A numerical study of the dynamics of the wave-driven circulation within a fringing reef system

The circulation driven by wave breaking, tides and winds within a fringing coral reef system (Ningaloo Reef) in Western Australia was investigated using the ocean circulation model ROMS two-way coupled to the wave model SWAN. Currents within the system were dominantly forced by wave breaking, with flow driven over the shallow reefs and towards the lagoon, which returned to the ocean through channels in the reef. Hindcast model simulations were compared against an extensive field dataset, revealing that the coupled wave–circulation model could accurately predict the waves and currents throughout this morphologically complex reef–lagoon system. A detailed momentum budget analysis showed that, over the reef, a dominant cross-shore balance was established between radiation stress gradients and a pressure (mean water level) gradient (similar to a beach). Within the lagoon, alongshore currents were primarily balanced by alongshore gradients in wave setup, which drove flow towards (and ultimately out) the channels. The importance of these wave-driven currents to Ningaloo Reef was quantified over a full seasonal cycle, during periods when wave and wind conditions significantly differed. These results showed that wave breaking still overwhelmingly dominated the circulation and flushing of Ningaloo Reef throughout the year, with winds playing an insignificant role.     

First-principles Study on Equilibrium Sn Isotope Fractionations in Hydrothermal Fluids

Tin (Sn) isotope geochemistry has great potential in tracing geological processes. However, lack of equilibrium Sn isotope fractionation factors of various Sn species limits the development of Sn isotope geochemistry. Equilibrium Sn isotope fractionation factors (124Sn/116Sn and 122Sn/116Sn) among various Sn(II, IV) complexes in aqueous solution were calculated using first-principles calculations. The results show that the oxidation states and the change of Sn(II, IV) species in hydrothermal fluids are the main factors leading to tin isotope fractionation in hydrothermal systems. For the Sn(IV) complexes, Sn isotope fractionation factors depend on the number of H2O molecules. For the Sn(II) complexes, the Sn isotope fractionation between Sn(II)?F, Sn(II)?Cl and Sn(II)?OH complexes is mainly affected by the bond length and the coordination number of anion, whereas the difference in 1000lnβ values of Sn(II)?SO4 and Sn(II)?CO3 complexes is insignificant with the change of anion coordination number. By comparing the 1000lnβ values of all Sn(II, IV) complexes, the enrichment trend in heavy Sn isotopes is Sn(IV) complexes > Sn(II) complexes. The equilibrium Sn isotopic fractionation factors enhance our understanding of the tin transportation and enrichment processes in hydrothermal systems.     

2020年夏季我国气候异常特征及成因分析

2020年夏季我国天气气候极为异常,全国平均降水量为373.0 mm,较常年同期偏多14.7%,为1961年以来次多;季节内阶段性特征显著,6—7月多雨带主要位于江南大部—江淮地区,8月则主要在东北、华北及西南地区,致使2020年夏季雨型分布异常,不是传统认识上的四类雨型分布。通过对同期大气环流和热带海温等异常特征分析发现,6—7月,欧亚中高纬环流表现为"两脊一槽"型,东亚副热带夏季风异常偏弱,西太平洋副热带高压(以下简称西太副高)较常年同期显著偏强、偏西,第一次季节性北跳偏早,第二次北跳明显偏晚,且表现出明显的准双周振荡特征;使得来自西北太平洋的转向水汽输送偏强,并与中高纬不断南下的冷空气活动相配合,水汽通量异常辐合区主要位于长江中下游地区,导致江淮梅雨异常偏多。热带印度洋持续偏暖对维持6—7月西太副高偏强偏西及东亚夏季风异常偏弱起到了重要作用。8月,欧亚中高纬环流调整为"两槽一脊"型,蒙古低压活跃;西太副高也由前期偏纬向型的带状分布转为"块状"分布,脊线位置偏北;沿西太副高外围的异常西南风水汽输送延伸至华北一东北南部,形成自西南到东北的异常多雨带,与6—7月江淮流域降水异常偏多的空...     

利用吸收和发光光谱技术分析高温高压天然富氢钻石的鉴定特征

对不同类型褐色钻石进行高温高压处理和结构特性研究是钻石研究中的难点和重点之一。前人对富氢钻石的研究主要集中于其特殊的生长结构以及其形成环境的探讨,而对富氢钻石经高温高压处理后的变化特征鲜有涉及。本文对经高温高压处理前后的富氢钻石的红外光谱、紫外可见吸收光谱以及光致发光光谱等谱学特征进行了对比,研究其鉴定特征。结果表明:高温高压处理前后的富氢钻石的光谱特征具有明显差异,特别是红外光谱,经处理后的钻石中与氮氢有关的吸收峰如3310 cm~(-1)、3232 cm~(-1)、3189 cm~(-1)等明显减弱甚至消失,并出现与孤氮有关的新的2688 cm~(-1)吸收峰;紫外可见光吸收光谱中,经处理的褐色钻石中的无选择性吸收(钻石呈褐色的原因)变为孤氮的典型吸收,即550 nm至短波的吸收以及N_3中心(415 nm)的吸收均明显增强,因此钻石也由原来的褐色变为黄色。钻石经处理前后的光致发光光谱中,与氮原子有关的缺陷类型、峰的强度以及缺陷组合也有变化。本文获得的光谱变化特征,为准确鉴定高温高压处理的黄色富氢钻石提供了依据,也为解释与氢和氮相关的晶格缺陷在高温条件下的变化机理提供了理论基础。     

