohua You and Sven Landrein
Diversity 2022, 14(6), 437; https://doi.org/10.3390/d14060437 - 30 May 2022
Viewed by 2761
Abstract
The diversification of Tiliacoreae and the speciation of Eleutharrhena are closely linked to Southeast Asia’s most northerly rainforests which originate from the Himalayan uplift. Migration routes across biogeographical zones within the Asian clade, including those of Eleutharrhena, Pycnarrhena, and Macrococculus, [...] Read more.
The diversification of Tiliacoreae and the speciation of Eleutharrhena are closely linked to Southeast Asia’s most northerly rainforests which originate from the Himalayan uplift. Migration routes across biogeographical zones within the Asian clade, including those of Eleutharrhena, Pycnarrhena, and Macrococculus, and their population structures are still unexplored. We combine endocarp morphology, phylogenetic analyses, divergence time estimation, ancestral area reconstruction, as well as SCoT method to reconstruct the past diversification of Eleutharrhena macrocarpa and to understand their current distribution, rarity, and evolutionary distinctiveness. The disjunct, monospecific, and geographically restricted genera Eleutharrhena and Macrococculus both have a dry aril, a unique feature in Menispermaceae endocarps that further confirms their close relationship. Pycnarrhena and Eleutharrhena appeared during the end of the Oligocene c. 23.10 million years ago (Mya) in Indochina. Eleutharrhena speciation may be linked to climate change during this time, when humid forests became restricted to the northern range due to the Himalayan uplift. Differentiation across the Thai–Burmese range could have contributed to the isolation of the Dehong populations during the Miocene c. 15.88 Mya, when exchange between India and continental Asia ceased. Dispersal to the Lanping–Simao block and further differentiation in southeastern and southern Yunnan occurred during the Miocene, c. 6.82 Mya. The specific habitat requirements that led to the biogeographic patterns observed in E. macrocarpa contributed to a low genetic diversity overall. Population 1 from Dehong, 16 from Pu’er, and 20 from Honghe on the East of the Hua line have a higher genetic diversity and differentiation; therefore, we suggest that their conservation be prioritized. Full article
(This article belongs to the Special Issue Ecology, Evolution and Diversity of Plants)
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16 pages, 3463 KiB  
Article
Fire Impacts on Recruitment Dynamics in a Seasonal Tropical Forest in Continental Southeast Asia
by Kanokporn Kaewsong, Daniel J. Johnson, Sarayudh Bunyavejchewin and Patrick J. Baker
Forests 2022, 13(1), 116; https://doi.org/10.3390/f13010116 - 13 Jan 2022
Cited by 6 | Viewed by 2655
Abstract
The effects of forest fires on tree recruitment dynamics in tropical forests is important for predicting forest dynamics and ecosystem function in Southeast Asia. To our knowledge, no studies have examined the effects of fire intensity on community-level recruitment patterns in tropical forests [...] Read more.
The effects of forest fires on tree recruitment dynamics in tropical forests is important for predicting forest dynamics and ecosystem function in Southeast Asia. To our knowledge, no studies have examined the effects of fire intensity on community-level recruitment patterns in tropical forests due to the rarity of long-term observation datasets in fire-impacted tropical forests and the difficulty of quantifying fire intensity. We addressed two questions: (1) is tree recruitment among species affected by fire intensity? and if so, (2) are there specific plant functional traits associated with these responses? We used data from a long-term forest dynamics plot at the Huai Kha Khaeng (HKK) Wildlife Sanctuary in Thailand. The HKK plot occurs in a strongly seasonal tropical environment and has experienced several fires since its establishment in 1994. We found 46 tree species (52% of the 89 species analysed) showed evidence of reduced recruitment rates with increasing fire intensities during the most recent fire in 2005. Tree species in this flammable landscape have various leaf and wood functional traits associated with fire. Spatial and temporal variability in fire activity may lead to alterations in long-term taxonomic and functional composition of the forest due to selection on fire-related traits. Full article
(This article belongs to the Section Forest Ecology and Management)
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40 pages, 3809 KiB  
Review
Ecological-Health Risk Assessments of Heavy Metals (Cu, Pb, and Zn) in Aquatic Sediments from the ASEAN-5 Emerging Developing Countries: A Review and Synthesis
by Chee Kong Yap and Khalid Awadh Al-Mutairi
Biology 2022, 11(1), 7; https://doi.org/10.3390/biology11010007 - 21 Dec 2021
Cited by 31 | Viewed by 7717
Abstract
The ASEAN-5 countries (Malaysia, Indonesia, Thailand, Philippines, and Vietnam) of the Association of Southeast Asian Nations as a group is an ever-increasing major economy developmental hub in Asia besides having wealthy natural resources. However, heavy metal (HM) pollution in the region is of [...] Read more.
