|
|
|
题名
|
作者
|
年代
|
出处
|
被引量
|
| 1 | The dilemma of the Jiaodong gold deposits: Are they unique?显示文摘The ca. 126-120 Ma Au deposits of the Jiaodong Peninsula, eastern China, define the country's largest gold province with an overall endowment estimated as >3000 t Au. The vein and disseminated ores are hosted by NE- to NNE-trending brittle normal faults that parallel the margins of ca. 165-150 Ma, deeply emplaced, lower crustal melt granites. The deposits are sited along the faults for many tens of kilometers and the larger orebodies are associated with dilatational jogs. Country rocks to the granites are Precambrian high-grade metamorphic rocks located on both sides of a Triassic suture between the North and South China blocks. During early Mesozoic convergent deformation, the ore-hosting structures developed as ductile thrust faults that were subsequently reactivated during Early Cretaceous 'Yanshanian' intracontinental extensional deformation and associated gold formation.Classification of the gold deposits remains problematic. Many features resemble those typical of orogenic Au including the linear structural distribution of the deposits, mineralization style, ore and alteration assemblages, and ore fluid chemistry. However, Phanerozoic orogenic Au deposits are formed by prograde metamorphism of accreted oceanic rocks in Cordilleran-style orogens. The Jiaodong deposits, in contrast, formed within two Precambrian blocks approximately 2 billion years after devolatilization of the country rocks, and thus require a model that involves alternative fluid and metal sources for the ores. A widespread suite of ca. 130-123 Ma granodiorites overlaps temporally with the ores, but shows a poor spatial association with the deposits. Furthermore, the deposit distribution and mineralization style is atypical of ores formed from nearby magmas. The ore concentration requires fluid focusing during some type of sub-crustal thermal event, which could be broadly related to a combination of coeval lithospheric thinning, asthenospheric upwelling, paleo-Pacific plate subduction, and seismicity along the continental-scale Tan-Lu fault. Possible ore genesis scenarios include those where ore fluids were produced directly by the metamorphism of oceanic lithosphere and overlying sediment on the subducting paleo-Pacific slab, or by devolatilization of an enriched mantle wedge above the slab. Both the sulfur and gold could be sourced from either the oceanic sediments or the serpentinized mantle. A better understanding of the architecture of the paleo-Pacific slab during Early Cretaceous below the eastern margin of China is essential to determination of the validity of possible models. | Richard J.Goldfarb M.Santosh | 2014 | Geoscience Frontiers2014，5，2： | 102 |
| 2 | Late Mesozoic basin and range tectonics and related magmatism in Southeast China显示文摘在迟了的中生代中间的 JurassicLate 白垩纪期间,盆和范围 tectonics 和 extensional 的联系 magmatism 代表构造设定在由于和平的板 subduction 的东南的中国是普遍的。盆 tectonics 由 post-orogenic 组成(类型我) 并且 intra 大陆人 extensional 盆(类型 II ) 。类型我盆在山麓和 intraland 发展了在期间对早侏罗记,纹理粗糙的陆上的碎屑状的沉积在被扔晚三叠纪。在 intra 大陆人期间形成的类型 II 盆外壳的变瘦并且被 grabens 和 half-grabens 的发展描绘。Graben 盆主要在中间的侏罗记期间被产生并且与 bimodal 火山作用被联系。在 half-grabens 的沉积与 rhyolitic 凝灰岩和熔岩被设置并且近来是在有优势的年龄的早白垩纪 CretaceousPaleogene 红床。范围由 granitoids 和 bimodal 组成暴烈的岩石, A 类型花岗石和屋顶类型变形核心建筑群。作者分析了 lithological, geochemical 和迟了的中生代火的岩石集合的 geochronological 特征并且在形成华南的盆和范围 tectonics 上建议了一些地球动力学的限制。类似的比较和在东方、西方的岸之间的盆和范围 tectonics 的差别和平被做,并且东南中国块的地球动力学的进化模型在迟了的中生代期间被讨论。学习结果建议华南在合拢的中生代前上开发了的在内的盆和范围岩层系上带子从自从迟了的中生代,西方的和平的板的 subduction 主要抑制的多相的构造进化被导出,在一个背弧 extensional 背景导致各种各样的 magmatism 的形成。它的 geodynamic 机制能在东方岸与盆和范围 tectonics 的作比较和平。在两岸之间的盆和范围 tectonics 的差别和平例如披风羽毛形成, extensional 和火的岩石集合和盆和范围 tectonics 的年龄可伸缩,主要被 Yellowstone 披风羽毛在太平洋的东方岸引起。 | Dezi Wang Liangshu Shu | 2012 | Geoscience Frontiers2012，3，2： | 60 |
| 3 | Isoplot R: A free and open toolbox for geochronology显示文摘This paper reviews the basic principles of radiometric geochronology as implemented in a new software package called Isoplot R, which was designed to be free, flexible and future-proof. Isoplot R is free because it is written in non-proprietary languages(R, Javascript and HTML) and is released under the GPL license. The program is flexible because its graphical user interface(GUI) is separated from the command line functionality, and because its code is completely open for inspection and modification. To increase future-proofness, the software is built on free and platform-independent foundations that adhere to international standards, have existed for several decades, and continue to grow in popularity.Isoplot R currently includes functions for U-Pb, Pb-Pb,40 Ar/39 Ar, Rb-Sr, Sm-Nd, Lu-Hf, Re-Os, U-Th-He,fission