Adsorbed silica in stalagmite carbonate and its relationship to past rainfall

Despite considerable work on other trace elements, the incorporation of dissolved silicon from cave waters into speleothems has not been previously investigated. In this study, the controls on dissolved Si in cave waters and on adsorbed Si in resulting speleothems are therefore investigated. Bedrock (dolomite), soil water, dripping water, and cave carbonates were retrieved from Heshang Cave situated in the central Yangtze valley of China and were subjected to analysis of dissolved Si content (plus accompanying Ca and Fe analyses). Soil waters have Si/Ca of 45.5 mmol/mol, compared to only 3.2 mmol/mol in the dolomite bedrock, demonstrating that >80% of the dissolved Si must come from dissolution of silicate minerals in the soil. Drip waters have a dissolved Si concentration of ≈4.2 μg/mL, similar to that in the overlying soil water. Actively growing cave carbonates have a Si/Ca of 0.075 mmol/mol suggesting a partition coefficient for incorporation of dissolved silicon of 0.0014, in good agreement with previous laboratory studies. Extrapolating the results of these laboratory studies to the cave environment suggests that changes in Si/Ca in cave carbonates are likely to be primarily controlled by changes in drip-water Si/Ca. The drip-water Si/Ca will, in turn, be controlled by the rate of wind-blown silicate supply; by soil weathering rates; by rainfall dilution; and by precipitation of calcite. The general expectation is that these effects combine to produce high Si/Ca in speleothems during times of low rainfall. A δ¹⁸O record from a Heshang Cave stalagmite which grew between 20 and 11 thousand years ago allows these controls to be tested. Correlation of high Si/Ca with high δ¹⁸O demonstrates that regional rainfall exerts significant (but not complete) control on speleothem Si/Ca. With further understanding, speleothem Si/Ca may provide a proxy for past rainfall to complement existing proxies such as δ¹⁸O and Mg/Ca.     

山西陵川地区上石炭统-下二叠统太原组15#煤层成煤环境分析

山西陵川地区上石炭统一下二叠统太原组K1段出露良好,其顶部的15#煤层为沁水盆地石炭二叠系煤田主采煤层之一.通过对K1段岩性、沉积构造、沉积序列、植物化石及煤岩组分等特征的综合分析,将该段划分为潟湖、障壁岛、潮坪、溢流扇等4种沉积相以及混合坪、泥坪、泥炭坪等3种沉积亚相.结合15#煤层沉积背景及煤岩特征,认为本区15#煤层是在海退导致潮坪暴露形成古土壤之后所产生的低位泥炭沼泽的基础上形成的,它结束于之后的一次快速的、更大规模的海侵.在综合研究成煤地质背景的基础上,提出研究区15#煤层属于滨岸潮坪成煤模式.这一成果为今后山西沁水盆地东南部该煤层的深层勘探开发及煤层气的生成地质背景提供了基础理论资料.     

华熊地块中生代岩浆作用的物质继承性

中生代是华熊地块最重要的岩浆作用时期。通过对其中主要地体中燕山期改造型花岗岩和同熔型花岗岩的同位素研究,结合其形成物质背景和地质特征,认为它们的物质特征主要取决于它们继承各自不同的地体物质(特别是基底物质)和同一地体物质的多少程度。地体及其中生代岩浆作用的构造环境是解释这一继承机理的主要因素。     

水库群优化调度函数的人工神经网络方法研究

提出了研究水库群优化调度函数的人工神经网络方法,并探讨了神经网络的训练参数、训练方法和训练样本的改变对网络训练和应用效果的影响。实例研究表明,模型及其算法是可行的、有效的。     