The ASEAN-5 countries (Malaysia, Indonesia, Thailand, Philippines, and Vietnam) of the Association of Southeast Asian Nations as a group is an ever-increasing major economy developmental hub in Asia besides having wealthy natural resources. However, heavy metal (HM) pollution in the region is of increasing environmental and public concern. This study aimed to review and compile the concentrations of Cu, Pb, and Zn in the aquatic sediments of the ASEAN-5 countries published in the literature from 1981 to February 2021. The mean values of Cu, Pb, and Zn in aquatic sediments were elevated and localized in high human activity sites and compared to the earth’s upper continental crust and reference values. Based on 176 reports from 113 publications, the ranges of concentrations (mg/kg dry weight) were 0.09–3080 for Cu, 0.37–4950 for Zn, and 0.07–2666 for Pb. The ecological risk (ER) values ranged from 0.02–1077 for Cu, 0.01–95.2 for Zn, and 0.02–784 for Pb. All reports (100%) showed the Zn ER values were categorized as being between ‘low potential ecological risk’ and ‘considerable potential ecological risk’. Almost all Cu ER values (97.7%) also showed similar ranges of the above two risk categories except for a few reports. The highest Cu level (3080 mg/kg dry weight) was reported from a mine-tailing spill in Marinduque Island of the Philippines with ‘very high ecological risk’. In addition, drainage sediments in the western part of Peninsular Malaysia were categorized as Cu ’high potential ecological risk’. Almost all reports (96%) showed Pb ER values categorized as between ‘low potential ecological risk’ and ‘moderate potential ecological risk’ except for a few reports. Six reports showed Pb ER values of ‘considerable potential ecological risk’, while one report from Semarang (Indonesia) showed Pb ER of ‘very high ecological risk’ (Pb level of 2666 mg/kg dry weight). For the ingestion and dermal contact pathways for sediments from the ASEAN-5 countries, all non-carcinogenic risk (NCR) values (HI values 1.0) for Cu, Pb, and Zn reflected no NCR. The ER and human health risk assessment of Cu, Pb, and Zn were compared in an integrative and accurate manner after we reassessed the HM data mentioned in the literature. The synthesis carried out in this review provided the basis for us to consider Cu, Pb, and Zn as being of localized elevated levels. This provided evidence for the ASEAN-5 group of countries to be considered as being a new socio-economic corridor. Beyond any reasonable doubt, an ever-increasing anthropogenic input of HMs is to be expected to a certain degree. We believe that this paper provides the most fundamental useful baseline data for the future management and sustainable development of the aquatic ecosystems in the region. Lastly, we claim that this review is currently the most up-to-date review on this topic in the literature. Full article
(This article belongs to the Special Issue Metals in Biology)
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17 pages, 5211 KiB  
Article
Determination of Lidar Ratio for Major Aerosol Types over Western North Pacific Based on Long-Term MPLNET Data
by Sheng-Hsiang Wang, Heng-Wai Lei, Shantanu Kumar Pani, Hsiang-Yu Huang, Neng-Huei Lin, Ellsworth J. Welton, Shuenn-Chin Chang and Yueh-Chen Wang
Remote Sens. 2020, 12(17), 2769; https://doi.org/10.3390/rs12172769 - 26 Aug 2020
Cited by 8 | Viewed by 4286
Abstract
East Asia is the most complex region in the world for aerosol studies, as it encounters a lot of varieties of aerosols, and aerosol classification can be a challenge in this region. In the present study, we focused on the relationship between aerosol [...] Read more.