track and U-series disequilibrium dating. It implements isochron regression in two and three dimensions, visualises multi-aliquot datasets as cumulative age distributions, kernel density estimates and radial plots, and calculates weighted mean ages using a modified Chauvenet outlier detection criterion that accounts for the analytical uncertainties in heteroscedastic datasets. Overdispersion of geochronological data with respect to these analytical uncertainties can be attributed to either a proportional underestimation of the analytical uncertainties, or to an additive geological scatter term.Isoplot R keeps track of error correlations of the isotopic ratio measurements within aliquots of the same samples. It uses a statistical framework that will allow it to handle error correlations between aliquots in the future. Other ongoing developments include the implementation of alternative user interfaces and the integration of Isoplot R with other data reduction software. | Pieter Vermeesch | 2018 | Geoscience Frontiers2018，9，5： | 56 |
| 4 | Early Cretaceous overprinting of the Mesozoic Daqing Shan fold-and-thrust belt by the Hohhot metamorphic core complex,Inner Mongolia,China显示文摘中央内部蒙古的 Daqing 掸人(Mtns ) 的早白垩纪 Hohhot 变形核心建筑群(mcc ) 在暴露的最好和在北方中国 craton 的北边以内发展了的空间地孤立的 mccs 惊人的大多数之中。所有在一条晚古生代的 Andes 山脉风格的弧的地下室和可变年龄和构造 vergence 的到对面更旧的中生代 fold-and-thrust 带以内这些 mccs 被形成。主人 Hohhot 分开为至少 120 km 的沿着罢工距离在 Daqing 掸人的南部的边缘以内向南指责根。它在到北方的范围的几何学由干扰模式在之间是复杂的(1 ) 凸的主要、大规模 NW-SE-trending 和凹面指责折皱并且(2 ) 它的晚运动学的历史上合拢了分开的第二等的 ENE-WSW-trending antiforms 和 synforms。作为在 Whipple Mtns。加利福尼亚, Hohhot 主人分开不 Wernicke (1981 ) 是简单生根的类型;相反,它被孵化从一中间外壳砍地区,其顶在它的掘出的更低的板中在含碳的 metasedimentary 岩石以内作为 mylonitic 前面被保存。在现在的基础节硅质的暴烈的岩石标明日期的 40Ar39Ar 孤立 supradetachment 盆建议外壳的扩展在 ca 开始了。127 妈,尽管降低板的 mylonitic 岩石不暴露于侵蚀直到在 ca 以后。119 妈。在矿脉基卒下盘 mylonitic 片麻岩的角闪石,黑云母,和白云母的实质上同步的冷却显示很快速的发掘并且在 ca。122120 妈。与几份最近的报告相反,主人分开清楚地切到对面并且割下 Daqing 掸人低岬 fold-and-thrust 的更旧的、指导北方的戳表系上带子。合拢并且在它的 foredeep 阶层以内的指责戳的暗岩象 132.6 一样年轻 ??蔐 吗?? | Gregory A.Davis Brian J.Darby | 2010 | Geoscience Frontiers2010，1，1： | 47 |
| 5 | The Emeishan large igneous province:A synthesis显示文摘The late Permian Emeishan large igneous province(ELIP) covers ~0.3 x 106 km2 of the western margin of the Yangtze Block and Tibetan Plateau with displaced,correlative units in northern Vietnam(Song Da zone).The ELIP is of particular interest because it contains numerous world-class base metal deposits and is contemporaneous with the late Capitanian(~260 Ma) mass extinction.The flood basalts are the signature feature of the ELIP but there are also ultramafic and silicic volcanic rocks and layered maficultramafic and silicic plutonic rocks exposed.The ELIP is divided into three nearly concentric zones(i.e.inner,middle and outer) which correspond to progressively thicker crust from the inner to the outer zone.The eruptive age of the ELIP is constrained by geological,paleomagnetic and geochronological evidence to an interval of <3 Ma.The presence of picritic rocks and thick piles of flood basalts testifies to high temperature thermal regime however there is uncertainty as to whether these magmas were derived from the subcontinental lithospheric mantle or sub-lithospheric mantle(i.e.asthenosphere or mantle plume) sources or both.The range of Sr(I_(Sr) = 0.7040-0.7132),Nd(ε_(Nd)(t) ≈-14 to +8),Pb(^(206)Pb/^(204)Pb_1≈ 17.9-20.6) and Os(γ_(Os) =-5 to +11) isotope values of the ultramafic and mafic rocks does not permit a conclusive answer to ultimate source origin of the primitive rocks but it is clear that some rocks were affected by crustal contamination and the presence of near-depleted isotope compositions suggests that there is a sub-lithospheric mantle component in the system.The silicic rocks are derived by basaltic magmas/rocks through fractional crystallization or partial melting,crustal melting or by interactions between mafic and crustal melts.The formation of the Fe-Ti-V oxide-ore deposits is probably due to a combination of fractional crystallization of Ti-rich basalt and fluxing of C02-rich fluids whereas the Ni-Cu-(PGE) deposits are related to crystallization and crustal contamination of mafic or ultramafic magmas with subsequent segregation of a sulphide-rich portion.The ELIP is considered to be a mantle plume-derived LIP however the primary evidence for such a model is less convincing(e.g.uplift and geochemistry) and is far more complicated than previously suggested but is likely to be derived from a relatively short-lived,plume-like upwelling of mantle-derived magmas.The emplacement of the ELIP may have adversely affected the short-term environmental conditions and contributed to the decline in biota during the late Capitanian. | J.Gregory Shellnutt | 2014 | Geoscience Frontiers2014，5，3： | 50 |
