CO2加富对塔玛亚历山大藻叶绿素荧光参数及产毒的影响

由大气中CO_2浓度升高引起的海洋酸化,是全球性的重大环境问题之一。本研究采用实验生态学的方法,以塔玛亚历山大藻(Alexandrium tamarense)为研究对象,分析其在CO_2加富条件下叶绿素荧光动力学参数及产毒特征的变化。调制叶绿素荧光结果显示,CO_2加富对塔玛亚历山大藻的PSⅡ最大光化学量子产量(Fv/Fm)、最大相对电子传递效率(r ETRmax)有显著影响(P0.05),且随着培养时间的增长Fv/Fm、r ETRmax均降低,对半饱和光强(Ik)、快速光曲线初始斜率(α)却无显著影响(P0.05)。结果说明CO_2加富能促进塔玛亚历山大藻的PSⅡ最大光化学量子产量,提高其最大光能转换效率和相对最大电子传递效率。高效液相色谱法分析结果显示,该株塔玛亚历山大藻主要产漆沟藻毒素1(GTX1)、漆沟藻毒素4(GTX4)、N-磺酰氨甲酰基毒素(C1)及N-磺酰氨甲酰基毒素(C2)四种PSTs毒素,CO_2加富不改变主要麻痹性贝毒(PSTs)的种类组成,但能显著提高氨基甲酸酯类毒素(GTX1、GTX4)产量(P0.05),而降低N-磺酰氨甲酰基类毒素(C1、C2)产量(P0.05),说明加富能使塔玛亚历山大藻所产毒素发生转化,进而影响藻细胞的整体毒性。     

Paratacamite from Gypsum Veins in Sandstones of the Kuqa Basin,Xinjiang, China: Implications for a New Epigenetic Cu Enrichment Mechanism

The Kuqa Basin filled with Paleogene evaporite series is located in the northeast of the Tarim Basin, Xinjiang, China. It is famous for sandstone‐hosted Cu deposits formed by synsedimentary processes. However, our recent studies reveal that there has been another Cu mineralization mechanism in this basin. Field investigations show that there is a close relationship among faults, salt domes, and brine. Cu deposits are mainly located in two east–west‐trending anticlinal belts in the basin, adjacent to salt domes in the belts. Cu minerals in gypsum veins of the Jidike and Kangcun formations have been investigated by SEM, EDS, and X‐ray diffraction methods. The occurrence of paratacamite in gypsum veins has been reported to coexist with glauberite and halite in the joint planes of sandstones. In addition, it occurs accompanying residual crystal salt encrustation in limestone fractures, or in sandstones in dendritic form. These features indicate that the surface‐Cu enrichment in the Kuqa Basin might have originated from Cu‐bearing brine in the underlying evaporite units, which migrated upward along fractures. In addition, the presence of H₂S in the east–west fault belt in the Kuqa Basin, and the discovery of surface sulfur, calcium carbonate, and covellite, suggest thermochemical sulfate reduction near salt domes in the deeper parts of the rock units. This process resulted in the generation of reduced brine and provided a favorable environment for Cu enrichment. Therefore, the surface‐Cu mineralization near salt domes is interpreted to be the result of Cu‐bearing brine migrating upward to the surface along faults (or joints) following the intrusion of deep salt domes. The geological evidence indicates the presence of reducing brine and Cu‐bearing brine near the salt dome in the deeper rocks of the Kuqa Basin, thus making the intrusive contact zone of the salt dome a favorable site for the epigenetic enrichment of Cu. Our study demonstrates that Cu enrichment in the Kuqa Basin resulted not only from synsedimentary deposition but also through epigenetic enrichment associated with salt dome intrusion and brine‐rich fluids.     

