重庆秀山小茶园地区南华纪大塘坡组沉积环境与锰矿产出规律

在系统分析重庆秀山小茶园锰矿区大批钻孔数据资料的基础上,基于野外地质调查和室内沉积学、地球化学等分析得出,盆地中心相的沉积物厚度大,TOC、U、Mo、V、δ34S_py的含量高,草莓状黄铁矿丰富,指示了缺氧的水体条件,且锰矿的品位和厚度大。向盆地边缘相、斜坡相,沉积物厚度减小,TOC、U、Mo、V、δ34S_py含量降低,指示水体缺氧程度减弱,同时锰矿的品位和厚度减小。锰矿体厚度的变化与含锰岩系厚度的变化规律一致,二者呈正相关关系。小茶园矿区矿体展布方向与小茶园次级地堑盆地长轴方向基本一致,为NE60°左右。因此,小茶园矿区锰矿床矿体产出受到次级地堑盆地和沉积相带的控制,缺氧的盆地中心相成矿最佳,其次为盆地边缘相,斜坡相成矿较差。     

古海洋氧化还原地球化学指标研究新进展

古海洋氧化还原条件的恢复一直是地学界的研究热点。许多指标可以用来指示古海洋沉积岩(物)的氧化还原条件。其中地球化学和矿物学方法历来是研究古海洋氧化还原条件的主要手段,前人工作主要集中在单个种类指标(沉积学、矿物学、地球化学等)的单方面研究,缺乏系统研究。但沉积物中的氧化还原指标受很多因素的影响,用单个指标来指示水体的氧化还原条件存在不确定性。主要通过主量元素(总有机碳TOC、有机碳和磷的摩尔比Corg∶P),氧化还原敏感的微量元素(U、V、Mo),黄铁矿类型和草莓状黄铁矿粒径分布以及同位素(黄铁矿硫同位素δ34Spyrite、钼同位素δ98 Mo、铀同位素δ238 U)等指标的综合运用来区分硫化、缺氧、次氧化以及氧化等水体条件。在硫化水体中,氧化还原敏感元素和TOC含量均大量富集,尤其是Mo的富集系数(MoEF)比U的富集系数(UEF)更大(MoEFUEF),有机碳和磷的摩尔比(Corg∶P)也呈现高值;黄铁矿几乎全部呈草莓状,很少出现自形晶,草莓状黄铁矿平均粒径小(常小于5μm)且变化不大,δ34Spyrite值偏负,δ98 Mo值和海水同位素值接近,约为+2.3‰,δ238 U值为+0.2‰,高于海水的同位素值(-0.41‰)。水体环境为氧化的条件下,氧化还原敏感的元素和TOC的量都很缺乏,有机碳和磷的摩尔比(Corg∶P)出现低值,黄铁矿很少,且主要以自形晶的形式出现,平均粒径很大,黄铁矿中的δ34Spyrite值偏正,δ98 Mo值偏负,为-0.7‰,δ238 U值为-0.65‰。在缺氧和次氧化水体环境中,各种指标介于硫化和氧化环境之间,氧化还原敏感元素和TOC含量适中,U相对比Mo富集(UEFMoEF),黄铁矿以草莓状为主,有部分的自形晶出现,黄铁矿平均粒径较大,而且变化范围较大,黄铁矿中的δ34Spyrite值、δ98 Mo值以及δ238 U值均介于氧化和硫化环境之间。最后,还提出在分析古海洋的氧化还原条件时,要综合考虑多种影响因素,清晰认识到每个指标的适用性和局限性,并指出了存在的问题和不足。     