| 6 | Subduction zone geochemistry显示文摘Crustal recycling at convergent plate boundaries is essential to mantle heterogeneity.However,crustal signatures in the mantle source of basaltic rocks above subduction zones were primarily incorporated in the form of liquid rather than solid phases.The physicochemical property of liquid phases is determined by the dehydration behavior of crustal rocks at the slab-mantle interface in subduction channels.Because of the significant fractionation in incompatible trace elements but the full inheritance in radiogenic isotopes relative to their crustal sources,the production of liquid phases is crucial to the geochemical transfer from the subducting crust into the mantle.In this process,the stability of specific minerals in subducting crustal rocks exerts a primary control on the enrichment of given trace elements in the liquid phases.For this reason,geochemically enriched oceanic basalts can be categorized into two types in terms of their trace element distribution patterns in the primitive mantle-normalized diagram.One is island arc basalts(IAB),showing enrichment in LILE,Pb and LREE but depletion in HFSE such as Nb and Ta relative to HREE,The other is ocean island basalts(OIB),exhibiting enrichment in LILE and LREE,enrichment or non-depletion in HFSE but depletion in Pb relative to HREE.In either types,these basalts show the enhanced enrichment of LILE and LREE with increasing their incompatibility relative to normal mid-ocean ridge basalts(MORB).The thermal regime of subduction zones can be categorized into two stages in both time and space,The first stage is characterized by compressional tectonism at low thermal gradients.As a consequence,metamorphic dehydration of the subducting crust prevails at forearc to subarc depths due to the breakdown of hydrous minerals such as mica and amphibole in the stability field of garnet and rutile,resulting in the liberation of aqueous solutions with the trace element composition that is considerably enriched in LILE,Pb and LREE but depleted in HFSE and HREE relative to normal MORB.This provides the crustal signature for the mantle sources of IAB.The second stage is indicated by extensional tectonism at high thermal gradients,leading to the partial melting of metamorphically dehydrated crustal rocks at subarc to postarc depths.This involves not only the breakdown of hydrous minerals such as amphibole,phengite and allanite in the stability field of garnet but also the dissolution of rutile into hydrous melts.As such,the hydrous melts can acquire the trace element composition that is significantly enriched in LILE,HFSE and LREE but depleted in Pb and HREE relative to normal MORB,providing the crustal signature for the mantle sources of OIB.In either case,these liquid phases would metasomatize the overlying mantle wedge peridotite at different depths,generating ultramafic metasomatites such as serpentinized and chloritized peridotites,and olivine-poor pyroxenites and hornblendites.As a consequence,the crustal signatures are transferred by the liquid phases from the subducting slab into the mantle. | Yong-Fei Zheng | 2019 | Geoscience Frontiers2019，10，4： | 47 |
| 7 | Rare earth elements:A review of applications, occurrence,exploration,analysis,recycling, and environmental impact显示文摘Rare earth elements(REE)include the lanthanide series elements(La,Ce,Pr,Nd,Pm,Sm,Eu,Gd,Tb,Dy.Ho,Er,Tm,Yb,and Lu)plus Sc and Y.Currently these metals have become very critical to several modern technologies ranging from cell phones and televisions to LED light bulbs and wind turbines.This article summarizes the occurrence of these metals in the Earth’s crust,their mineralogy,different types of deposits both on land and oceans from the standpoint of the new data with more examples from the Indian subcontinent.In addition to their utility to understand the formation of the major Earth reservoirs.multi-faceted updates on the applications of REE in agriculture and medicine including new emerging ones are presented.Environmental hazards including human health issues due to REE mining and large-scale dumping of e-waste containing significant concentrations of REE are summarized.New strategies for the future supply of REE including recent developments in the extraction of REE from coal fired ash and recycling from e-waste are presented.Recent developments in individual REE separation technologies in both metallurgical and recycling operations have been highlighted.An outline of the analytical methods for their precise and accurate determinations required in all these studies,such as,Xray fluorescence spectrometry(XRF),laser induced breakdown spectroscopy(LIBS),instrumental neutron activation analysis(INAA),inductively coupled plasma optical emission spectrometry(ICP-OES),glow discharge mass spectrometry(GD-MS),inductively coupled plasma mass spectrometry(including ICP-MS,ICP-TOF-MS,HR-ICP-MS with laser ablation as well as solution nebulization)and other instrumental techniques,in different types of materials are presented. | V.Balaram | 2019 | Geoscience Frontiers2019，10，4： | 42 |