Hydromorphic dispersion of Cu and Mo over mineralized granodiorite in a high rainfall peaty area in Ireland: geochemical interpretation and case study

Dispersion of Cu and Mo in mainly ombrotrophic-type peat and till on mineralized Galway Granodiorite, Ireland, is controlled by high rainfall (leaching of surface peat), organic content of till, limonite/bog iron, Eh and pH. Sampling surface blanket peat should be avoided in mineral exploration due to downward leaching. Copper accumulates more effectively than Mo in slightly reduced basal peat, organic-rich till, and organic-rich drain and stream beds. Molybdenum, being more mobile, occurs in a much broader range of organic-rich till, and limonite-stained till and lakeshore sediments. Hence, Mo is a useful pathfinder for Cu. Mobility of Cu and Mo is low due to complexation and/or adsorption, hence overburden anomalies make reasonable drill targets.     

好氧强化降解湖底有机碎屑的初步研究

以巢湖湖底有机碎屑为研究对象,基于对有机碎屑中总有机碳的测定,研究了利用好氧强化降解湖底有机碎屑.研究了有机碎屑的可生化性及好氧强化降解湖底有机碎屑的效果,并讨论了有机碎屑的浓度及曝气量对其降解效果的影响.结果说明,处理的有机碎屑具有较好的可生化性,在反应30 h左右,降解达到了平衡,总去除率达到了50.69%,降解速率常数K₂₅为0.19 h^-1.有机碎屑的浓度以及曝气量对降解效果具有一定的影响.强化好氧法与传统的对底泥处理的方法相比具有更快、更好的效果,为预防及治理水体黑臭现象提供了新的途径.     

Petrogenetic and geodynamic origin of the Neoarchean Doré Lake Complex,Abitibi subprovince,Superior Province,Canada

International Journal of Earth Sciences - The Neoarchean (ca. 2728 Ma) anorthosite-bearing Doré Lake Complex in the northeastern Abitibi subprovince, Quebec, was emplaced into an...     

盐度对冠瘤海鞘幼体附着与变态的影响

通过盐度梯度实验检验了盐度对冠瘤海鞘（Styela canopus)幼体附着和变态的影响。在盐度10－40范围内，低盐度抑制幼体变态，高盐度促进其开始变态及完全变态，但盐度40不促进完全变态。低盐度可使幼体附着（除盐度10抑制附着），高盐度促进附着，但盐度达40不促进附着。     

Groundwater Protection and Unconventional Gas Extraction: The Critical Need for Field‐Based Hydrogeological Research

Unconventional natural gas extraction from tight sandstones, shales, and some coal‐beds is typically accomplished by horizontal drilling and hydraulic fracturing that is necessary for economic development of these new hydrocarbon resources. Concerns have been raised regarding the potential for contamination of shallow groundwater by stray gases, formation waters, and fracturing chemicals associated with unconventional gas exploration. A lack of sound scientific hydrogeological field observations and a scarcity of published peer‐reviewed articles on the effects of both conventional and unconventional oil and gas activities on shallow groundwater make it difficult to address these issues. Here, we discuss several case studies related to both conventional and unconventional oil and gas activities illustrating how under some circumstances stray or fugitive gas from deep gas‐rich formations has migrated from the subsurface into shallow aquifers and how it has affected groundwater quality. Examples include impacts of uncemented well annuli in areas of historic drilling operations, effects related to poor cement bonding in both new and old hydrocarbon wells, and ineffective cementing practices. We also summarize studies describing how structural features influence the role of natural and induced fractures as contaminant fluid migration pathways. On the basis of these studies, we identify two areas where field‐focused research is urgently needed to fill current science gaps related to unconventional gas extraction: (1) baseline geochemical mapping (with time series sampling from a sufficient network of groundwater monitoring wells) and (2) field testing of potential mechanisms and pathways by which hydrocarbon gases, reservoir fluids, and fracturing chemicals might potentially invade and contaminate useable groundwater.     

Immiscibility between silicate magmas and aqueous fluids: a melt inclusion pursuit into the magmatic-hydrothermal transition in the Omsukchan Granite (NE Russia)

Exsolution (unmixing) of the volatile element-rich phases from cooling and crystallising silicate magmas is critical for element transport from the Earth’s interior into the atmosphere, hydrosphere, crustal hydrothermal systems, and the formation of orthomagmatic ore deposits. Unmixing is an inherently fugitive phenomenon and melt inclusions (droplets of melt trapped by minerals) provide robust evidence of this process. In this study, melt inclusions in phenocrystic and miarolitic quartz were studied to better understand immiscibility in the final stages of cooling of, and volatile exsolution from, granitic magmas, using the tin-bearing Omsukchan Granite (NE Russia) as an example.

Primary magmatic inclusions in quartz phenocrysts demonstrate the coexistence of silicate melt and magma-derived Cl-rich fluids (brine and vapour), and emulsions of these, during crystallisation of the granite magma. Microthermometric experiments, in conjunction with PIXE and other analytical techniques, disclose extreme heterogeneity in the composition of the non-silicate phases, even in fluid globules within the same silicate melt inclusion. We suggest that the observed variability is a consequence of strong chemical heterogeneity in the residual silicate-melt/brine/vapour system on a local scale, owing to crystallisation, immiscibility and failure of individual phases to re-equilibrate. The possible evolution of non-silicate volatile magmatic phases into more typical “hydrothermal” chloride solutions was examined using inclusions in quartz from associated miarolitic cavities.