UV photolysis, organic molecules in young disks, and the origin of meteoritic amino acids

The origin of complex organic molecules such as amino acids and their precursors found in meteorites and comets is unknown. Previous studies have accounted for the complex organic inventory of the Solar System by aqueous chemistry on warm meteoritic parent bodies, or by accretion of organics formed in the interstellar medium. This paper proposes a third possibility: that complex organics were created in situ by ultraviolet light from nearby O/B stars irradiating ices already in the Sun’s protoplanetary disk. If the Sun was born in a dense cluster near UV-bright stars, the flux hitting the disk from external stars could be many orders of magnitude higher than that from the Sun alone. Such photolysis of ices in the laboratory can rapidly produce amino acid precursors and other complex organic molecules. I present a simple model coupling grain growth and UV exposure in a young circumstellar disk. It is shown that the production may be sufficient to create the Solar System’s entire complex organic inventory within 10⁶ yr. Subsequent aqueous alteration on meteoritic parent bodies is not ruled out.     

Mesoproboloides excavata n. sp. (Amphipoda: Gammaridea: Stenothoidae) from New Zealand

Mesoproboloid.es excavata n. sp. is described and illustrated from material collected at Kaikoura, New Zealand. It differs most conspicuously from the other three known species of the genus in the posterodistally excavate coxa 4, the stout, blunt lobe distally on article 1 of antenna 1, the crenulate ventral margins of coxae 2–4, and the castellate posterior margin of article 2 of pereopod 5. The structure and distribution of minute organs, probably sensory receptors, densely distributed over much, of the integument was examined by scanning electron microscopy. The genus Mesoproboloides is now seen to be cold temperate‐subantarctic in occurrence.     

Crustal deformation effects on the chemical evolution of geothermal systems: the intra-arc Liquiñe–Ofqui fault system,Southern Andes

A better understanding of the chemical evolution of fluids in geothermal and hydrothermal systems requires data-based knowledge regarding the interplay between active tectonics and fluid flow. The Southern Andes volcanic zone is one of the best natural laboratories to address this issue because of the occurrence of numerous geothermal areas, recent seismic activity generated by regional fault systems, and intense volcanic activity. Geothermal systems have been understudied in this area, and limited scientific information exists about the role of local kinematic conditions on fluid flow and mineralization during the development and evolution of geothermal reservoirs. In this study, we provide data for a 1:200,000 scale geological and structural map of the Villarrica–Chihuio area as a setting in which to perform a structural analysis of active geothermal areas. This structural analysis, combined with geochemical modelling of hot spring data, allows the identification of two magmatic-tectonic-geothermal domains based on fault systems, volcanic activity, and lithologies. The Liquiñe–Ofqui fault system (LOFS) domain encompasses geothermal areas located either along the master or subsidiary faults. These are favourably orientated for shear and extension, respectively. In the LOFS domain, the geochemistry of hot spring discharges is controlled by interaction with the crystalline basement, and is characterized by low B/Cl conservative element ratios and high pH. In marked contrast, the arc-oblique long-lived fault systems (ALFS) domain includes geothermal occurrences located on the flanks of volcanoes forming WNW-trending alignments; these systems are built over faults that promote the development of crustal magma reservoirs. Unlike the first domain, the fluid chemistry of these geothermal discharges is strongly controlled by volcanic host rocks, and is typified by lower pH and higher B/Cl ratios. Reaction path modelling supports our model: chemical evolution of geothermal fluids in the Villarrica–Chihuio area is strongly dependent on structurally controlled mechanisms of heat transfer. Within this framework, heat transfer by conduction is responsible for the LOFS domain, whereas magmatically enhanced advective transport dominates heat flow in the ALFS domain. Although more studies are needed to constrain the complex interplay between tectonics and fluid flow, results from this study provide new insights towards efficient exploration strategies of geothermal resources in Southern Chile.     

DMS and its oxidation products in the remote marine atmosphere: implications for climate and atmospheric chemistry

DMS emitted into the atmosphere over the global oceans has a range of effects upon atmospheric composition (mediated through various oxidation products) that may be significant with regard to issues as important as climate regulation, and the trace gas oxidation capacity of the marine atmospheric boundary layer. The roles played by DMS oxidation products within these contexts are diverse and complex, and in many instances are not well understood. Here we summarize what is known, and suspected, about the couplings between the marine atmospheric sulfur cycle, other atmospheric chemical cycles, and the dynamics and microphysics of the marine atmospheric boundary layer. This overview focuses heavily on measurements carried out in clean Southern Ocean air masses in association with the Australian Baseline Air Pollution Station located at Cape Grim (40° 40′ 56″S, 144° 41′ 18″ E), Tasmania. The data confirm that in the remote marine atmosphere, DMS is a central player in a variety of important atmospheric processes, reinforcing the need to understand quantitatively the factors that regulate DMS emissions from the ocean to the atmosphere.     