内蒙古阿巴嘎旗乌和尔楚鲁图钼矿区成矿斑岩的岩石地球化学特征与年代学

乌和尔楚鲁图钼矿床位于国内重要的二连东乌旗钼矿成矿带中,为近几年新发现的斑岩型钼矿床.本次就该矿床成矿岩体的地球化学及其U-Pb年代学开展相关研究.结果表明: 矿区中的成矿岩体属过铝质、高钾钙碱性系列;富集大离子亲石元素(LILE)、亏损高场强元素(HFSE),具有与南岭型花岗岩相似的地球化学特征.锆石LA-ICP-MS U-Pb定年显示,与乌和尔楚鲁图钼矿床成矿有关的花岗斑岩形成于中侏罗世((160 ± 1)Ma).因此,可推测乌和尔楚鲁图钼矿床斑岩型钼矿的成矿时代为燕山早期.综合研究认为乌和尔楚鲁图斑岩型钼矿床形成于后碰撞的构造环境.     

Results for Rarely Determined Elements in MPI-DING, USGS and NIST SRM Glasses Using Laser Ablation ICP-MS

New analytical results are reported for rarely determined elements Be, B, Ge, As, Mo, Rh, Pd, Ag, Cd, In, Sn, Sb, W, Re, Ir, Pt, Au, Tl and Bi in MPI‐DING and USGS (BCR‐2G, BHVO‐2G, BIR‐1G) silicate glasses and the NIST SRM 610‐614 synthetic soda‐lime glasses using 193 nm ArF excimer laser ablation and quadrupole ICP‐MS. The method used involved external calibration against GOR132‐G for Ir and NIST SRM 610 for other elements, internal standardisation using Ca, and ablation with a crater diameter of 160 μm and a pulsed laser repetition rate of 10 Hz. Small amounts of nitrogen (5 ml min^?1) were added to the central channel gas of the plasma to improve the limits of detection for most of these elements by a factor of 1.2–2.5 and to reduce the oxide interference level to 0.02% (ThO⁺/Th⁺). Under these conditions, the LODs for most of these rarely determined elements were within the range 0.1 to 10 ng g^?1. The operating conditions that were required to minimise ICP‐induced fractionation (U⁺/Th⁺≈ 1) in the mode without nitrogen were accompanied by a 50–60% reduction in sensitivity for elements such as Ca, Au and Pt. In contrast, ICP‐induced fractionation could be minimised (U⁺/Th⁺≈ 1) with no loss of analyte sensitivity in the nitrogen mode. Interferences of CuAr⁺, ZnAr⁺, Cd⁺, Pb²⁺ and Sn⁺ on Pd⁺, Rh⁺, Cd⁺ and In⁺ were corrected. Oxide interferences were not considered due to their lower production rate. Analytical precision, as given by one relative standard deviation (% RSD) was less than 15% for most of the elements present at concentrations greater than 0.1 μg g^?1. A significant negative correlation was found between logarithmic concentration and logarithmic RSD, with a correlation coefficient of ?0.76. This trend indicates that possible chemical heterogeneities for most of these elements are smaller than the analytical uncertainty. Our results for Be, B, Ge, Sb and W are generally in good agreement with their reference values. In contrast, other elements in many of the reference glasses have only information values, upper limits or even no values, which restrict any detailed evaluation of the accuracy of the determined values. However, concentrations from multiple isotopes of one element analysed in this study showed excellent agreement, which guarantee the quality of our data to a certain extent.     

RCCC-WBM水量平衡模型在北方典型流域的适用性研究

流域水文模型是开展环境变化影响分析和水资源评价的重要工具。以山西省的5个不同尺度的代表性流域为研究对象,分析了RCCC-WBM模型在山西省的区域适用性。结果表明:RCCC-WBM模型能够较好地模拟出山西省径流年内分配特征和年代际变化特点,对典型流域月径流量模拟的Nash-Sutcliffe模型效率系数超过65%,水量模拟误差也较小,该模型在山西省具有较好的适用性,可以用于山西省水资源评价等方面的科学研究。     

Trace Elements in Fluid Inclusions in the Carlin—Type Gold Deposits,Southwestern Guizhou Province