湘西下寒武统牛蹄塘组黑色岩系的微量元素地球化学特征

为探讨下寒武统黑色岩系在深水区域的沉积环境及其伴生的Ni-Mo多金属富集层的金属元素来源,对湘西寒武纪初期盆地相区龙鼻嘴剖面进行系统采样,分析了样品中干酪根的微量元素含量和全岩V、U、Mo与TOC含量并就微量元素比值与TOC关系进行了探讨。结果显示,干酪根中的Th/U、V/Sc和V/Cr值在剖面上均具有相似的变化规律,V、U和Mo与TOC的相关性可知剖面沉积过程中存在硫化环境,Ni-Co-Zn三角图解中多数样品分布于热水沉积区域。初步推断剖面下部的NiMo多金属富集层,其具有微量元素明显富集和碳同位素较大负值的特征,可作为地层对比的标志;寒武纪初始阶段深水区域可能处于短暂的硫化环境,伴随着沉积环境的充氧之后变为广泛的厌氧环境;黑色岩系沉积过程中有热液活动参与,Ni-Mo多金属富集层中部分元素的极度富集可能是还原的海水和海底热液共同作用的结果。     

鄂西-黔东北地区早寒武世有机质富集机理对比研究

寒武纪早期地球环境和生物面貌发生了巨大变化，中上扬子广泛发育的富有机质沉积是重要的烃源岩。了解这套烃源岩的形成与古地理背景、古气候和古海洋之间的耦合关系，明确不同沉积环境有机质富集机理的差异有助于我们认识环境与资源的内在联系，为资源潜力分析提供地质依据。本研究以鄂西-黔东北地区早寒武世沉积剖面为研究对象，通过岩石学、有机地球化学(岩石热解、干酪根碳同位素和总有机碳)和无机地球化学(主量、微量元素和全岩矿物X衍射)方法，识别了烃源岩特征，对比分析了内陆架盆地(或台盆相)和斜坡相有机质富集的主控因素。结果显示，研究区早寒武世有机质已高过成熟，干酪根类型以Ⅰ型为主。内陆架盆地/台盆相的鸭子口剖面Al含量，Ba、Cu、Zn和Ni等营养元素含量，以及黏土含量在有机质富集段无明显变化；Mo、U和V等氧化还原敏感元素和TOC含量在水井沱组下段较高，向上逐渐减小；Th/U值和V/(V+Ni)值分别均小于2和大于0.54,指示水井沱组下段持续缺氧。斜坡相ZK513井Al含量和黏土含量在有机质富集段无明显变化；Ba、Cu、Zn和Ni等营养元素，Mo、U和V等氧化还原敏感元素以及TOC含量的变化趋势耦合，在...     

海洋沉积物中氧化还原敏感元素对水体环境缺氧状况的指示作用

近年来由于人为污染水体富营养化加剧,缺氧区面积不断增大,利用沉积物中氧化还原敏感元素反演水体缺氧情况已经发展成为海洋化学领域的热点研究方向。本文详细阐述了氧化还原敏感元素的富集机制,并总结了利用沉积物中氧化还原敏感元素在不同氧化还原条件下的富集程度反映海水缺氧程度和底质氧化还原状况的一系列指标,如Re/Mo、Cd/U、Th/U、V/Sc、V/(V+Ni)值,U—Mo共变模型,δ~(98/95)Mo,多指标微/痕量元素模型以及氧化还原敏感元素-有机质共变模型等。沉积物中Re、Mo含量、Re/Mo值、自生Mo/U值、Th/U值对上层水体缺氧和氧化条件区分良好,可定量指征上层水体的缺氧情况。沉积物中Re含量近似于1 ng/g(地壳值),Mo含量1μg/g(地壳值),Re/Mo值接近0.3×10~(-3),Mo—U富集系数比为(0.1～0.3)×现代海水,Th/U值2,可指示氧化环境;Re含量在10～30 ng/g,Mo含量近似于1μg/g,Re/Mo值10×10~(-3)～30×10~(-3),Mo—U富集系数比1×现代海水,Th/U值在0～2范围内,可指示缺氧环境;Re含量30 ng/g,Mo富集达到20～40μg/g,Re/Mo值接近0.7×10~(-3)(海水中Re/Mo值),Mo—U富集系数比为(3～10)×现代海水,可指示极度缺氧的硫化环境。Mo_(EF)—U_(EF)交会对数坐标图、氧化还原敏感元素-有机质共变模型指标可定性分析上层水体的缺氧情况;V/(V+Ni)值对于次氧化沉积物指示效果不佳;Cd/U值在次缺氧条件下的变化机制复杂,还需进一步研究。生物扰动、成岩作用、人为污染、水体局限、高有机碳通量、Fe、Mn氧化物循环等因素通过影响氧化还原敏感元素在沉积物中的富集与迁移,从而影响氧化还原敏感元素指标的应用,应剔除有机质吸附与陆源输入等非自生部分的影响,结合各种指标互相印证,综合判别水体氧化还原状态。     