| 8 | A review of mineral systems and associated tectonic settings of northern Xinjiang,NW China显示文摘在这份报纸我们在场在北 Xinjiang 的矿物质系统的评论, NW 中国,集中于 Tianshan,韦斯特和东方 Junggar 和 Altay orogenic 系上带子,所有哪个是更大的中央亚洲 Orogenic 带(CAOB ) 的部分。CAOB 是古老的 microcontinents,岛弧,海洋的 plateaux 和海洋的盘子的复杂大杂烩,它在早 Palaeozoic 被混合并且增大到早二叠的时间。CAOB 大杂烩的建立被罢工滑倒运动跟随并且由 intraplate magmatism 影响了,连接了到披风羽毛活动,最好由 250 个妈西伯利亚的陷井和 280 妈 Tarim 事件例示。在北 Xinjiang,有众多、经济地重要的矿物质系统。在这贡献,我们描述代表性的矿藏的一种选择,包括 subduction 相关的斑岩和 epithermal 沉积物, volcanogenic 巨大的硫醚和 skarn 系统。砍招待地区的 Au 矿脉可能是首先形成了在罢工滑倒期间侵入相关、随后重做变丑。Intraplate magmatism 导致了炮兵阵地同中心地 zoned (阿拉斯加人风格) maficultramafic 侵入,许多哪个主人 orthomagmatic 硫醚沉积物。在 Altay orogen 的伟晶岩的一条巨大的带,局部地招待世界级的稀罕金属沉积物。转动前面,招待沙岩的 U mineralisation 完成北 Xinjiang 岩层的富有的矿物质天赋。 | Franco Pirajno Reimar Seltmann Yongqiang Yang | 2011 | Geoscience Frontiers2011，2，2： | 39 |
| 9 | Estimation of soil erosion risk within a small mountainous sub-watershed in Kerala,India,using Revised Universal Soil Loss Equation(RUSLE) and geo-information technology显示文摘集成的全面方法论修订了通用土壤损失系统(GIS ) 技术被采用决定 forested 的土壤侵蚀危险的方程(RUSLE ) 模型和地理信息在 Kerala 的多山的亚分水岭,印度。年度土壤侵蚀率的空间模式被在一个光栅集成 geo 环境的变量获得基于的 GIS 方法。包括的 GIS 数据层,降雨 erosivity (R) ,土壤 erodability (K) ,斜坡长度和险峻,盖子管理(C) 和保存实践(P) 因素(LS ) 被计算决定他们的效果在区域的平均年度的土壤损失。年度土壤侵蚀的结果的地图在陡峭的方面斜坡上与与草土地区域,降级的森林和脱落森林的一种靠近的关系显示出 17.73 t h-1 y-1 的最大的土壤损失(与高 LS ) 。与 RUSLE 方法和 GIS 产生的空间侵蚀地图能在为土地在环境地敏感的多山的区域计划和管理导出策略用作有效输入。 | V.Prasannakumar H.Vijith S.Abinod N.Geetha | 2012 | Geoscience Frontiers2012，3，2： | 35 |
| 10 | Two stages of immiscible liquid separation in the formation of Panzhihua-type Fe-Ti-V oxide deposits,SW China显示文摘在 260 妈 Emeishan 大火的省(ELIP ) 的 Magmatic 氧化物沉积物, SW 中国和北越南,是 Fe, Ti 和 V 的重要来源。一些巨大的 magmatic Fe-Ti-V 氧化物沉积物例如 Panzhihua, Hongge,和 Baima 沉积物,很好在文学被描述并且在 Panxi 区域在分层的 mafic-ultramafic 侵入被招待,中央 ELIP。ELIP 相关的沉积物的一样的类型也远发生到南方并且在红河差错地区包括 Anyi 沉积物, Panzhihua 的大约 130 km 南方,和 Mianhuadi 沉积物。Anyi 沉积物是相对小的,但是同样在分层的 mafic 侵入被招待。Mianhuadi 沉积物有 260 妈的锆石 U-Pb 年龄并且与 ELIP 因此是同时期的。这存款易变地在指责的 Indosinian 造山运动和红河期间被变形。组合地, Mianhuadi 存款的磁铁矿比另外的存款的包含 Ti 和 V 的更小的数量,对以后的变态可能可归因。氧化物矿石存款的分发不与 ELIP 的 domal 结构有关。在 ELIP 的所有氧化物存款的一个主要特征是忍受氧化物的 gabbroic 侵入,黑花岗石 plutons 和 high-Ti 洪水暗岩的空间协会。因此,我们建议从一根披风羽毛的岩浆是进他们被发展进液体 immiscibility 的域形成二硅酸盐液体的一个浅岩浆房间的 emplaced,与一极其 Fe-Ti-rich gabbroic 作文和另外的黑花岗石。不能混合的 Fe-Ti-(P) 氧化物融化然后可以与 mafic 岩浆分开形成氧化物存款。这些存款从形成了的父母岩浆是在作文的可能的 Fe-Ti-rich picritic 并且比生产了 ELIP 的忍受硫化物的侵入的岩浆在更大的深度从充实的 asthenospheric 披风被导出。 | Mei-Fu Zhou Wei Terry Chen Christina Yan Wang Stephen A.Prevec Patricia Pingping Liu Geoffrey H.Howarth | 2013 | Geoscience Frontiers2013，4，5： | 35 |
| 11 | Multi-stage crustal growth and cratonization of the North China Craton显示文摘The North China Craton(NCC) has a complicated evolutionary history with multi-stage crustal growth,recording nearly all important geological events in the early geotectonic history of the Earth.Our studies propose that the NCC can be divided into six micro-blocks with >~3.0-3.8 Ga old continental nuclei that are surrounded by Neoarchean greenstone belts(CRB).The micro-blocks are also termed as highgrade regions(HGR) and are mainly composed of orthogneisses with minor gabbros and BIF-bearing supracrustal beds or lenses,all of which underwent strong deformation and metamorphism of granulite- to high-grade amphibolite-facies.The micro-blocks are,in turn,from east to west,the Jiaoliao(JL),Qianhuai(QH),Ordos(ODS),Ji’ning(JN) and Alashan(ALS) blocks,and Xuchang(XCH) in the south.Recent studies led to a consensus that the basement of the NCC was composed of different blocks/terranes that were finally amalgamated to form a coherent craton at the end of Neoarchean.Zircon U-Pb data show that TTG gneisses in the HGRs have two prominent age peaks at ca.2.9-2.7 and2.6-2.5 Ga which may correspond to the earliest events of major crustal growth in the NCC.Hafnium isotopic model ages range from ca.3.8 to 2.5 Ga and mostly are in the range of 3.0-2.6 Ga with a peak at2.82 Ga.Recent studies revealed a much larger volume of TTG gneisses in the NCC than previously considered,with a dominant ca.2.7 Ga magmatic zircon ages.Most of the ca.2.7 Ga TTG gneisses underwent metamorphism in 2.6-2.5 Ga as indicated by ubiquitous metamorphic rims around the cores of magmatic zircon in these rocks.Abundant ca.2.6-2.5 Ga