Fluid inclusions in quartz from the Lannigou and Yata Carlin-type gold deposits in southwestern Guizhou were analyzed by inductively coupled plasma-mass spectrometry for their trace elements(Co,Ni,Cu,Pb,Zn,Pt,etc.).The results show that quartz fluid inclusions entrapped at different ore-forming stages contain higher Co,Ni,Cu,Pb and Zn.It has been found for the first time that the ore-forming fluids responsible for the Carlin-type gold deposits are rich in Pt.From this it can be concluded that basic volcanic rocks seem to be one of the important sources of ore-forming materials for the Carlin-type gold deposits.     

山东招远大尹格庄金矿成矿流体特征

大尹格庄金矿位于中国胶北地体西北部招平断裂带下盘的蚀变花岗质碎裂岩 (绢英岩 )带中 ,断裂上盘为胶东群变质岩系。金主要产于黄铁绢英岩和黄铁矿±多金属硫化物 石英±碳酸盐脉 -细网脉中 ,构成细脉 -浸染状矿石。对蚀变围岩和金矿石中流体包裹体的研究表明钾长石化岩 (钾长石 -石英脉 )和绢英岩 (第 I和第 II阶段 )的石英中含有丰富的 CO2 -H2 O包裹体 ,而金 -硫化物矿石和石英 -碳酸盐脉 (第 III和第 IV阶段 )中 CO2 - H2 O包裹体数量逐渐减少。显微测温指示 ,钾长石化岩和绢英岩石英中的 CO2 - H2 O包裹体的均一温度范围为 2 80～ 36 0℃ ;而金 -黄铜矿和金 -方铅矿 -闪锌矿矿石中包裹体的均一温度分别为 2 40～ 2 75℃和 180～ 2 5 0℃。显微测温和激光拉曼探针分析表明 ,第 I和第 II阶段的成矿流体含 10～ 2 5mol% CO2 ;而第 III和第 IV阶段的含 <5～ 10 mol% CO2 ,并含少量至可观数量 CH4,H2 S和 SO2 等。广泛的黄铁矿化、碳酸盐化蚀变以及缺乏较高盐度的水包裹体说明金很可能是以硫络合物和碳络合物形式被搬运。金的沉淀与温度下降、由裂隙的(重复 )开放引起明显的压力降低和原始流体的不混溶作用有关 ,具多阶段成矿特点     

Successional stages of biological soil crusts and their microstructure variability in Shapotou region (China)

In order to investigate succession of biological soil crusts (BSCs) and their microstructure variability, we conducted this work in Shapotou revegetation region at the southeast edge of Tengger Deser. The results showed that BSCs generally succeeded as a pathway of “Algae crusts, algae–lichen crusts, lichen crusts, lichen–moss crusts and moss crusts”. Occasionally mosses directly occurred on algae crusts, and BSCs succeeded from algae crusts to moss crusts. Crust vertical stratification was a common phenomenon, from top to bottom an inorganic layer, algae-dense layer and algae-sparse layer were divided in algae crusts; a thallus layer, rhizoid layer and sub-rhizoid layer in lichen crusts; a “stem-leaf” layer, rhizoid layer and sub-rhizoid layer in moss crusts, respectively. The main crust binding organisms varied from filamental cyanobacteria (dominated by Microcoleus) in algae crusts to lichen rhizoids, free-living cyanobacterial filaments and fungal hyphaes in lichen crusts, and to moss rhizoids and fungal hyphaes in moss crusts. The dominant phototrophic organisms varied from Microcoleus (algae) in algae crusts to Collema (lichens) in lichen crusts, and to Bryum (or Didymodon and Tortula; mosses) in moss crusts. Total phototrophic biomass increased while the free-living algal biomass decreased with the succession of BSCs. In addition, exopolysaccharides and fine particles accumulated in the course of development and succession of BSCs, all of which lead to a gradual increase in crust thickness and porosity, while decrease in the bulk density.