江西九瑞矿集区成矿与未成矿中酸性侵入岩年代学、岩石化学、矿物化学特征的异同及地质意义

江西九瑞矿集区主要发育有斑岩型、矽卡岩型及块状硫化物型三种类型的铜多金属矿床,其中斑岩型与矽卡岩型为典型的岩浆热液矿床,块状硫化物型矿床产在五通组砂岩与黄龙组白云岩界面之中,但多数也均位于侵入体附近,通常认为岩浆热液对层状黄铁矿体的叠加作用对其成矿起了重要作用。区内同时发育有大量与成矿岩体岩性相似的未成矿侵入岩,长期以来,一直未能找出成矿侵入岩的判别标志和侵入岩成矿与否的原因。本文对区内岩性为花岗闪长斑岩、石英闪长玢岩的成矿与未成矿侵入岩进行了锆石U-Pb定年、岩石主量元素分析以及造岩矿物电子探针测试工作,结果显示,九瑞地区岩浆活动的时代相对集中,成矿侵入岩的年龄分布于138.2±1.8Ma至148.0±1.0Ma之间,未成矿侵入岩的年龄分布于139.0±1.3Ma至149.6±3.0Ma之间,成矿与未成矿侵入岩的侵位时代基本相同,年龄在误差范围内一致。二者的SiO₂以及其它9种主量元素含量的变化范围都非常接近,或有很大重叠,表明成矿与未成矿侵入岩的主要岩石化学成分基本相同。通过造岩矿物成份计算了岩浆开始固结的温度和侵位压力,成矿侵入岩的平均温度769℃与未成矿侵入岩的平均温度723℃在误差范围内大体一致,但成矿侵入岩的温度变化范围（580~915℃）明显大于未成矿侵入岩（656~796℃）。侵位压力方面,未成矿侵入岩的压力值（平均5.7kbar）显著大于成矿侵入岩（平均1.4kbar）。因此我们认为,成矿与未成矿侵入岩相比,前者经历了更为显著的减压过程,该过程也许对形成岩浆热液矿床非常重要,可能是产生独立热液相的一个主要途径,并且能够在岩体内及围岩中造成大量裂隙,为热液循环提供通道。但是,数据同时显示,并非经历了显著减压过程的侵入岩都能够成矿,最终成矿与否是受到不同阶段多种因素联合控制的,因此显著减压并不是成矿的充要条件,而更可能是前提条件。由已获得的未成矿侵入岩数据来推测,在九瑞地区,侵位压力大于4kbar的中酸性侵入岩,成矿潜力可能较小。由黑云母成份估算的氧逸度显示,成矿侵入岩的氧逸度变化较大并且覆盖了未成矿侵入岩的氧逸度范围,但是未成矿侵入岩的氧逸度均没有超过HM（Fe₃O₄-Fe₂O₃）缓冲线,而成矿侵入岩中有一半左右的数据点高于该缓冲线,表明较高的氧逸度对成矿更为有利,在九瑞地区,氧逸度高于HM（Fe₃O₄-Fe₂O₃）缓冲线的侵入岩,其成矿潜力可能更大。     

Prebiotic organic synthesis in early Earth and Mars atmospheres: Laboratory experiments with quantitative determination of products formed in a cold plasma flow reactor