East Asia is the most complex region in the world for aerosol studies, as it encounters a lot of varieties of aerosols, and aerosol classification can be a challenge in this region. In the present study, we focused on the relationship between aerosol types and aerosol optical properties. We analyzed the long-term (2005–2012) data of vertical profiles of aerosol extinction coefficients, lidar ratio (Sp), and other aerosol optical properties obtained from a NASA Micro-Pulse Lidar Network and Aerosol Robotic Network site in northern Taiwan, which frequently receives Asian continental outflows. Based on aerosol extinction vertical profiles, the profiles were classified into two types: type 1 (single-layer structure) and type 2 (two-layer structure). Fall season (October–November) was the prevailing season for the Type 1, whereas type 2 mainly happened in spring (March–April). In type 1, air masses normally originated from three regional sectors, i.e., Asia continental (AC), Pacific Ocean (PO), and Southeast Asia (SA). The mean Sp values were 39 ± 17 sr, 30 ± 12 sr, and 38 ± 18 sr for the AC, PO, and SA sectors, respectively. The Sp results suggested that aerosols from the AC sector contained dust and anthropogenic particles, and aerosols from the PO sector were most likely sea salts. We further combined the EPA dust event database and backward trajectory analysis for type 2. Results showed that Sp was 41 ± 14 sr and 53 ± 21 sr for dust storm and biomass-burning events, respectively. The Sp for biomass-burning events in type 2 showed two peaks patterns. The first peak occurred within range of 30–50 sr corresponding to urban pollutant, and the second peak occurred within range of 60–80 sr in relation to biomass burning. Finally, our study summarized the Sp values for four major aerosol types over northern Taiwan, viz., urban (42 ± 18 sr), dust (34 ± 6 sr), biomass-burning (69 ± 12 sr), and oceanic (30 ± 12 sr). Our findings provide useful references for aerosol classification and air pollution identification over the western North Pacific. Full article
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14 pages, 1657 KiB  
Article
Leaf Physiological Responses to Drought Stress and Community Assembly in an Asian Savanna
by Thuy T. Nguyen, Stefan K. Arndt and Patrick J. Baker
Forests 2019, 10(12), 1119; https://doi.org/10.3390/f10121119 - 8 Dec 2019
Cited by 5 | Viewed by 3027
Abstract
Deciduous dipterocarp forest (DDF) is the most extensive forest type in continental Southeast Asia, but across much of its range is functionally more similar to tropical savannas than tropical forests. We investigated water relations and drought responses of the four dominant tree species [...] Read more.
Deciduous dipterocarp forest (DDF) is the most extensive forest type in continental Southeast Asia, but across much of its range is functionally more similar to tropical savannas than tropical forests. We investigated water relations and drought responses of the four dominant tree species (two Shorea and two Dipterocarpus species) of the DDF in central Vietnam to determine how they responded to prolonged periods of drought stress. We quantified leaf water relations in nursery- and field-grown seedlings of the four species and conducted a dry-down experiment on 258 seedlings to study leaf water potential and morphological responses of the seedlings following the drought stress. The two Shorea and two Dipterocarpus species differed significantly in leaf water potential at turgor loss point and osmotic potential at full turgor, but they showed similar responses to drought stress. All species shed leaves and suffered from stem loss when exposed to water potentials lower than their turgor loss point (approximately −1.7 MPa for Dipterocarpus and −2.6 MPa for Shorea species). Upon rewatering, all species resprouted vigorously regardless of the degree of leaf or stem loss, resulting in only 2% whole-plant mortality rate. Our results suggest that none of the four deciduous dipterocarp species is drought tolerant in terms of their water relations; instead, they employ drought-adaptive strategies such as leaf shedding and vigorous resprouting. Given that all species showed similar drought avoidance and drought-adaptive strategies, it is unlikely that seasonal drought directly influences the patterns of species assembly in the DDF of Southeast Asia. Full article
(This article belongs to the Section Forest Ecophysiology and Biology)
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25 pages, 29258 KiB  
Article
Petrogenesis, Ore Mineralogy, and Fluid Inclusion Studies of the Tagu Sn–W Deposit, Myeik, Southern Myanmar
by Kyaw Thu Htun, Kotaro Yonezu, Aung Zaw Myint, Thomas Tindell and Koichiro Watanabe
Minerals 2019, 9(11), 654; https://doi.org/10.3390/min9110654 - 24 Oct 2019
Cited by 7 | Viewed by 9192
Abstract
Most of the granite-related Sn–W deposits in Myanmar are located in the Western Granitoid Province (WGP) of Southeast Asia. The Tagu deposit in the southern part of the WGP is a granite related Sn–W deposit. The biotite granite is composed of quartz, feldspars [...] Read more.