氧化还原敏感微量元素对古海洋沉积环境的指示意义

海洋的氧化还原条件控制着U、V和Mo等氧化还原敏感微量元素在沉积物或沉积岩中的富集程度,所以可以利用沉积物或沉积岩中这些微量元素的含量来重建古海洋的氧化还原状态和沉积环境。海洋沉积物或沉积岩中U、V和Mo的来源少,除了海水提供外,还有陆源碎屑,不过陆源碎屑提供的那部分含量能够被估计。沉积物埋藏之后这些元素（几乎）不发生迁移,保存了沉积时的组成和含量,能较好地反映沉积环境的特征,是古海洋环境的理想指示。在氧化—次氧化的海水环境中U、V和Mo不会富集,缺氧的条件下U和V富集,而在硫化（含溶解的硫化氢）的沉积环境中U、V和Mo在沉积物中都会强烈地富集。利用这种差异,可以根据沉积物或沉积岩中各种微量元素的含量变化来判别沉积时海水的氧化还原状态。但是,必须注意沉积环境的开放与否、成岩作用及重新氧化作用等对微量元素含量的影响。在利用氧化还原敏感元素进行古环境重建时,应首先评估沉积物或沉积岩中特定元素的来源和贡献,剔除非自生部分的影响,然后利用多元素指标综合判别古环境的氧化还原条件,才能获得可靠的结论。     

渝东南地区含锰岩系沉积地球化学特征及成因机制

渝东南“大塘坡式”锰矿形成于Marinoan冰期和Sturtian冰期的间冰期,是在扬子地块东南缘“堑- 垒”式陆缘沉积盆地背景上发育的多阶段、多成因沉积型菱锰矿,成锰期明显受大地构造活动、岩浆作用(火山作用)、“黑烟窗”等热事件影响;且与Rodinia超大陆裂解导致的裂谷盆地成矿作用关系密切。冰期转换、裂谷盆地作用及锰成矿作用三者间的耦合关系明显,并呈现显著相关的沉积地球化学特征。对渝东南不同矿区、不同产状的锰矿及其围岩样品进行的相关Mn/Fe、(Fe+Mn)/Ti、Ba/Sr、U/Th、Y/Ho、SiO2/Al2O3、Al/(Al+Fe+Mn)比值分析和Co/Zn- (Co+Ni+Cu)、La/Yb- ΣREE、La/Yb- Ce/La、lgTh- lgU、La- Ce、lgTh- lgU、(Cu+Ni+Co)×10- Fe- Mn等图解分析,均指示成锰物质的深部来源,成矿受热水影响显著;此外,样品富集As、Sb、Sr、Mo、Ag、Ba、Th、U等热水沉积标识元素。锰矿样品稀土总量平均值为159×10-6,明显高于正常海相沉积阶段形成的菱锰矿稀土总量(19×10-6)。锰矿样品V/(V+Ni)、V/Cr、Ce/La、lgCe/Ce*指示锰矿形成于缺氧环境;Mo、U等氧化- 还原敏感元素富集。成锰盆地的氧化 还原条件制约着锰矿的形成,且成矿过程是沉积、成岩、后生不同阶段矿物相转化的综合结果。锰矿成矿可分为三阶段：第一阶段为沉积期分层性海水上部氧化带MnO2沉淀物富集;第二阶段为沉积期周期性短暂的富氧底流将MnO2沉淀物带入盆地底部沉积;第三阶段为准同生 成岩期,MnO2在缺氧环境中的厌氧细菌或硫酸盐细菌作用下还原为Mn2+,同时产生OH-使底层海水或海底沉积物孔隙流体碱度升高,形成原生菱锰矿及(含)锰碳酸盐沉积物,经成岩作用进一步形成菱锰矿。     