orthogneisses have Hf-in-zircon and Nd wholerock model ages mostly around 2.9-2.7 Ga and some around 2.6-2.5 Ga,indicating the timing of protolith formation or extraction of the protolith magma was from the mantle.Therefore,it is suggested that the 2.6-2.5 Ga TTGs probably represent a coherent event of continental accretion and major reworking(crustal melting).As a distinct characteristic,nearly all GRBs in the NCC underwent amphibolite-facies metamorphism.Zircon U-Pb ages of metamorphosed GRB mafic rocks mainly show two peak ranges at ~2.6-2.5 and 2.8-2.7 Ga.The mafic rocks are commonly believed to be derived from metabasalts,it is therefore possible that the ages represent the time of metamorphism.The tectonic settings of the GRBs are still a problem.Their geochemical characteristics are,respectively,similar to back-arc basins,rifts,island arcs or suggest imprints of mantle plumes.BIFs occur in all GRBs but also in the HGRs.This metallogenic specificity is quite different from all Phanerozoic geotectonic settings.The-2.5 Ga metamorphic-magmatic event is stronger than in most other cratons in the world.How to understand the geological significance of the 2.5 Ga event? The following points are emphasized:(1)nearly all old rocks >2.5 Ga underwent metamorphism at ~2.52-2.5 Ga;(2) Archean basement rocks in the NCC experienced strong partial melting and migmatization;(3) granitoid rocks derived from partial melting include potassium granites,TTG granites and monzonites.These granitoids rocks intruded both the Archean greenstone belts and micro-blocks;(4) ~2.5 Ga mafic dikes(amphibolites),granitic dikes(veins) and syenitic-ultramafic dykes are also developed.Therefore,we suggest an assembly model that all micro-blocks in the NCC were welded together by late Archean greenstone belts at the end of the late Neoarchean.We also propose that the various micro-blocks were surrounded by small ocean basins,and the old continental crust and the oceanic crust were hotter than today.Subduction and collision were on much smaller scales as compared to the Phanerozoic plate tectonic regime,although the tectonic style and mechanisms were more or less similar.The formation of crustal melt granites is one of the processes of cratonization,inducing generation of stable upper and lower crustal layers.This process also generated an upper crust of more felsic composition and a lower crust of more mafic composition,due to molten residual materials and some underplated gabbros. | Mingguo Zhai | 2014 | Geoscience Frontiers2014，5，4： | 40 |
| 12 | Strategies towards statistically robust interpretations of in situ U-Pb zircon geochronology显示文摘Zircon U-Pb geochronology has become a keystone tool across Earth science,arguably providing the gold standard in resolving deep geological time.The development of rapid in situ analysis of zircon(via laser ablation and secondary ionization mass spectrometry) has allowed for large amounts of data to be generated in a relatively short amount of time and such large volume datasets offer the ability to address a range of geological questions that would otherwise remain intractable(e.g.detrital zircons as a sediment fingerprinting method).The ease of acquisition,while bringing benefit to the Earth science community,has also led to diverse interpretations of geochronological data.In this work we seek to refocus U-Pb zircon geochronology toward best practice by providing a robust statistically coherent workflow.We discuss a range of data filtering approaches and their inherent limitations(e.g.discordance and the reduced chi-squared;MSWD).We evaluate appropriate mechanisms to calculate the most geologically appropriate age from both ^(238)U/^(206)Pb and ^(207)Pb/^(206)Pb ratios and demonstrate the cross over position when chronometric power swaps between these ratios.As our in situ analytical techniques become progressively more precise,appropriate statistical handing of U-Pb datasets will become increasingly pertinent. | Christopher J.Spencer Christopher L.Kirkland Richard J.M.Taylor | 2016 | Geoscience Frontiers2016，7，4： | 36 |