Most of the granite-related Sn–W deposits in Myanmar are located in the Western Granitoid Province (WGP) of Southeast Asia. The Tagu deposit in the southern part of the WGP is a granite related Sn–W deposit. The biotite granite is composed of quartz, feldspars (plagioclase, orthoclase, and microcline), and micas (muscovite and biotite) and belongs to S-type peraluminous granite. Abundances of large-ion lithophile elements (LILEs), such as Rb, K, and Pb, coupled with the deficiency of high-field-strength elements (HFSEs), such as Nb, P, and Ti, indicate that the parental magma for the Tagu granite was derived from the lower continental crust at syn-collisional setting. Mineralized veins consist of early-formed oxide ore minerals, such as cassiterite and wolframite, which were followed by the formation of sulfide minerals. Three main types of fluid inclusions were distinguished from the mineralized quartz veins hosted by granite and metasedimentary rocks: Type-A—two phases, liquid (L) + vapor (V) aqueous inclusions; Type-B—two phases, vapor (V) + liquid (L) vapor-rich inclusions; And type-C—three phases, liquid + CO2-liquid + CO2-vapor inclusions. Quartz in the veins hosted in granite corresponding with earlier deposition contains type-A, type-B, and type-C fluid inclusions, whereas that in the veins hosted in metasedimentary rocks corresponding with later deposition contains only type-A fluid inclusions. The homogenization temperatures of type-A inclusions range from 140 °C to 330 °C (mode at 230 °C), with corresponding salinities from 1.1 wt.% to 8.9 wt.% NaCl equivalent for quartz veins hosted in metasedimentary rocks, and from 230 °C to 370 °C (mode at 280 °C), with corresponding salinities from 2.9 wt.% to 10.6 wt.% NaCl equivalents for quartz veins hosted in granite. The homogenization temperatures of type-B vapor-rich inclusions in quartz veins in granite range from 310 °C to 390 °C (mode at 350 °C), with corresponding salinities from 6.7 wt.% to 12.2 wt.% NaCl equivalent. The homogenization temperatures of type-C H2O–CO2–NaCl inclusions vary from 270 °C to 405 °C (mode at 330 °C), with corresponding salinities from 1.8 wt.% to 5.6 wt.% NaCl equivalent. The original ascending ore fluid was probably CO2-bearing fluid which evolved into two phase fluid by immiscibility due to pressure drop in the mineralization channels. Furthermore, the temperature and salinities of two-phase aqueous fluids were later most likely decreased by the mixing with meteoric water. The salinities of the type-B vapor-rich inclusions are higher than those of the type-C CO2-rich inclusions, which may have resulted from CO2 separation from the fluids. The escape of gases can lead to an increase in the salinity of the residual fluids. Therefore, the main ore-forming mechanisms of the Tagu Sn–W deposit are characterized by fluid immiscibility during an early stage, and fluid mixing with meteoric water in the late stage at a lower temperature. Full article
(This article belongs to the Special Issue Magmatic–Hydrothermal Alteration and Mineralizing Processes)
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25 pages, 9096 KiB  
Article
Mesozoic Northward Subduction Along the SE Asian Continental Margin Inferred from Magmatic Records in the South China Sea
by Guanqiang Cai, Zhifeng Wan, Yongjian Yao, Lifeng Zhong, Hao Zheng, Argyrios Kapsiotis and Cheng Zhang
Minerals 2019, 9(10), 598; https://doi.org/10.3390/min9100598 - 30 Sep 2019
Cited by 22 | Viewed by 4863
Abstract
During the Mesozoic, Southeast (SE) Asia (including South China and the South China Sea (SCS)) was located in a transitional area between the Tethyan and Pacific geotectonic regimes. However, it is unclear whether geodynamic processes in the SE Asian continental margin were controlled [...] Read more.
