bluuebunny/crossref_metadata_2025_split huggingface dataset:
Impacts and Exposed Lithospheric Mantle: A Way to Recognize large Terrestrial Impact basins?
Authors: OLDS Eric Peter 
Published: May 2019

AbstractOrientale size craters are not recognized on Earth nor expected for Phanerozoic and Proterozoic eons from conventional crater size frequency distributions (Ivanov et al., 2002). Here suggested are three such Phanerozoic craters, modified by plate tectonics, and tentatively correlated with extinction and “ophiolite obduction” events. Hypothesis testing is proposed and plate tectonics implications are discussed. Such basins might manifest:
circular to elliptical rims (or rim segments), with exposed lithospheric mantle, as strain markers for plate boundary motion;
thick ejecta near rim expressed as “ophiolitic melange”;
power law decay of ejecta thickness with radial distance from rim (McGetchin et al., 1973) and/or systematic azimuthal variation of ejecta thickness for low angle impacts (Schultz, 1999);
weathering resistant shocked mantle minerals (Bohor et al., 1990) in ejecta;• global spherule layer with PGE anomalies (Alvarez et al., 1980);
rim structures consistent with cratering mechanics (Melosh, 1989; Kenkmann, 2014);
impact melt basement (Grieve et al., 1992; Pierazzo et al. 2000) recording uniform cooling age and Earth's magnetic polarity of the time. Tentatively suggested Phanerozoic impact basins:
Yucatan Basin: Greater Antilles ophiolite rim – KPg Boundary? Maastrichtian ophiolite obduction in southeast Cuba (Iturralde‐Vinent et al., 2006).
Sulu Sea Basin: Palawan, Sabah etc. ophiolite rim – Middle Miocene Disruption? MM ophiolitic mélange emplacement in Sabah (Clennell, 1991).
Loyalty Basin: New Caledonia ophiolite and d'Entrecasteaux ridge rim – EO Boundary? EO ophiolite obduction in New Caledonia (Cluzel et al., 2012).
Petrogenesis and Tectonic Significance of the Cuobuzha Peridotite, Yarlung Zangbo Suture Zone, China
Authors: FENG Guangying , YANG Jingsui , DILEK Yildirim , LIU Fei , XIONG Fahui 
Published: May 2019

AbstractThe Yarlung Zangbo suture zone (YZSZ) in southern Tibet includes the remnants of Neo‐Tethyan oceanic lithosphere and marks a major suture between the Indian plate to the south and the Lhasa terrane of Tibet to the north. The upper mantle section of the Cuobuzha ophiolite in the northern subbelt of the western YZSZ comprises mainly clinopyroxene (cpx)‐rich and depleted harzburgites. Spinels in the cpx‐harzburgites show lower Cr# values (12.6–15.1) than the spinels in the harzburgites (26.1–34.5), and the cpx‐harzburgites display higher heavy rare earth element concentrations than the depleted harzburgites. The harzburgites have subchondritic Os isotopic compositions (0.11624–0.11699), yielding Re‐depletion model ages (TRD) ages from 1.8 to 1.7 Ga, indicating that the Cubuzha mantle underwent at least one ancient melt extraction event ca. 1.8‐1.7Ga; whereas the cpx‐harzburgites have suprachondritic 187Os/188Os ratios (0.12831–0.13125) with higher Re concentrations (0.380–0.575 ppb), indicating subsequent addition of Re following the last partial melting event that occurred during mid‐ocean ridge melt evolution processes. Although these geochemical and isotopic signatures suggest that both peridotite types in the ophiolite represent mid‐oceanic ridge–type upper mantle units, their melt evolution trends reflect different mantle processes. The cpx‐harzburgites formed from low‐degree partial melting of a primitive mantle source, and they were subsequently modified by melt‐rock interactions in a mid‐oceanic ridge environment. The depleted harzburgites, however, were produced by remelting of the cpx‐harzburgites, which later interacted with mid‐oceanic ridge basalt– or island‐arc tholeiite–like melts, possibly in a trench–distal backarc spreading center. Our new isotopic and geochemical data from the Cuobuzha peridotites confirm that the Neo‐Tethyan upper mantle had highly heterogeneous Os isotopic compositions as a result of multiple melt production and melt extraction events during its seafloor spreading evolution.
Geochemical Characteristics of the Gabbros from the Xinlin Ophiolite in the Great Xing'an Range, NE China
Authors: GOU Jun , SUN Deyou 
Published: May 2019