The goal of this study was to explore prebiotic chemistry in a range of plausible early Earth and Mars atmospheres. To achieve this laboratory continuous flow plasma irradiation experiments were performed on N₂/H₂/CO/CO₂ gas mixtures chosen to represent mildly reducing early Earth and Mars atmospheres derived from a secondary volcanic outgassing of volatiles in chemical equilibrium with magmas near present day oxidation state. Under mildly reducing conditions (91.79% N₂, 5.89% H₂, 2.21% CO, and 0.11% CO₂), simple nitriles are produced in the gas phase with yield (G in molecules per 100 eV), for the key prebiotic marker molecule HCN at G∼1×¹⁰⁻³ (0.1 nmol J⁻¹). In this atmosphere localized HCN concentrations possibly could approach the 10⁻² M needed for HCN oligomerization. Yields under mildly oxidizing conditions (45.5% N₂, 0.1% H₂, 27.2% CO, 27.2% CO₂) are significantly less as expected, with HCN at G∼3×¹⁰⁻⁵ (). Yields in a Triton atmosphere which can be plausibly extrapolated to represent what might be produced in trace CH₄ conditions (99.9% N₂, 0.1% CH₄) are significant with HCN at G∼1×¹⁰⁻² (1 nmol J⁻¹) and tholins produced. Recently higher methane abundance atmospheres have been examined for their greenhouse warming potential, and higher abundance hydrogen atmospheres have been proposed based on a low early Earth exosphere temperature. A reducing (64.04% N₂, 28.8% H₂, 3.60% CO₂, and 3.56% CH₄), representing a high CH₄ and H₂ abundance early Earth atmosphere had HCN yields of G∼5×¹⁰⁻³ (0.5 nmol J⁻¹). Tholins generated in high methane hydrogen gas mixtures is much less than in a similar mixture without hydrogen. The same mixture with the oxidizing component CO₂ removed (66.43% N₂, 29.88% H₂, 0% CO₂, and 3.69% CH₄) had HCN yields of G∼1×¹⁰⁻³ (0.1 nmol J⁻¹) but more significant tholin yields.     

岩浆黑云母和热液黑云母矿物化学研究进展

黑云母是岩浆岩和斑岩型矿床中重要的含水铁镁质成岩硅酸盐矿物。黑云母化学成分可以有效地指示岩浆性质、热液蚀变以及成矿过程。文章基于前人和作者的研究成果,系统地总结了黑云母矿物化学在黑云母分类、地质温度计、地质压力计、氧逸度等方面的应用,对岩石成因及构造背景的指示意义,卤素和卤素逸度评价岩浆热液过程,成矿潜力评价等方面的研究新进展,为斑岩型铜多金属矿床的成矿预测和勘查评价提供了最新的找矿矿物学证据。并提出了黑云母矿物化学在研究中存在的一些问题及未来的研究方向。     

七连屿海域表层海水及沉积物重金属环境质量评估

为研究七连屿海洋环境质量状况,于2017年8月在七连屿海域布设20个采样站位,共采集到22个表层海水样品及6个表层沉积物样品,通过原子吸收分光光度计及原子荧光分光光度计测定海水及沉积物中重金属(Cu、Pb、Zn、Cd、Cr、As、Hg)的含量,采用单因子评价法、综合污染指数法及相关性分析对水质重金属污染程度进行研究,并采用单因子评价法及Hankanson潜在生态风险指数法分别对沉积物质量及沉积物中重金属潜在生态风险进行评价。结果表明,2017年七连屿海域表层海水重金属含量CZn>CPb>CAs>CCr>CCu>CCd>CHg,部分站位海水铅含量超一类海水水质标准,但是综合污染指数小于1,该调查海域表层海水属于清洁型;海水中Zn-As、Cr-Cd含量之间存在显著负相关关系,此两组元素存在明显异源性;该调查海域表层沉积物重金属含量均符合第一类海洋沉积物质量标准,沉积物重金属对海洋生态系统仅存在轻微生态风险。     

Major ion chemistry,weathering processes and water quality assessment in upper catchment of Damodar River basin,India

The chemical characteristics of surface, groundwater and mine water of the upper catchment of the Damodar River basin were studied to evaluate the major ion chemistry, geochemical processes controlling water composition and suitability of water for domestic, industrial and irrigation uses. Water samples from ponds, lakes, rivers, reservoirs and groundwater were collected and analysed for pH, EC, TDS, F, Cl, HCO₃, SO₄, NO_3, Ca, Mg, Na and K. In general, Ca, Na, Mg, HCO₃ and Cl dominate, except in samples from mining areas which have higher concentration of SO₄. Water chemistry of the area reflects continental weathering, aided by mining and other anthropogenic impacts. Limiting groundwater use for domestic purposes are contents of TDS, F, Cl, SO₄, NO₃ and TH that exceed the desirable limits in water collected from mining and urban areas. The calculated values of SAR, RSC and %Na indicate good to permissible use of water for irrigation. High salinity, %Na, Mg-hazard and RSC values at some sites limit use for agricultural purposes.