广东三水盆地古近系(土布)心组地球化学特征及其所指示的氧化还原条件

古近系心组红岗段是广东三水盆地的主要生油层,以一套黑—灰黑色页岩沉积为主,其富含有机质、纹层理发育良好的岩层与相对贫有机质、含微体生物化石的微扰动层交替出现。根据纹层状页岩与生物扰动页岩的C-S-Fe关系以及对氧化还原条件敏感的痕量元素(Mo、U、V、Co、Ni、Pb和Cu)地球化学记录,对这两种不同岩相的地球化学特征及其所反映的水体氧化还原条件进行了分析。纹层状页岩的TOC、S含量和DOPT值均较高,TOC-S、TOC-DOPT显示较弱的相关性;而生物扰动页岩的TOC、S含量和DOPT值相对较低,TOC-S、TOC-DOPT相关性显著。痕量元素在两种岩相中的分布也有差别,各元素在纹层状页岩中的丰度均高于生物扰动页岩,尤其是Mo和U具有较高的丰度水平、且在不同岩相中显示明显差别。黑色页岩中的C-S-Fe关系和痕量元素(特别是Mo和U)分布反映了心组红岗段沉积时期湖盆水体的氧化还原条件变化。生物扰动页岩沉积期间,底部水体主要为氧化环境,间歇性出现贫氧条件,硫酸盐还原作用发生于沉积物/水界面及其以下沉积物中。纹层状页岩形成于缺氧的底部水体条件下,水体和沉积物中均可含H2S,为有机质保存以及对氧化还原条件敏感的痕量元素的富集提供了有利条件。     

梅河盆地油页岩特征及成因

梅河盆地为古近纪富含油页岩的小型断陷盆地。岩芯观察、薄片鉴定、有机碳、热解和工业分析等测试分析表明,梅河盆地发育高灰分中含油率型油页岩,油页岩中有机质处于未熟状态;黏土矿物以高岭石和伊利石为主,富含石英等稳定组分,U、Mo等元素较为富集,轻重稀土分异程度高。油页岩突变沉积于煤层之上,且上覆深灰色泥岩,表明其形成于半深湖-深湖环境;Sr/Ba比值和伽马蜡烷含量较低、V/(V+Ni)0.5,表明油页岩形成于缺氧的淡水中。油页岩中有机质来源较为复杂,黑色油页岩有机质丰度含量较高,以高等植物来源为主,油页岩产油率(含油率/TOC)较低;褐色油页岩TOC相对较低,有机质以湖泊生物为主,具有较高的产油率。     