济宁许厂煤矿伴生分散元素铼的富集成矿探析

铼是一种分散金属,目前尚没有在煤层中富集成矿的案例。该文依据山东省济宁煤田许厂煤矿16上、17煤层光谱分析成果,结合铼元素的性质、物质来源和石炭-二叠纪太原组的聚煤环境等因素进行综合分析,论证了其富集可能性。简要阐述了铼富集成矿的意义,建议煤田地质勘查工作中加强对煤中伴生铼元素的分析和研究。     

Occurrence and Chemical Compositions of Amphiboles in Altered Dioritic Rocks of Laiwu Skarn‐Type Iron Deposit in West Shandong Area,China

The Laiwu Fe deposit is the largest skarn‐type deposit in West Shandong in China, with an estimated reserve of 290 Mt of iron ore. Here, we investigate the occurrence and chemical composition of amphiboles in altered dioritic rocks of this deposit. Three generations of amphibole group minerals were identified in these rocks. The first type (Type 1) is a hornblende with a generally euhedral crystal shape, 150–500 μm in size, and dominantly occurs in the host monzonite. The second type (Type 2) of hornblende occurs as fine grains (<100 μm) or concentric rims, less than 50 μm in thickness, around the Type 1 hornblende. The third type (Type 3) of amphibole is anhedral actinolite occurring along the boundary or the cracks of the Type 1 or 2 hornblende grains. The Type 1 hornblende has higher FeO (12.5–15.6 wt.%) and lower MgO contents (11.2–14.6 wt.%) than the Type 2 hornblende, which has an FeO content ranging from 8.8 to 10.5 wt.% and MgO content ranging from 14.2 to 17.1 wt.%. The Type 3 actinolite shows the lowest FeO (4.6–6.4 wt.%) and highest MgO (19.8–21.2 wt.%) contents. We infer that the Type 2 hornblende formed from Fe‐rich hydrothermal fluids released during rapid upwelling of the crystallizing magma. The fluids were relatively reduced and enriched in Fe. The Type 3 actinolite formed by coupled dissolution and reprecipitation, and its formation is one of the features denoting Fe‐enrichment events. Our study of these types of amphibole provides insights into the ore formation process.     

Origin of natural sulfur-metal chimney in the Tangyin hydrothermal field,Okinawa Trough: constraints from rare earth element and sulfur isotopic compositions

For the first time, we present the rare earth element (REE) and sulfur isotopic composition of hydrothermal precipitates recovered from the Tangyin hydrothermal field (THF), Okinawa Trough at a water depth of 1206 m. The natural sulfur samples exhibit the lowest ΣREE concentrations (ΣREE= 0.65×10^–6–4.580×10^–6) followed by metal sulfides (ΣREE=1.71×10^–6–11.63×10^–6). By contrast, the natural sulfur-sediment samples have maximum ΣREE concentrations (ΣREE=11.54×10^–6–33.06×10^–6), significantly lower than those of the volcanic and sediment samples. Nevertheless, the δEu, δCe, (La/Yb)_N, La/Sm, (Gd/Yb)_N and normalized patterns of the natural sulfur and metal sulfide show the most similarity to the sediment. Most hydrothermal precipitate samples are characterized by enrichments of LREE (LREE/HREE=10.09–24.53) and slightly negative Eu anomalies or no anomaly (δEu=0.48–0.99), which are different from the hydrothermal fluid from sediment-free mid-oceanic ridges and back-arc basins, but identical to the sulfides from the Jade hydrothermal field. The lower temperature and more oxidizing conditions produced by the mixing between seawater and hydrothermal fluids further attenuate the leaching ability of hydrothermal fluid, inducing lower REE concentrations for natural sulfur compared with metal sulfide; meanwhile, the negative Eu anomaly is also weakened or almost absent. The sulfur isotopic compositions of the natural sulfur (δ³⁴S=3.20‰–5.01‰, mean 4.23‰) and metal sulfide samples (δ³⁴S=0.82‰–0.89‰, mean 0.85‰) reveal that the sulfur of the chimney is sourced from magmatic degassing.     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

