Evidence for high‐temperature fractionation of lithium isotopes during differentiation of the Moon          下载免费PDF全文

James M. D. Day  Lin Qiu  Richard D. Ash  William F. McDonough  Fang‐Zhen Teng  Roberta L. Rudnick  Lawrence A. Taylor 《Meteoritics & planetary science》2016,51(6):1046-1062

Lithium isotope and abundance data are reported for Apollo 15 and 17 mare basalts and the LaPaz low‐Ti mare basalt meteorites, along with lithium isotope data for carbonaceous, ordinary, and enstatite chondrites, and chondrules from the Allende CV3 meteorite. Apollo 15 low‐Ti mare basalts have lower Li contents and lower δ⁷Li (3.8 ± 1.2‰; all uncertainties are 2 standard deviations) than Apollo 17 high‐Ti mare basalts (δ⁷Li = 5.2 ± 1.2‰), with evolved LaPaz mare basalts having high Li contents, but similar low δ⁷Li (3.7 ± 0.5‰) to Apollo 15 mare basalts. In low‐Ti mare basalt 15555, the highest concentrations of Li occur in late‐stage tridymite (>20 ppm) and plagioclase (11 ± 3 ppm), with olivine (6.1 ± 3.8 ppm), pyroxene (4.2 ± 1.6 ppm), and ilmenite (0.8 ± 0.7 ppm) having lower Li concentrations. Values of δ⁷Li in low‐ and high‐Ti mare basalt sources broadly correlate negatively with ¹⁸O/¹⁶O and positively with ⁵⁶Fe/⁵⁴Fe (low‐Ti: δ⁷Li ≤4‰; δ⁵⁶Fe ≤0.04‰; δ¹⁸O ≥5.7‰; high‐Ti: δ⁷Li >6‰; δ⁵⁶Fe >0.18‰; δ¹⁸O <5.4‰). Lithium does not appear to have acted as a volatile element during planetary formation, with subequal Li contents in mare basalts compared with terrestrial, martian, or vestan basaltic rocks. Observed Li isotopic fractionations in mare basalts can potentially be explained through large‐degree, high‐temperature igneous differentiation of their source regions. Progressive magma ocean crystallization led to enrichment in Li and δ⁷Li in late‐stage liquids, probably as a consequence of preferential retention of ⁷Li and Li in the melt relative to crystallizing solids. Lithium isotopic fractionation has not been observed during extensive differentiation in terrestrial magmatic systems and may only be recognizable during extensive planetary magmatic differentiation under volatile‐poor conditions, as expected for the lunar magma ocean. Our new analyses of chondrites show that they have δ⁷Li ranging between ?2.5‰ and 4‰. The higher δ⁷Li in planetary basalts than in the compilation of chondrites (2.1 ± 1.3‰) demonstrates that differentiated planetary basalts are, on average, isotopically heavier than most chondrites.  相似文献   

A geochemical survey of trace elements in agricultural and non-agricultural topsoil in Dexing area,China   总被引：2，自引：0，他引：2  

Yanguo Teng  Shijun Ni  Jinsheng Wang  Rui Zuo  Jie Yang 《Journal of Geochemical Exploration》2010

In China, soil pollution is very serious, which has jeopardized the ecology, food safety, the people's health, and even the sustainable development of agriculture. In order to investigate the soil pollution situation, a total of 874 agricultural and non-agricultural topsoil samples were collected from Dexing area, northeast of Jiangxi Province, China. The total elemental concentrations of 17 elements (As, Hg, Mo, Cd, Cr, Zn, Cu, Mn, Ti, Pb, Fe, Ca, K, Si, Al, Mg, and Na) were determined. The geochemical background and threshold was predicted with the method of the median ± median absolute deviation (MAD). The agricultural soil median concentration of trace elements was similar to that of the non-agricultural soil. In contrast to Jiangxi soil background of trace elements, the geochemical background of the study area was obviously higher. The maps of the pollution indices for As, Cd, Cr, Cu, Hg, Mn, Mo, Pb, Ti and Zn of non-agricultural soil and agricultural soils in the study area, showed that the highest level of pollution is distributed near and along the Lean River, especially in the neighboring and surrounding Dexing and Leping mining area.  相似文献   

Microbial community changes in the digestive tract of the clam Meretrix petechialis in response to Vibrio parahaemolyticus challenge     

Wang  Hongxia  Yue  Xin  Yu  Jiajia  Wang  Rui  Teng  Shuangshuang  Fang  Jun  Liu  Baozhong 《中国海洋湖沼学报》2021,39(1):329-339