贵州铜仁高地“大塘坡式”锰矿的成矿机制——硫、碳同位素制约

“大塘坡式”锰矿在我国华南黔湘渝地区广泛分布, 是我国最重要的锰矿资源类型之一。它的形成与新元古代Sturtian雪球事件密切相关, 但其具体的成矿机制尚不十分清楚, 还存在许多争论。本文对贵州铜仁地区新近发现的高地超大型锰矿和共伴生黑色页岩中的微量硫酸盐和黄铁矿的硫同位素、菱锰矿等碳酸盐岩及有机碳的碳同位素进行了系统研究, 对该类型锰矿的成矿环境和沉淀机制进行了探讨。高地锰矿大塘坡组一段含锰黑色页岩和锰矿石中硫酸盐的含量很低, 为30.9 ~ 20 439.7 μg/g, 平均3 322.5 μg/g, 硫酸盐的δ34SVCDT为51.5‰~68.1‰, 平均60.4‰。冰碛岩上部铁丝坳组含砾杂砂岩中黄铁矿的δ34SVCDT为26.8‰~59.6‰, 平均52.1‰; 上覆大塘坡组黑色页岩和锰矿石中黄铁矿的δ34SVCDT为53.7‰~65.6‰, 平均63.3‰, 与前人在该区域其它矿区得到的结果一致, 与硫酸盐的δ34SVCDT值差别不大; 黑色页岩和锰矿石全岩的δ34SVCDT为41.4‰~63.9‰, 平均55.7‰。同一样品中, 硫酸盐的δ34S均高于全岩的值, 但差异不大。铁丝坳组顶部含砾杂砂岩的δ13Ccarb为–11.3‰ ~ –8.3‰, 平均–9.6‰, δ13Corg为–31.7‰ ~ –30.1‰, 平均–30.9‰; 大塘坡组一段黑色页岩和锰矿石的δ13Ccarb为–12.4‰ ~ –4.6‰, 平均–8.5‰, δ13Corg为–34.3‰~ –32.6‰, 平均–33.6‰, 二者在含锰段同步下降, 有机碳含量明显升高, 说明有机质对锰矿的形成发挥了重要作用。综上提出, 大塘坡式锰矿形成于滨浅海相半封闭性的断陷盆地之中, 含锰地层中δ34S异常高的黄铁矿是在氧化还原分层明显的静水环境中, 由δ34S异常高的孔隙水硫酸盐在成岩过程中几乎全部还原形成的, 而海水硫酸盐的δ34S正异常与雪球事件、生物爆发和沉积演化等密切相关。雪球融化之后, 在断陷盆地的浅层海水中, 生物活动和光合作用强盛, 氧浓度高, 海水中Mn2+不断被氧化形成氧化锰并从海水中沉淀出来, 而深部还原缺氧富Mn2+的海水不断越过构造脊进来补充。浅层海水中微生物大量繁殖, 死亡后沉降于海底, 导致断陷盆地底部有机质大量聚集, 氧逸度急剧下降。在沉积成岩过程中氧化锰被沉积物中大量有机质全部还原为Mn2+, 有机质本身被氧化为CO2– 3, 二者结合形成菱锰矿。     

高压微波消解法测定醋酸纤维过滤器采集的微尘粒子中的砷镉钴铬铜铁锰镍铅钒锌

最新的流行病学研究表明,空气中较高浓度的悬浮细颗粒可能对人类的健康有不利的影响。根据该项研究显示,由于心脏病、慢性呼吸问题和肺功能指标恶化而导致死亡率的升高与细尘粒子有关。这些研究结果已经促使欧盟于1999年4月出台了限制空气中二氧化硫、二氧化氮、氧化氮、铅和颗粒物含量的法案(1999/30/EC),对各项指标包括对可吸入PM10颗粒的浓度提出了新的限制性指标。PM10颗粒是指可以通过预分级器分离采集的气体动力学直径小于10μm的细颗粒。目前研究的兴趣重点逐步偏向PM2.5这些更细微颗粒物,PM2.5这种颗粒物对健康有明显的不利影响。在欧盟指令2008/50/EC中,对PM10和PM2.5都提     

Shock-induced amorphous textures in plagioclase,Manicouagan, Quebec,Canada

The textural relationships and structural states of optically isotropic labradorite from the Manicouagan, Quebec, impact structure have been examined by light (optical) and transmission electron (TEM) microscopy. Two distinct diaplectic glasses have been recognized based on their contrasting morphology, timing and the inferred modes of formation. The earliest isotropic bands and grain-scale isotropism (maskelynite) optically exhibit a gradational,in situ transformation from crystalline plagioclase with preservation of relict textures (twins, grain boundaries). The same transformation from crystalline to amorphous structure is observed in TEM to occur heterogeneously at scales on the order of the unit cell. The progressive transformation of optical properties reflects an increase in the volume fraction and eventual coalescence of these amorphous units. This maskelynite-type diaplectic glass is interpreted to form in the solid-state directly from crystalline material during the compressional phase of the shock wave. The other isotropic material occurs in spatially discrete tensiongashes and planar deformation features (PDFs) that overprint the maskelynite-type glass. This second type of diaplectic glass (PDF-type) is developed homogeneously within a given glass band and exhibits sharp crystal-glass boundaries, in contrast to the gradational boundaries of the maskelynite-type glass. PDF-type glass is interpreted to form by melting in tensional release zones during passage of the rarefaction wave. These observations emphasize the ability of naturally shocked rocks to preserve subtle evidence of variations in the shock process from highly transient events.     