| 13 | Assessment of soil erosion by RUSLE model using remote sensing and GIS-A case study of Nethravathi Basin显示文摘Soil erosion is a serious problem arising from agricultural intensification,land degradation and other anthropogenic activities.Assessment of soil erosion is useful in planning and conservation works in a watershed or basin.Modelling can provide a quantitative and consistent approach to estimate soil erosion and sediment yield under a wide range of conditions.In the present study,the soil loss model,Revised Universal Soil Loss Equation(RUSLE) integrated with GIS has been used to estimate soil loss in the Nethravathi Basin located in the southwestern part of India.The Nethravathi Basin is a tropical coastal humid area having a drainage area of 3128 km^2 up to the gauging station.The parameters of RUSLE model were estimated using remote sensing data and the erosion probability zones were determined using GIS.The estimated rainfall erosivity,soil erodibility,topographic and crop management factors range from 2948.16 to 4711.4 MJ/mm·ha^(-1)hr^(-1)/year,0.10 to 0.44 t ha^(-1)·MJ^(-1)·mm^(-1),0 to 92,774 and 0 to 0.63 respectively.The results indicate that the estimated total annual potential soil loss of about473,339 t/yr is comparable with the measured sediment of 441,870 t/yr during the water year 2002-2003.The predicted soil erosion rate due to increase in agricultural area is about 14,673.5 t/yr.The probability zone map has been derived by the weighted overlay index method indicate that the major portion of the study area comes under low probability zone and only a small portion comes under high and very high probability zone.The results can certainly aid in implementation of soil management and conservation practices to reduce the soil erosion in the Nethravathi Basin. | B.P.Ganasri H.Ramesh | 2016 | Geoscience Frontiers2016，7，6： | 36 |
| 14 | Fracture development in shale and its relationship to gas accumulation显示文摘有高石英,长石和碳酸盐的页岩,将有低泊松比率,高幼仔模量和高易碎物。作为结果,页岩是导致的在外部力量下面生产自然、导致的破裂。一般来说,在在页岩和在场的易碎的矿物质的体积的破裂开发之间有好关联。有高 TOC 或反常地高的压力的页岩开发得好破裂。页岩破裂开发也与全部的煤气的累积和免费煤气的体积显示出积极关联,即,页岩破裂越更好被开发,越 greater 煤气的累积并且因此越多更高煤气的生产。破裂为天然气和形成水提供迁居水管和累积空格,它为免费天然气的容量的增加是有利的。在页岩的更宽的破裂导致煤气的损失。在北美洲,从在页岩的高角度的破裂地区有页岩气体探索和高煤气的生产的高成功比率。在在四川盆的更低的古生代的海洋的器官的充满事的岩石中的好天然气表演或低收益制片人是仔细与在易碎的页岩的破裂开发的度有关。 | Wenlong Ding Chao Li Chunyan Li Changchun Xu Kai Jiu Weite Zeng Liming Wu | 2012 | Geoscience Frontiers2012，3，1： | 32 |
| 15 | Paleoproterozoic crustal evolution of the Hengshan-Wutai—Fuping region,North China Craton显示文摘An arguable point regarding the Neoarchean and Paleoproterozoic crustal evolution of the North China Craton(NCC)is whether the tectonic setting in the central belt during the mid-Paleoproterozoic(2.35-2.0 Ga)was dominated by an extensional regime or an oceanic subduction-arc regime.A review of the midPaleoproterozoic magmatism and sedimentation for the Hengshan-Wutai-Fuping region suggests that a back-arc extension regime was dominant in this region.This conclusion is consistent with the observation that the 2.35-2.0 Ga magmatism shows a typical bimodal distribution where the mafic rocks mostly have arc affinities and the acidic rocks mainly comprise highly-fractioned calc-alkaline to alkaline(or A-type)granites,and that this magmatism was coeval with development of extensional basins characteristic of transgressive sequences with volcanic interlayers such as in the Hutuo Group.Although the final amalgamation of the NCC was believed to occur at ~1.85 Ga,recent zircon U-Pb age dating for mica schist in the Wutai Group suggests a collisional event may have occurred at ~1.95 Ga.The metamorphic ages of ~1.85 Ga,obtained mostly from the high-grade rocks using the zircon U-Pb approach,most probably indicate uplifting and cooling of these high-grade terranes.This is because(i)phase modeling suggests that newly-grown zircon grains in highgrade rocks with a melt phase cannot date the age of peak pressure and temperature stages,but the age of melt crystallization in cooling stages;(ii)the metamorphic P-T paths with isobaric cooling under 6-7 kb for the Hengshan and Fuping granulites suggest their prolonged stay in the middle-lower crust;and(iii)the obtained metamorphic age data show a continuous distribution from 1.95 to 1.80 Ga.Thus,an alternative tectonic scenario for the Hengshan-Wutai-Fuping region involves:(i)formation of a proto-NCC at ~2.5 Ga;(ii)back-arc extension during 2.35-2.0 Ga resulting in bimodal magmatism and sedimentation in rifting basins on an Archean basement;(iii)a crustal thickening event in the extended region resulting in a kyanitetype metamorphism at ~1.95 Ga,and(iv) uplifting and cooling of the thickened crust from 1.93 to 1.80 Ga. | Chunjing Wei Jiahui Qian Xiwen Zhou | 2014 | Geoscience Frontiers2014，5，4： | 32 |