Journal of Oceanology and Limnology - Disease in clams frequently occurred over the last decade and has become a serious threat to the clam aquaculture industry and natural stocks. Mass clam...  相似文献   

大巴山国家地质公园构造地貌景观构造变形期次研究   总被引：1，自引：0，他引：1  

付顺  阚瑷珂  肖进  胡瑾  向芳  张腾  李文韬 《地球学报》2014,35(4):510-518

通过野外路线考察,典型地区填图,地质、地形图判读发现,大巴山国家地质公园主要构造地貌景观横向分布呈现由NE至SW即从造山带向前陆盆地方向逐渐减弱特征;纵向上明显受早期构造格局和岩石类型约束,在区域上呈现NW—SE向延展的平行岭谷地貌,山峰和谷地的走向与地质构造线基本一致。通过对主要构造地貌景观构造应力和变形期次判别探讨,确定构造地貌景观形成的构造期次大致为三期,应力主要来自于NE—SW、SE—NW向,反映该区不仅受到NE—SW向的冲断挤压变形作用,还受到SE—NW向的右旋剪切挤压变形作用,推测是由多期受力叠加改造而成。通过ESR及14C定年确定距今12 Ma以来,该区在500 kaBP、278 kaBP、29 kaBP分别出现三次规模较大的快速抬升运动,提供了与其构造景观形成密切相关的新构造运动年代学证据。  相似文献   

陕北煤矿区地质环境保护与恢复治理措施——以神府矿区郭家湾煤矿为例     

李永红  何意平  康金栓  张新宇  李辉  滕宏泉  丁佳 《中国煤炭地质》2014,(4):41-45,57

郭家湾煤矿地处神府矿区新民采区西北部,为生态环境脆弱区。井田七层煤三个煤组开采后引发地面塌陷、含水层疏干、土地结构变化等地质环境问题,严重制约了地方经济的发展。为了煤炭资源可持续发展,研究陕北煤矿区地质环境保护与恢复治理措施,以1∶10000野外详细调查为依据,首先进行现状评估,然后针对矿山工程建设可能遭受、加剧、引发的矿山地质环境问题进行预测评估,最后提出了以移民搬迁、回填裂缝、生态恢复、建立矿山地质环境监测体系等为主的防治措施,让煤矿开采与矿山地质环境问题恢复治理并行。旨为陕北地区乃至全国煤矿,在保护地质环境中开发利用矿产资源提供依据和示范。  相似文献   

Suitability evaluation of rural residential areas under the threat of geological disasters:A case study in Yinchanggou watershed of Pengzhou City     

LIU Teng  REN Guangming  WANG Meng  YU Tianbin 《中国地质调查》2014,7(2):95-100

At present, the research on the layout of rural residential areas in the mountainous environment under the threat of earthquake disasters and frequent geological disasters is still rare. Taking Yinchanggou watershed in Longmenshan Town of Pengzhou City as an example, based on the summary of the geological hazard development characteristics in this area, the authors carried out the hazard risk zoning through 8 indexes. Then the geological hazard risk zoning was used as the primary factor to evaluate the suitability of rural residential areas. Besides, combined with the topographical conditions, socio-economic situation and ecological environment, a suitable evaluation index system for rural residential land under the threat of geological disasters was constructed, with the restrictive conditions of extremely high-risk areas, single geological hazards, slopes ≥25° and basic farmland protection areas. Finally, the fuzzy comprehensive evaluation method was used to evaluate the suitability of residential land in Yinchanggou watershed of Pengzhou City. The results show that high suitability areas account for 4.2% of the total area of the study area, moderate suitability areas 11.4%, low suitability areas 10.5%, and unsuitable areas 73.8%. The “suitable” areas for rural residential land are mainly distributed along the highway, and some are multiple “blocky” concentrated distribution areas. The terrain is flat and the traffic condition is convenient, which can provide some guidance for the selection of new rural residential locations.  相似文献   