A catastrophic rockslide-debris flow in Wulong, Chongqing, China in 2009: background, characterization, and causes

On June 5, 2009, a catastrophic rockslide-debris flow occurred at the crest of the Jiweishan Mountain in Wulong, Chongqing, China. Approximately five million cubic meters of limestone blocks slid along a weak interlayer of bituminous and carbonaceous shale. The source mass descended from the upper part of the slope rapidly, crossing a 200-m wide and 50-m deep creek in front of it. Blocked by the opposite steep creek wall, the sliding mass changed its direction and traveled a further 2.2 km along the creek in debris-flow mode, finally forming a large accumulation zone with an average depth of 30 m. This is one of the most catastrophic rockslide events in recent years in China. It buried 12 houses and the entrance of an iron mining tunnel where some 27 miners were working inside. Ten people died, 64 missing, and eight wounded. Immediately after this disaster happened, the government organized an expert team to assist the rescue work. As one of the geological experts, the author did a lot of field investigations and collected first-hand information. Multi-methods including the remote sensing, 3D laser scanning, geophysical exploration, and numerical modeling were used for analyzing the characteristics and the triggering mechanism of the Wulong rockslide. The preliminary investigation results reveal that this rockslide with poor geological conditions was mainly induced by the gravitation and the karst effect and also affected by the previous mining activities. The research in this paper is meaningful and useful for further research on such kind of rockslides that are geologically similar to the Wulong rockslide.     

Wavelength-dispersive X-ray fluorescence spectrometric determination of Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites

Komatiites are mantle-derived ultramafic volcanic rocks. Komatiites have been discovered in several States of India, notably in Karnataka. Studies on the distribution of trace-elements in the komatiites of India are very few. This paper proposes a simple, accurate, precise, rapid, and non-destructive wavelength-dispersive x-ray fluorescence (WDXRF) spectrometric technique for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in komatiites, and discusses the accuracy, precision, limits of detection, x-ray spectral-line interferences, inter-element effects, speed, advantages, and limitations of the technique. The accuracy of the technique is excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Zr, Nb, Ba, Pb, and Th and very good (within 4%) for Y. The precision is also excellent (within 3%) for Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th. The limits of detection are: 1 ppm for Sc and V; 2 ppm for Cr, Co, and Ni; 3 ppm for Cu, Zn, Rb, and Sr; 4 ppm for Y and Zr; 6 ppm for Nb; 10 ppm for Ba; 13 ppm for Pb; and 14 ppm for Th. The time taken for determining Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba, Pb, and Th in a batch of 24 samples of komatiites, for a replication of four analyses per sample, by one operator, using a manual WDXRF spectrometer, is only 60 hours.     

Analysis of F, Al, Mn, Zn, Fe, Cu, Ca and Mg concentrations in brick teas from main producing areas in China

Brick-tea-type fluorosis is a peculiar endemic disease in China, which had been discovered in minority areas of western China since 1980, and distributed mainly in Tibet, Inner Mongolia, Gansu, Xinjiang, Qinghai and parts of Sichuan Province. The prevalence rate of fluorosis in Tibetan and Mongolian nationality people was higher. Epidemiological investigation showed that fluorosis morbidity and degrees were different in different brick-tea drinking areas, and it was probably caused by drinking various kinds of brick tea from different regions. Therefore, we collected 33 samples of brick tea from six provinces where minority nationalities were accustomed to drinking a large quantity of brick tea. F concentrations were determined by the combustion hydrolysis-ion selective electrode method. The results showed that among the brick teas, the F concentrations ranged from the minimum 74.1 mg/kg in Yunnan Province to the maximum 991.2 mg/kg in Sichuan Province. Besides, there was a great difference among the various kinds of brick tea, and F concentrations decreased in the order of Kang brick tea, Green brick tea, Black brick tea, Mi brick tea, Fu brick tea, Chitsu ping tea, Puerh tea, and Tuo tea. The average F concentration in brick teas was 431.92 mg/kg.     