| 16 | How many sutures in the southern Central Asian Orogenic Belt:Insights from East Xinjiang-West Gansu(NW China)?显示文摘How ophiolitic mèlanges can be defined as sutures is controversial with regard to accretionary orogenesis and continental growth.The Chinese Altay,East junggar,Tianshan,and Beishan belts of the southern Central Asian Orogenic Belt(CAOB) in Northwest China,offer a special natural laboratory to resolve this puzzle.In the Chinese Altay,the Erqis unit consists of ophiolitic melanges and coherent assemblages,forming a Paleozoic accretionary complex.At least two ophiolitic melanges(Armantai,and Kelameili) in East Junggar,characterized by imbricated ophiolitic melanges,Nb-enriched basalts,adakitic rocks and volcanic rocks,belong to a Devonian-Carboniferous intra-oceanic island arc with some Paleozoic ophiolites,superimposed by Permian arc volcanism.In the Tianshan,ophiolitic melanges like Kanggurtag,North Tianshan,and South Tianshan occur as part of some Paleozoic accretionary complexes related to amalgamation of arc terranes.In the Beishan there are also several ophiolitic melanges,including the Hongshishan,Xingxingxia-Shibangjing,Hongliuhe-Xichangjing,and Liuyuan ophiolitic units.Most ophiolitic melanges in the study area are characterized by ultramafic,mafic and other components,which are juxtaposed,or even emplaced as lenses and knockers in a matrix of some coherent units.The tectonic settings of various components are different,and some adjacent units in the same melange show contrasting different tectonic settings.The formation ages of these various components are in a wide spectrum,varying from Neoproterozoic to Permian.Therefore we cannot assume that these ophiolitic melanges always form in linear sutures as a result of the closure of specific oceans.Often the ophiolitic components formed either as the substrate of intra-oceanic arcs,or were accreted as lenses or knockers in subduction-accretion complexes.Using published age and paleogeographic constraints,we propose the presence of (1) a major early Paleozoic tectonic boundary that separates the Chinese Altay-East Junggar multiple subduction systems of the southern Siberian active margin from those of the northern Tarim;and (2) a major Permian suture zone that separates the Tianshan-Beishan from the northern active margin of the Tarim Craton.These new observations and interpretations have broad implications for the architecture and crustal growth of central Asia and other ancient orogens as well. | Wenjiao Xiao Chunming Han Wei Liu Bo Wan Ji'en Zhang Songjian Ao Zhiyong Zhang Dongfang Song Zhonghua Tian Jun Luo | 2014 | Geoscience Frontiers2014，5，4： | 31 |
| 17 | A new method of discriminating different types of post-Archean ophiolitic basalts and their tectonic significance using Th-Nb and Ce-Dy-Yb systematics显示文摘In this paper,a new discrimination diagram using absolute measures of Th and Nb is applied to postArchean ophiolites to best discriminate a large number of different ophiolitic basalts.This diagram was obtained using>2000 known ophiolitic basalts and was tested using w560 modern rocks from known tectonic settings.Ten different basaltic varieties from worldwide ophiolitic complexes have been examined.They include two basaltic types that have never been considered before,which are:(1)medium-Ti basalts(MTB)generated at nascent forearc settings;(2)a type of mid-ocean ridge basalts showing garnet signature(G-MORB)that characterizes Alpine-type(i.e.,non volcanic)rifted margins and ocean-continent transition zones(OCTZ).In the Th-Nb diagram,basalts generated in oceanic subductionunrelated settings,rifted margins,and OCTZ can be distinguished from subduction-related basalts with a misclassi fi cation rate<1%.This diagram highlights the chemical variation of oceanic,rifted margin,and OCTZ basalts from depleted compositions to progressively more enriched compositions re fl ecting,in turn,the variance of source composition and degree of melting within the MORB-OIB array.It also highlights the chemical contributions of enriched(OIB-type)components to mantle sources.Enrichment of Th relative to Nb is particularly effective for highlighting crustal input via subduction or crustal contamination.Basalts formed at continental margin arcs and island arc with a complex polygenetic crust can be distinguished from those generated in intra-oceanic arcs in supra-subduction zones(SSZ)with a misclassi fi cation rate<1%.Within the SSZ group,two sub-settings can be recognized with a misclassi fi cation rate<0.5%.They are:(1)SSZ in fl uenced by chemical contribution from subductionderived components(forearc and intra-arc sub-settings)characterized by island arc tholeiitic(IAT)and boninitic basalts;(2)SSZ with no contribution from subduction-derived components(nascent forearc sub-settings)characterized by MTBs and depleted-MORBs.Two additional discrimination diagrams are proposed:(1)a Dy-Yb diagram is used for discriminating boninite and IAT basalts;(2)a Ce/Yb-Dy/Yb diagram is used for discriminating G-MORBs and normal MORBs.The proposed method may effectively assist in recovering the tectonic af fi nity of ancient ophiolites,which is fundamental for establishing the geodynamic evolution of ancient oceanic and continental domains,as well as orogenic belts. | Emilio Saccani | 2015 | Geoscience Frontiers2015，6，4： | 34 |