AbstractThe Xinlin ophiolite in NE China is generally considered to mark the suture between the Erguna and Xing'an blocks. Compared with the Maihantewula ophiolite and Jifeng‐Gaxian ophiolite in the southern and central parts of the Xinlin–Xiguitu suture zone, the Xinlin ophiolite in the northern part of the suture has not been as thoroughly investigated. Many studies acknowledge the indicators of the Xinlin ophiolite as a suture, but detailed studies of this unit are scarce. In the present work, we provide the geochemical data to constrain the origin of the gabbros in Xinlin ophiolites. The gabbros from the Xinlin ophiolites are texturally heterogeneous, ranging from fine‐grained aplitic to coarse‐grained pegmatitic. The fine‐grained gabbros have flat to slightly enriched LREE patterns, which are geochemically comparable to transitional (T‐MORB) and enriched mid‐ocean ridge basalt (E‐MORB). The pegmatite gabbros exhibit slightly LREE‐depleted patterns, similar to typical N‐MORB that derived from a depleted mantle source. Generally, gabbros from the Xinlin ophiolites are MORB‐like, but also have some arc characteristics such as high Th and low Ta concentrations. Such features is typical in Supra‐subduction zone (SSZ) type ophiolites. Our data, combined with other regional results, suggest that the geochemical signatures of the Xinlin gabbros that vary between arc‐like and MORB‐like were possibly indicative of their derivation from a subduction‐modified depleted mantle.
Carbon and Nitrogen Isotopic, and Mineral Inclusion Studies on the Diamonds from the Pozanti‐Karsanti Chromitite, Turkey
Authors: LIAN Dongyang , YANG Jingsui , WIEDENBECK Michael , ROCHOLL Alexander , DILEK Yildirim , WU Weiwei 
Published: May 2019

AbstractHe Pozanti‐Karsanti ophiolite (PKO) is one of the largest oceanic remnants in the Tauride belt, Turkey. Micro‐diamonds were recovered from the podiform chromitites, and these were investigated based on morphology, color, cathodoluminescence, nitrogen content, carbon and nitrogen isotopes, internal structure and inclusions. The diamonds recovered from the PKO are mainly mixed‐habit diamonds with sectors of different brightness under the cathodoluminescence images. The total δ13C range of the PKO diamonds ranges between −18.8 ‰ and −28.4 ‰, with a principle δ13C mode at −25 ‰. Nitrogen contents of the diamonds range from 7 to 541 μg/g with a mean value of 171 μg/g, and the δ15N values range from −19.1 ‰ to 16.6 ‰, with a δ15N mode of −9 ‰. Stacking faults and partial dislocations are commonly observed in the Transmission Electron Microscopy foils whereas inclusions are rather rare. Combinations of (Ca0.81Mn0.19)SiO3, NiMnCo‐alloy and nano‐size, quenched fluid phases were observed as inclusions in the PKO diamonds, confirming a natural origin of these diamonds. We believe that the δ13C‐depleted carbon signature of the PKO diamonds is a remnant of previously subducted crustal matter. These diamonds may have crystallized in metal‐rich melts in the asthenospheric mantle at depth below 250 km which were subsequently carried rapidly upward by asthenospheric melts/fliuds. We concluded that diamond‐bearing asthenospheric melts were likely involved in the formation of the Pozanti‐Karsanti podiform chromitite.
Limited Recycling of Crustal Osmium in Forearc Mantle During Slab Dehydration
Authors: LIU Chuanzhou , XU Yang , WU Fuyuan 
Published: May 2019