青藏高原古人类的艺术创作——基于中更新世手脚印形态分析     

章典  王蕾彬  MatthewR Bennett  张盛达  张海伟  李腾  张悦  苏佳佳  王晓晴 《地理科学》2022,42(5):782-790

在第二次青藏科考过程中,作者在西藏自治区拉萨市邱桑村的古泉华沉积上新发现了由5个手印和5个脚印组成 “岩面艺术” （parietal art）。对这一“岩面艺术”进行解剖学测量、3D 模型模拟、铀系测年和手脚印形态分析后,得到以下认识：① “岩面艺术”是在泉华没有成岩之前由古人类有意压上去的;② “岩面艺术”所在岩层的U/Th年代为226~169 ka B.P.,这其中包含一个手指印岩层的表面直接年龄（207~188 ka B.P.）;③ 这一发现是迄今为止发表的古人类在青藏高原上活动的最早记录之一,也为古人类适应高寒、低氧环境提供了新的证据;④ 此岩面艺术是目前世界上已知的最古老的艺术,上面的手印也是古人类留下的最早的手印;⑤ 这一原始的岩面艺术表明,创作它的古老人种可能具有一定的认知和空间感知能力,此岩面艺术的发现也将有可能改写人类艺术史,并且加深我们对已消失的古人类认知水平的认识。  相似文献   

钒矿床研究进展与展望          下载免费PDF全文

杨立飞  李增华  欧阳永棚  邓腾  邓友国  孟德磊  郑华 《沉积与特提斯地质》2023,43(1):48-58

钒是工业国家重点关注和争夺的资源,已被部分国家列为关键金属。本文对矿床类型、地质特征、时空分布以及成矿机制等方面进行了系统总结和分析,以期丰富钒成矿理论研究,为提高钒资源的预测和勘查效率提供支撑,为钒资源储备提供保障。研究发现,钒矿床主要分为岩浆型和沉积型,其中岩浆型钒矿床（主要指钒钛磁铁矿床）成矿与铁镁质–超铁镁质岩及部分斜长岩侵位密切相关,成矿年龄与成岩年龄一致,钒可能来自上地幔并在岩浆演化过程中结晶析出赋存于含钒钛磁铁矿中;沉积型钒矿床多形成于黑色岩系及部分砂岩中,成矿多集中于上寒武世,钒可能来自海水和赋矿围岩,由于氧化还原电位降低,以吸附和类质同象等形式赋存于有机质和硅酸盐矿物中。同时,钒矿床的成因研究存在较多问题,如成矿物质钒的来源、迁移过程、赋存形式及富集条件等。笔者建议在今后研究中通过分析钒化学行为、围岩沉积物理–化学–生物条件及岩浆演化的地质动力背景来解析钒矿床成因机制。  相似文献   

基于机器学习模型的淮河流域中长期径流预报研究     

胡义明  陈腾  罗序义  唐超  梁忠民 《地学前缘》2022,29(3):284-291

准确可靠的中长期径流预报是支撑水资源科学调配、提高水资源利用效率的关键。本研究采用AdaBoost模型(AdB)、随机森林模型(RF)和支持向量机模型(SVM)进行淮河流域王家坝和蚌埠站当年11月至次年10月共12个月的中长期径流预报研究。采用置换准确度重要性度量法从130项气象-气候因子及前期降雨/流量构建的1 562个因子变量中筛选出影响各月径流的关键因子,构建了基于AdB、RF和SVM模型的各月径流预报模型,模型参数采用随机搜索技术并结合交叉验证方式确定。采用变幅误差合格率和等级(五级)预报合格率指标对模型的预报精度进行了评估。变幅误差合格率指标表明,王家坝12个月的平均合格率分别为99.8%(AdB)、96.6%(RF)和95.9%(SVM),蚌埠站分别为100%(AdB)、94.8%(RF)和93.8%(SVM);等级预报合格率指标表明,王家坝12个月的平均合格率分别为79.0%(AdB)、76.4%(RF)和79.9%(SVM),蚌埠站分别为81.0%(AdB)、75.6%(RF)和76.6%(SVM)。模型均具有较好的预报效果,但RF和SVM模型对于高流量值的预报存在偏低现象,AdB模型整体上优于RF和SVM模型。  相似文献   

基于窗口理论的时频分析方法研究     

贺梅  刘财  周寅  罗腾  张鹏  丁玲 《世界地质》2015,34(2):476-483

通过对比短时Fourier变换、连续小波变换、S变换、广义S变换等时频分析方法发现,从窗的维度看,它们具有统一的内积形式,差别在于窗函数中σ(f)的取值。通过分析相应方法中σ(f)随信号频率的变化规律,以及随之产生的时窗与时频分辨率问题,解释广义S变换的相对优越性。将广义S变换应用于四类薄互层模型,研究薄互层时频特性与地质特性的对应关系,指导地层旋回方向的预测。  相似文献