During the Mesozoic, Southeast (SE) Asia (including South China and the South China Sea (SCS)) was located in a transitional area between the Tethyan and Pacific geotectonic regimes. However, it is unclear whether geodynamic processes in the SE Asian continental margin were controlled by Tethyan or paleo-Pacific Ocean subduction. Herein, we report ~124 Ma adakitic granodiorites and Nb-enriched basalts from the Xiaozhenzhu Seamount of the SCS. Granodiorites have relatively high Sr/Y (34.7–37.0) and (La/Yb)N (13.8–15.7) ratios, as well as low Y (9.67–9.90 μg/g) and Yb (0.93–0.94 μg/g) concentrations, typical of adakites. Their Sr/Y and (La/Yb)N values coupled with their relatively low initial 87Sr/86Sr ratios (0.70541–0.70551), relatively high K2O contents (3.31–3.38 wt%), high Th/La ratios (0.33–0.40), negative εNd(t) values (−3.62 to −3.52), and their variable zircon εHf(t) values (−3.8 to +5.2) indicate that these rocks were formed by melting of subducted oceanic crust and sediments. The Nb-enriched basalts show enrichment in high field strength elements (HFSE) and have εNd(t) values of +2.90 to +2.93, as well as relatively low initial 87Sr/86Sr ratios of 0.70341–0.70343, demonstrating that they were derived from a depleted-mantle (DM) source metasomatized by silicate magmas originating from melting of a subducted oceanic lithospheric slab. By combining our findings with data from other Late Mesozoic arc-related magmatic rocks and adakites from the broader study area, we propose a geotectonic model involving subduction of young oceanic lithosphere during the Late Jurassic and northward subduction of the proto-South China Sea (PSCS) along the SE Asian continental margin during the Early Cretaceous. This conceptual model better explains the two-period Mesozoic magmatism, commonly reported for the SE Asian continental margin. Full article
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31 pages, 2038 KiB  
Review
The Cynomolgus Macaque MHC Polymorphism in Experimental Medicine
by Takashi Shiina and Antoine Blancher
Cells 2019, 8(9), 978; https://doi.org/10.3390/cells8090978 - 26 Aug 2019
Cited by 24 | Viewed by 6927
Abstract
Among the non-human primates used in experimental medicine, cynomolgus macaques (Macaca fascicularis hereafter referred to as Mafa) are increasingly selected for the ease with which they are maintained and bred in captivity. Macaques belong to Old World monkeys and are phylogenetically [...] Read more.
Among the non-human primates used in experimental medicine, cynomolgus macaques (Macaca fascicularis hereafter referred to as Mafa) are increasingly selected for the ease with which they are maintained and bred in captivity. Macaques belong to Old World monkeys and are phylogenetically much closer to humans than rodents, which are still the most frequently used animal model. Our understanding of the Mafa genome has progressed rapidly in recent years and has greatly benefited from the latest technical advances in molecular genetics. Cynomolgus macaques are widespread in Southeast Asia and numerous studies have shown a distinct genetic differentiation of continental and island populations. The major histocompatibility complex of cynomolgus macaque (Mafa MHC) is organized in the same way as that of human, but it differs from the latter by its high degree of classical class I gene duplication. Human polymorphic MHC regions play a pivotal role in allograft transplantation and have been associated with more than 100 diseases and/or phenotypes. The Mafa MHC polymorphism similarly plays a crucial role in experimental allografts of organs and stem cells. Experimental results show that the Mafa MHC class I and II regions influence the ability to mount an immune response against infectious pathogens and vaccines. MHC also affects cynomolgus macaque reproduction and impacts on numerous biological parameters. This review describes the Mafa MHC polymorphism and the methods currently used to characterize it. We discuss some of the major areas of experimental medicine where an effect induced by MHC polymorphism has been demonstrated. Full article
(This article belongs to the Special Issue Major Histocompatibility Complex (MHC) in Health and Disease)
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21 pages, 31705 KiB  
Article
Towards Operational Monitoring of Forest Canopy Disturbance in Evergreen Rain Forests: A Test Case in Continental Southeast Asia
by Andreas Langner, Jukka Miettinen, Markus Kukkonen, Christelle Vancutsem, Dario Simonetti, Ghislain Vieilledent, Astrid Verhegghen, Javier Gallego and Hans-Jürgen Stibig
Remote Sens. 2018, 10(4), 544; https://doi.org/10.3390/rs10040544 - 2 Apr 2018
Cited by 52 | Viewed by 18140
Abstract
This study presents an approach to forest canopy disturbance monitoring in evergreen forests in continental Southeast Asia, based on temporal differences of a modified normalized burn ratio (NBR) vegetation index. We generate NBR values from each available Landsat 8 scene of a given [...] Read more.