湖北宜昌王家湾五峰组顶部Chondrites的发现及其环境意义

本文报道了湖北宜昌王家湾剖面五峰组笔石页岩段观音桥层发现的遗迹化石Chondrites的分布及其生态特点。结合生物相和同期上扬子海盆相对海平面的变化,分析了盆地水体底域在缺氧一富氧转折时期的古氧相变化特征：指出五峰组笔石页岩段上部地层沉积底域为典型的缺氧环境,在其与上覆观音桥段之间的沉积转换面附近发生了从无氧到有氧的转变,观音桥段中Hirnantia动物群繁盛于富氧的海底环境。     

Neutron-capture elements in halo, thick-disk, and thin-disk stars. Strontium, yttrium, zirconium, cerium

We derived Sr, Y, Zr, and Ce abundances for a sample of 74 cool dwarfs and subgiants with iron abundances, [Fe/H], between 0.25 and ?2.43. These estimates were obtained using synthetic spectra, assuming local thermodynamic equilibrium (LTE) for Y, Zr, and Ce, allowing for non-LTE conditions for Sr. We used high-resolution (λ/Δλ?40 000 and 60 000) spectra with signal-to-noise ratios between 50 and 200. We find that the Zr/Y, Sr/Y, and Sr/Zr ratios for the halo stars are the same in a wide metallicity range (?2.43 ≤ [Fe/H] ≤ ?0.90), within the errors, indicating a common origin for these elements at the epoch of halo formation. The Zr/Y ratios for thick-disk stars quickly decrease with increasing Ba abundance, indicating a lower rate of production of Zr compared to Y during active thick-disk formation. The thick-disk and halo stars display an increase in the [Zr/Ba] ratio with decreasing Ba abundance and a correlation of the Zr and Eu overabundances relative to Ba. The evolutionary behavior of the abundance ratios found for the thick-disk and halo stars does not agree with current models for the Galaxy’s chemical evolution. The abundance ratios of Y and Zr to Fe and Ba for thin-disk stars, as well as the abundance ratios within each group, are, on average, solar, though we note a slight decrease of Zr/Ba and Zr/Y with increasing Ba abundance. These results provide evidence for a dominance of asymptotic-giant-branch stars in the enrichment of the interstellar medium in heavy elements during the thin-disk epoch, in agreement with the predictions of the nucleosynthesis theory for the main s-process component.     

Flood anticipation,reality, and uncertainty,the 2019 flood in Khuzestan,Iran

Natural Hazards - Despite the application of various methods to calculate uncertainty in flood vulnerability assessments, the challenge of uncertainty remains. The main purpose of this study was to...     

Arsenic in streams,stream sediments,and ground water,fairbanks area,alaska

Arsenic concentrations of less than 5 ppb to as large as 1,260 ppb in stream waters and from 5 ppm to 4,000 ppm in stream sediments were found in the Pedro Dome-Cleary Summit area, Alaska. Waters from three of 20 wells sampled had arsenic concentrations exceeding the U.S. Public Health Service recommended limit of 50 ppb. The high arsenic levels are a consequence of arsenic enrichment in the rocks of the area. Placer and lode-gold mining may increase the arsenic content of the waters by exposing arsenic-containing rocks to surface waters and by increasing the load of arsenic-rich sediments in the streams. Finding these disturbingly large concentrations of arsenic in the waters of the Fairbanks area was the major result of this work, inasmuch as a subsequent study (to be published) revealed arsenic concentrations as large as 10 ppm in domestic wells and prompted an extensive study by Federal and State agencies of the health hazard posed by these arsenic-rich waters.     

Disruption in Biogeosciences:Conceptual,Methodological,Digital,and Technological

正Over four years ago,a group of investigators came together to determine if Big Data approaches (specifically data mining,machine learning and analytics in general) might provide insight into some of the grand challenges in Earth's history:evolution of minerals,rise of oxygen,life,influence of super continental cycles,quantifying the magnitude of extinction events,and more.As a result,the team of mineralogists,petrologists,geochemists,