AbstractElevated 187Os/188Os ratios compared to ambient oceanic mantle, i.e.,187Os/188Os>0.13, have been reported for both arc lavas and mantle wedge xenoliths, which have been ascribed to the addition of crustal Os through slab dehydration or melting. By contrast, much lower 187Os/188Os ratios of spinels from Izu‐Bonin‐Mariana boninites indicate slight or no crustal Os was transferred from the slab to the forearc mantle. Here we report Os isotopic compositions of peridotites from New Caledonia ophiolites, which represent relics of a forearc mantle. Some New Caledonia peridotites are characterized by Os concentrations of <1 ppb, yet have187Os/188Os ratios comparable to the ambient oceanic mantle (i.e., 187Os/188Os<0.13). This confirms that little crustal Os was transported to the forearc mantle via slab dehydration. Contrasting Os isotopes between forearc peridotites and mantle wedge xenoliths may reflect the changing behavior of Os in diverse agents released from the descending slab as a function of depth, which is mainly controlled by the stability of sulfides in the slabs. During dehydration at shallow depths, sulfides keep stable and thus little Os is transported to the overlying mantle. In comparison, sulfides become unstable and tend to break down at deeper depths where slab melting or supercritical fluid generation occurs, and thus Os behaves like a mobile element.
Tectonic Implications of the Carboniferous Volcanic Rocks in the Eastern Junggar — Evidence from Zircon U‐Pb Ages and Geochemistry
Authors: WANG Chong , LUO Jinglan , CHEN Chunyong , HE Xianying , MA Shangwei , XU Xuelong , DAI Jingjing , LIU Yong 
Published: May 2019

AbstractWell Drilling shows that the volcanic rocks from the Carboniferous Batamayineishan Formation in the Eastern Junggar basin are mainly composed of volcaniclastic rocks (av. 52%) and volcanic lavas (32%), with a small amount of volcanic pyroclastic lavas (av. 11%). The volcanic lavas are basalt‐basaltic andesite‐andesite‐dacite assemblage. The LA‐ICP‐MS zircon U‐Pb dating of the andesite and the dacite yielded 325∼321 Ma and 310 Ma ages, respectively, which is of high agreement with the published age (300 Ma) of basalts from this Formation, it is implied that an important volcanic activity occurred in Junggar basin in the late Carboniferous. The lavas have low TiO2 and high Na2O, indicating a calc‐alkaline series. Geochemical data show that they are characterized by LREE‐enriched patterns with slightly negative Eu anomalies. The rocks have high large ion lithophile element (LILE), and low high field strength element (HFSE) concentrations, with strong negative Nb, Ta and Ti anomalies. From basic through intermediate to felsic, the depletions in Sr, Ti and P of the studied volcanic rocks increase gradually. These geochemical characteristics indicate that the volcanic rocks are magmatic evolution products attributed to partial melting of mantle‐derived spinelle lherzolite related to oceanic subduction in an island‐arc setting. In combination with the LA‐ICP‐MS zircon U‐Pb dating, it is inferred that subduction of the Junggar Ocean in eastern Junggar basin lasted to the Late Carboniferous. Consequently, the final closure of the Junggar Ocean occurred most likely after 310 Ma.
Sub‐mantle δ18O Zircons in Malani rhyolites: Clues for a Rodinia Linkage between South China and NW India
Authors: WANG Wei , CAWOOD Peter , ZHOU Meifu , PANDIT Manoj , XIA Xiaoping , ZHAO Junhong 
Published: May 2019