This study presents an approach to forest canopy disturbance monitoring in evergreen forests in continental Southeast Asia, based on temporal differences of a modified normalized burn ratio (NBR) vegetation index. We generate NBR values from each available Landsat 8 scene of a given period. A step of ‘self-referencing’ normalizes the NBR values, largely eliminating illumination/topography effects, thus maximizing inter-comparability. We then create yearly composites of these self-referenced NBR (rNBR) values, selecting per pixel the maximum rNBR value over each observation period, which reflects the most open canopy cover condition of that pixel. The ΔrNBR is generated as the difference between the composites of two reference periods. The methodology produces seamless and consistent maps, highlighting patterns of canopy disturbances (e.g., encroachment, selective logging), and keeping artifacts at minimum level. The monitoring approach was validated within four test sites with an overall accuracy of almost 78% using very high resolution satellite reference imagery. The methodology was implemented in a Google Earth Engine (GEE) script requiring no user interaction. A threshold is applied to the final output dataset in order to separate signal from noise. The approach, capable of detecting sub-pixel disturbance events as small as 0.005 ha, is transparent and reproducible, and can help to increase the credibility of monitoring, reporting and verification (MRV), as required in the context of reducing emissions from deforestation and forest degradation (REDD+). Full article
(This article belongs to the Special Issue Remote Sensing of Forest Cover Change)
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22 pages, 7395 KiB  
Article
Forest Disturbances and Regrowth Assessment Using ALOS PALSAR Data from 2007 to 2010 in Vietnam, Cambodia and Lao PDR
by Stéphane Mermoz and Thuy Le Toan
Remote Sens. 2016, 8(3), 217; https://doi.org/10.3390/rs8030217 - 8 Mar 2016
Cited by 47 | Viewed by 8176
Abstract
This paper aims to develop a new methodology for monitoring forest disturbances and regrowth using ALOS PALSAR data in tropical regions. In the study, forest disturbances and regrowth were assessed between 2007 and 2010 in Vietnam, Cambodia and Lao People’s Democratic Republic. The [...] Read more.
This paper aims to develop a new methodology for monitoring forest disturbances and regrowth using ALOS PALSAR data in tropical regions. In the study, forest disturbances and regrowth were assessed between 2007 and 2010 in Vietnam, Cambodia and Lao People’s Democratic Republic. The deforestation rate in Vietnam has been among the highest in the tropics in the last few decades, and those in Cambodia and Lao are increasing rapidly. L-band ALOS PALSAR mosaic data were used for the detection of forest disturbances and regrowth, because L-band SAR intensities are sensitive to forest aboveground biomass loss. The methodology used here combines SAR data processing, which is particularly suited for change detection, forest detection and forest disturbances and regrowth detection using expectation maximization, which is closely related to fuzzy logic. A reliable training and testing database has been derived using AVNIR-2 and Google Earth images for calibration and validation. Efforts were made to apply masking areas that are likely to show different SAR backscatter temporal behaviors from the forests considered in the study, including mangroves, inundated forests, post-flooding or irrigated croplands and water bodies, as well as sloping areas and urban areas. The resulting forest disturbances and regrowth map (25-m resolution) indicates disturbance rates of −1.07% in Vietnam, −1.22% in Cambodia and −0.94% in Lao between 2007 and 2010, with corresponding aboveground biomass losses of 60.7 Tg, 59.2 Tg and 83.8 Tg , respectively. It is expected that the method, relying on free of charge data (ALOS and ALOS2 mosaics), can be applied widely in the tropics. Full article
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