中国铝土岩系中伴生钪资源富集规律及富集机制初探

钪(Sc)作为新世纪的重要资源,广泛分布于自然界中,但其分布极为稀散,钪的独立矿物稀少,独立矿床几乎没有。铝土岩系中的钪资源储量巨大,本文统计了中国各铝土矿成矿带Sc数据,在对比山西(断隆)成铝区、华北陆块南缘成铝区、渝南—黔北成铝带、黔中成铝区和滇东南—桂西成铝区的数据基础上,发现滇东南—桂西成铝区的Sc含量最高,含钪铝土岩系形成时代主要为石炭纪和二叠纪。通过对比分析A/S与钪的关系,在A/S小于2.5,钪的含量总体较高,且与A/S正相关,大于2.5后,与A/S负相关。从而得出在铝土岩系中,Sc分布在顶层的黏土岩、中部的铁质铝土矿以及底部的铁质黏土岩、铁质岩,尤其是在含铁铝土岩系中高度富集。通过对比分析铝土岩系各元素含量,发现钪与铁、铌、钒、铬元素成正相关,综合铝土岩系中其他元素的矿物表现形式,推测钪在铝土岩系中的赋存形式可能为：类质同象、离子吸附、和超显微非结构混入物。本文初步探讨总结钪在铝土岩系中可能的赋存形式、时空分布规律及钪的迁移转化机制,为铝土矿中伴生钪资源的综合利用开发提供理论支撑。     

鄂尔多斯盆地南部马莲河流域地下水中锶富集特征及成因分析

马莲河流域地处鄂尔多斯盆地南部黄土高原区,按储水介质和埋藏条件可将地下水分为黄土潜水、基岩潜水和基岩承压水三类,利用2015—2018年流域的295组地下水水化学数据,分析了地下水中锶(Sr²⁺)的质量浓度水平、垂向分布及沿流向分布的特征,并采用因子相关性研究地下水中Sr²⁺的来源和富集成因。结果表明:马莲河流域地下水富锶现象显著,黄土潜水、基岩潜水和基岩承压水中锶的平均质量浓度分别为1.14 mg/l、1.39 mg/l和5.24 mg/l;地下水中锶富集成因主要是含锶矿物天然状态下的水-岩作用,黄土潜水、基岩潜水和基岩承压水三类地下水中Sr²⁺的主要来源分别为碳酸盐岩与铝硅酸盐岩、碳酸盐岩与硫酸盐和碳酸盐矿物的溶滤作用;地下水中Sr²⁺的质量浓度沿流向呈逐渐增大的趋势,在不同区域中随深度变化的趋势不一致。     

黔西南水银洞爆破角砾岩筒与金元素超常富集

水银洞金矿床曾被认为是滇黔桂地区最有代表性的微细浸染型金矿(卡林型金矿),然而矿床的金品位明显高于一般意义上的卡林型金矿床,且金矿体与气液爆破角砾岩关系密切.气液爆破角砾岩呈垂直筒状产状,两侧断裂矿化带呈向上扩张的"喇叭口"状成矿空间,富金矿体紧密围绕角砾岩筒分布.根据野外和显微镜观察,角砾岩块成分复杂与显著磨圆.气液角砾岩筒的角砾岩显著富集金、稀土、亲地幔过渡元素Ti、Cr、Ni、Co、V等,以及Zr、Hf等,明显地区别于围岩,反映出深源流体快速上升的气液爆破角砾岩的特征,角砾岩筒实际上具备含金成矿流体的上涌通道的功能.岩筒中早期角砾岩的角砾含Au达18×10–6,属于深部金矿体的爆破碎块,显示出水银洞金矿床可观的深部找矿勘探前景.     

A novel index to evaluate discretization methods:A case study of flood susceptibility assessment based on random forest

The selection of a suitable discretization method(DM)to discretize spatially continuous variables(SCVs)is critical in ML-based natural hazard susceptibility assessment.However,few studies start to consider the influence due to the selected DMs and how to efficiently select a suitable DM for each SCV.These issues were well addressed in this study.The information loss rate(ILR),an index based on the informa-tion entropy,seems can be used to select optimal DM for each SCV.However,the ILR fails to show the actual influence of discretization because such index only considers the total amount of information of the discretized variables departing from the original SCV.Facing this issue,we propose an index,infor-mation change rate(ICR),that focuses on the changed amount of information due to the discretization based on each cell,enabling the identification of the optimal DM.We develop a case study with Random Forest(training/testing ratio of 7:3)to assess flood susceptibility in Wanan County,China.The area under the curve-based and susceptibility maps-based approaches were presented to compare the ILR and ICR.The results show the ICR-based optimal DMs are more rational than the ILR-based ones in both cases.Moreover,we observed the ILR values are unnaturally small(＜1％),whereas the ICR values are obviously more in line with general recognition(usually 10％-30％).The above results all demonstrate the superiority of the ICR.We consider this study fills up the existing research gaps,improving the ML-based natural hazard susceptibility assessments.