| 18 | Multivariate adaptive regression splines and neural network models for prediction of pile drivability显示文摘Piles are long, slender structural elements used to transfer the loads from the superstructure through weak strata onto stiffer soils or rocks. For driven piles, the impact of the piling hammer induces compression and tension stresses in the piles. Hence, an important design consideration is to check that the strength of the pile is sufficient to resist the stresses caused by the impact of the pile hammer. Due to its complexity, pile drivability lacks a precise analytical solution with regard to the phenomena involved.In situations where measured data or numerical hypothetical results are available, neural networks stand out in mapping the nonlinear interactions and relationships between the system's predictors and dependent responses. In addition, unlike most computational tools, no mathematical relationship assumption between the dependent and independent variables has to be made. Nevertheless, neural networks have been criticized for their long trial-and-error training process since the optimal configuration is not known a priori. This paper investigates the use of a fairly simple nonparametric regression algorithm known as multivariate adaptive regression splines(MARS), as an alternative to neural networks, to approximate the relationship between the inputs and dependent response, and to mathematically interpret the relationship between the various parameters. In this paper, the Back propagation neural network(BPNN) and MARS models are developed for assessing pile drivability in relation to the prediction of the Maximum compressive stresses(MCS), Maximum tensile stresses(MTS), and Blow per foot(BPF). A database of more than four thousand piles is utilized for model development and comparative performance between BPNN and MARS predictions. | Wengang Zhang Anthony T.C.Goh | 2016 | Geoscience Frontiers2016，7，1： | 34 |
| 19 | State-of-the-art review of soft computing applications in underground excavations显示文摘Soft computing techniques are becoming even more popular and particularly amenable to model the complex behaviors of most geotechnical engineering systems since they have demonstrated superior predictive capacity,compared to the traditional methods.This paper presents an overview of some soft computing techniques as well as their applications in underground excavations.A case study is adopted to compare the predictive performances of soft computing techniques including eXtreme Gradient Boosting(XGBoost),Multivariate Adaptive Regression Splines(MARS),Artificial Neural Networks(ANN),and Support Vector Machine(SVM) in estimating the maximum lateral wall deflection induced by braced excavation.This study also discusses the merits and the limitations of some soft computing techniques,compared with the conventional approaches available. | Wengang Zhang Runhong Zhang Chongzhi Wu Anthony Teck Chee Goh Suzanne Lacasse Zhongqiang Liu Hanlong Liu | 2020 | Geoscience Frontiers2020，11，4： | 33 |
| 20 | Prediction of undrained shear strength using extreme gradient boosting and random forest based on Bayesian optimization显示文摘Accurate assessment of undrained shear strength(USS)for soft sensitive clays is a great concern in geotechnical engineering practice.This study applies novel data-driven extreme gradient boosting(XGBoost)and random forest(RF)ensemble learning methods for capturing the relationships between the USS and various basic soil parameters.Based on the soil data sets from TC304 database,a general approach is developed to predict the USS of soft clays using the two machine learning methods above,where five feature variables including the preconsolidation stress(PS),vertical effective stress(VES),liquid limit(LL),plastic limit(PL)and natural water content(W)are adopted.To reduce the dependence on the rule of thumb and inefficient brute-force search,the Bayesian optimization method is applied to determine the appropriate model hyper-parameters of both XGBoost and RF.The developed models are comprehensively compared with three comparison machine learning methods and two transformation models with respect to predictive accuracy and robustness under 5-fold cross-validation(CV).It is shown that XGBoost-based and RF-based methods outperform these approaches.Besides,the XGBoostbased model provides feature importance ranks,which makes it a promising tool in the prediction of geotechnical parameters and enhances the interpretability of model. | Wengang Zhang Chongzhi Wu Haiyi Zhong Yongqin Li Lin Wang | 2021 | Geoscience Frontiers2021，12，1： | 33 |
您所在的机构暂未开通此部分的功能，请联系管理员