AbstractThe Malani Igneous Suite (MIS) in NW India represents one of the largest and well‐preserved Precambrian felsic igneous provinces, with minor mafic volcanics and dykes. The SIMS (Secondary Ion Mass Spectrometric) zircon U‐Pb geochronology yielded 776.8 ± 4.5 to 758.5 ± 6.9 Ma ages for rhyolites from Jodhpur region and Sindreth Basin while dacite sample from Punagarh Basin was dated to 760.5 ± 10 Ma. Zircons from rhyolitic and dacitic lavas have oxygen isotopic compositions that can be grouped into low δ18OV‐SMOW (4.12 to ‐1.11‰) and high (δ18O = 8.23‐5.12‰) categoroes, respectively. The low δ18O zircons have highly radiogenic Hf isotopic compositions (εHf(t)= +13.0 to +3.6) suggesting high temperature bulk cannibalization of upper level juvenile crust as the essential process for magma generation. Older than 800 Ma xenocrystic zircons in dacite have high δ18O values whereas 795 Ma ones have mantle‐like Hf‐O isotopic compositions, reflecting a significant shift in tectono‐thermal regime in NW India during 800‐780 Ma. A synchronous transition in the South China Block and Madagascar suggests a spatially and temporally linked geodynamic system. Geochemical data in combination with the new isotopic results point towards an overall convergent plate margin setting undergoing localized lithospheric extension. The NW India and South China blocks together with Madagascar and the Seychelles lay either along the periphery of Rodinia or off the supercontinent with the age of convergent plate margin magmatism coinciding with breakup of the supercontinent.
Babu (SW China)‐Cao Bang (NE Vietnam) Ophiolite Complex: Implications for Tectonic Evolution between South China and the Indochina Block
Authors: XIANG Zhongjin , YAN Quanren , XIA Wenjing , XIA Lei 
Published: May 2019

AbstractThe convergence process between South China and the Indochina Block is still controversial. A large number of igneous rocks scattered along the current China‐Vietnam border provide a good opportunity to investigate the tectonic evolution. Babu ophiolites, cropping out in the southeastern Yunnan province (SW China), consist primarily of metaperidotite, serpentinite, pillow basalt (metabasalt), gabbro, metadiabase. Most of them are fault contacted and strongly sheared, especially between metaperidotite/serpentinite and metabasalt. U‐Pb zircon analyses yield an Early Permian formation age of ∼278 Ma. Basalts and metagabbros show light rare earth elements (LREEs)‐depleted and heavy rare earth elements (HREEs)‐flat REE patterns, and large ion lithophile elements (LILEs)‐depleted primitive‐normalized spider diagrams without Nb‐Ta anomalies, which is similar to N‐MORB. Metaperidotites have low initial 187Os/188Os (0.122‐0.126) and γOs values, and indicate that they were derived from a depleted mantle source. Relative low (87Sr/86Sr)i and high εNd(t) values of basalts and metagabbros also support their DMM origin. The petrological, geochemical and isotope characteristics suggest that Babu ophiolites were N‐MORB‐type and represent remnants of an Early Permian oceanic crust. Mafic‐ultramafic rocks exposed in Cao Bang area (NE Vietnam) have recently been considered as dismembered Paleotethyan ophiolites instead of were genetically linked to the Emeishan Large Igneous Province. U‐Pb zircon analyses suggest an Early‐Middle Permian age (274 ±18 Ma) for the formation of ultramafic rocks. Both whole rock geochemistry and Cr‐spinel mineral chemistry show MORB‐like characteristics. Field observations suggest that Babu and Cao Bang ophiolite complex structurally overlie Middle‐Triassic deposits, and form a tectonic mélange zone. It developed from the subduction of a Paleotethyan subsidiary ocean basin between the South China and Indochina blocks until their collision..
Multi‐stage Melting Processes of Ophiolitic Chromitites from Purang Peridotite, the Western Yarlung‐Zangbo Suture Zone, Tibet
Authors: XIONG Fahui , YANG Jingsui , ROBINSON Paul T , XU Xiangzhe 
Published: May 2019

AbstractThe Purang ophiolite, which crops out over an area of about 600 km2 in the western Yarlung‐Zangbo suture zone, consists chiefly of mantle peridotite, pyroxenite and gabbro. The mantle peridotites are mostly harzburgite and minor lherzolite that locally host small pods of dunite. Some pyroxenite and gabbro veins of variable size occur in the peridotites, and most of them strike NW. On the basis of their mineral chemistry podiform chromitites are divided into high‐alumina (Cr# = 20‐60) (Cr# = 100*Cr/(Cr+Al)) and high‐chromium (Cr# = 60‐80) varieties (Thayer, 1970). Typically, only one type occurs in a given peridotite massif, although some ophiolites contain several massifs which can have different chromitite compositions. However, the Purang massif contains both high chrome and high alumina chromitites within a single mafic‐ultramafic body. Seven small, lenticular bodies of chromitite ore have been found in the harzburgite, with ore textures ranging from massive to disseminated to sparsely disseminated; no nodular ore has been observed. Individual ore bodies are 2‐6 m long, 0.5‐2 m wide and strike NW, parallel to the main structure of the ophiolite. Ore bodies 1 and 6 consist of Al‐rich chromitite (Cr# = 52‐55), whereas orebodies 2, 3, 4 and 5 are Cr‐rich varieties (Cr # = 63 to 89). In addition to magnesiochromite, all of the orebodies contain minor olivine, amphibole and serpentine. Mineral structures show that the peridotites experienced plastic deformation and partial melting. On the basis of magnesiochromite and olivine/clinopyroxene compositions two stages of partial melting are identified in the Purang peridotites, an early low‐partial melting event (about 8%), and a later high‐partial melting event (about 40%). We interpret the Al‐rich chromitites as the products of early MORB magmas, whereas the Cr‐rich varieties are thought to have been generated by the later SSZ melts..
Zircon U‐Pb Dating and Hf Isotope of the Metavolcanics, Gabbro and Plagiogranite in the Mianxian‐Lueyang Areas of Mianlue Belt
Authors: ZHANG Chengli 
Published: May 2019

AbstractThe Mianlue Belt is located in the central China and regarded as a tectonic mélange belt, representative of suture zone formed in the early Mesozoic between North and South China Blocks. However, its forming age has been controversial for a long time. This study provides the reliable LA‐ICPMS U‐Pb zircon dating and in‐situ Hf isotopes from the meta‐volcanics, gabbro and plagiogranite in this belt. Of which, two meta‐andesites yielded the ages of 934 Ma and 933 Ma, two meta‐dacites give the ages of 999 Ma and 873 Ma, and another plagiogranite define an age of 923 Ma, respectively, evidently older than those previously thoughted. Their Hf isotopes are quite coincident. The andesites have the εHf(t)= ‐0.03 ∼ +11.76 with the TDMC of 1032‐1629 Ma, εHf(t) = +9.81∼ +16.06 and the TDMC = 867‐1185 Ma for dacite and εHf(t) = +8.65 ∼ +16.66 and the TDMC = 805∼1123 Ma for plagiogranite, suggesting an important crustal growth in the early Neoproterozoic. In addition, the gabbro yielded younger ages of 224‐213 Ma and variable ages from 1225 Ma to 280 Ma in some inherited zircons, consistent with early Mesozoic mafic dykes in South Qinling belt. Their TDMC range from 1.2 to 2.7 Ga, indicating early‐middle Proterozoic crustal residence involved minor Neo‐Archean crustal materials. All new results lead us to propose that most of components in the Mianlue Belt were generated in the early Neoproterozoic and related to the subduction process in the northern margin of the Yangtze block, representative of an important juvenile crust growth in South Qinling during the Neoproterozoic.
The Metamorphic Evolution and Tectonic Significance of the Eclogite in the Sumdo Complex, Tibet, China
Authors: ZHANG Cong , BADER Thomas , VAN ROERMUND Herman , YANG Jingsui 
Published: May 2019

AbstractAs the main tectonic component of the Himalayan–Tibetan orogen, the Lhasa terrane has received much attention as it records the entire history of the orogeny. The occurrence of high pressure eclogite in the Sumdo complex in central Lhasa terrane has a significant bearing on the understanding of the Paleo‐Tethys subduction and plate itineration processes in this area. The petrological, geochemical and geochronological data from eclogite and associated blueschist and garnet‐bearing mica schist from Sumdo, Jilang and Bailang area have been briefly review to explore the origin and metamorphic evolution of this suture. Eclogites from the Sumdo complex have experienced low temperature, high pressure to ultrahigh pressure metamorphism, revealing a fast subduction and exhumation process in a typical oceanic subduction zone. The large P‐T span between different eclogites in the literature may be affected by the big error of unappropriated using geothermobarometry and may also because of slices of subducted blocks derived from different depths juxtapose together during exhumation. By summarizing the U‐Pb, Lu‐Hf and Sm‐Nd ages of eclogites, the eclogite facies metamorphism is likely to occur in early Triassic during 245‐225 Ma, but not the previously accepted late Permian at ca. 260 Ma by the reinterpretation of the former geochronological data from literature. The opening of Paleo‐Tethys Ocean between the Lhasa terrane initiate prior to ca. 280 Ma and ultimate closure to integrate the Lhasa terrane was no earlier than 225 Ma and may triggered by the initial subduction of Bangong‐Nujiang Tethys Ocean in the north.
High Accuracy Ground Magnetic Survey was Applied in the Khammouane Potash Deposit, the Lao P.D.R: An Efficient and Fast Exploration Model of Potash Deposits in Covered Areas
Authors: CUI Minli 
Published: May 2019

AbstractThe period and cost of mine exploration in new strange areas are very strict and very little geological data is available. The working area is usually covered by the exuberant vegetation, so the surface observation is very difficult and the working environment is very harsh. This paper introduces the application of high‐precision ground magnetic method to the rapid, efficient and low‐cost prospecting of favourable areas for mineralization in Khammouane Potash Deposit, the Lao P.D.R.
Analyses of the Compositional Characteristics and Sources of the Organochlorine Pesticides in the Surface Sediments of Guanghai Bay, Taishan City, Guangdong Province
Authors: HE Haijun , GAN Huayang , HE Jinxian , XIA Zhen 
Published: May 2019

AbstractOrganochlorine pesticides (OCPs) are a class of toxic and harmful persistent organic pollutants widely found in environment. Hexachlorocyclohexane (HCHs) and DDTs are two of the most widely used OCPs (Qiu et al., 2004), so it is important to find out their compositional characteristics and sources in surface sediments. Guanghai Bay is located in the south of Guanghai Bay Industrial Park in Taishan City, Guangdong Province. It borders Huangmaohai to the east and Zhenhai Bay to the west, covering an area of about 236 square kilometers. In this study, surface sediments were collected at 16 sites in Guanghai Bay (Fig. 1). After the surface sediments were pretreated, GC‐MS was used to analyze OCPs. A total of 14 OCPs were detected and their content was shown in Table 1. The concentration of ΣOCPs ranged between 0.507∼0.860ng·g‐1, with an average of 0.680 ng•g‐1. In general, the content of ΣOCPs was the highest at No. A12 site. The concentrations of these 14 detected OCPs ordered as dieldrin > epoxy heptachlor > P, P'‐DDD > γ‐HCH >endrin >aldrin > P, P'‐DDE >mirex >hexachlorobenzene >P, P'‐DDT > α‐HCH > δ‐HCH >β‐HCH > heptachlor.
When the Flames are Licking at the Door: Standing Mechanisms for Conflict Prevention
Authors: Nathan Laurie 
Published: May 2019

AbstractEnhancing the effectiveness of conflict prevention is a major preoccupation of the international community. This article focuses on operational prevention of conflict, which entails diplomatic efforts to avert imminent violence in crisis situations. The conventional understanding is that these efforts are short‐term and sporadic. In contrast, this article identifies and analyzes a type of operational prevention that has been institutionalized in order to engage in continuous preventive action in a particular conflict. I define ‘institutionalized operational prevention’ as a standing mechanism that aims to prevent a conflict from becoming violent and prevent low‐level violence from escalating into large‐scale violence. The article discusses a number of such mechanisms that have been successful in this regard, and offers an explanation for their success. Policymakers should consider establishing standing prevention mechanisms in other situations that have a persistent risk of large‐scale violence. Where structural reforms are required to reduce this risk but are politically unfeasible, the standing mechanisms may be the only viable means of avoiding violence.