Major Element Analyses Research Articles

Constraints on the rollback of the Neo-Tethyan oceanic plate: Geochronology and geochemistry of volcanic rocks from the Dianzhong Formation, western Gangdese belt (Tibetan Plateau)

In this contribution, we report new U-Pb SHRIMP zircon ages and geochemical data for volcanic rocks from the Dianzhong Formation. The unit represents the lower part of the Linzizong volcanic succession located in the Shiquanhe area, western part of the Gangdese belt. Zircon U-Pb dating of three trachytes yields ²⁰⁶Pb/²³⁸U crystallization ages of 71.5±0.6 Ma, 70.8±1.0 Ma and 68.9±1.0 Ma. Whole rock major and trace element analyses indicate a main trend of calc-alkalic to high-potassic calc-alkalic, as well as an enrichment in large ion lithophile elements (LILEs), depletion in high field strength elements (HFSEs), with negative Nb, Ta and Ti anomalies. In addition, these volcanic rocks are enriched in LREE and depleted in HREE without a clear Eu anomaly. These geochemical features are similar to those of active continental margin volcanic rocks. In combination with previously published zircon U-Pb ages and geochemical data of the Dianzhong Formation, we suggest that the Linzizong volcanism started as early as the late Cretaceous (∼71 Ma) and the volcanic rocks of the Dianzhong Formation in the Shiquanhe area are the product of rollback of the Neo-Tethyan oceanic plate.

Controls on the Organic Matter Accumulation of the Marine-Continental Transitional Shanxi Formation Shale in the Southeastern Ordos Basin.

The marine–continental transitional shale with favorable geological conditions for shale gas accumulation and broad resource prospects is widely distributed in China, which is also well developed in the Ordos Basin. The reservoir characteristic and gas-bearing properties of the transitional Shanxi Formation shale have been studied in previous studies. However, the factors influencing the organic matter (OM) accumulation have not been well studied, which restricts shale gas exploration and development of the Shanxi Formation in the Ordos Basin. According to analyses of organic geochemistry, mineral compositions, and major and trace elements, this paper has studied the paleoenvironment characteristic and its influence on the OM accumulation of the Shanxi Formation shale. The results indicate that the OM is characterized by the high mature stage and type III kerogen while the total organic content (TOC) of Member 1 is higher than that of Member 2. From Member 1 to Member 2, the paleowater depth gradually decreases, along with a gradually relative cold and dry climate, decreasing the terrestrial influx intensity and paleoproductivity and increasing the oxygen content in the water column. For Member 1, the OM accumulation is mainly controlled by the terrestrial influx intensity and paleowater depth, and other paleoenvironment factors have an unobvious contribution to the OM accumulation. For Member 2, the OM accumulation is commonly controlled by the weak terrestrial influx, low paleoproductivity, and oxic water column, resulting in the low TOC of Member 2. This study reveals the paleoenvironment characteristic and controls on the OM accumulation of the Shanxi Formation shale, which is beneficial to the reservoir selection of the Shanxi Formation in the southeastern Ordos Basin and the understanding of the OM accumulation in other transitional shales.

Eco-environmental evolutionprocess during the past century in Lake Changdang, Lake Taihu Basin

社会经济转型产生的多重人为驱动力对太湖流域的生态环境和服务功能造成了深远的负面影响.湖泊沉积记录有助于探索流域人与环境长期相互作用过程，为生态修复提供理论支撑.本研究通过对太湖流域长荡湖沉积岩芯有机质、营养盐和重金属元素等指标的系统分析，在²¹⁰Pb定年结果的基础上，结合地球化学标准化方法以及流域人类活动资料，解析了近100年来湖泊的富营养化和重金属污染过程、特征与主要驱动因素.结果显示，长荡湖岩芯沉积指标呈相似的三阶段历史变化，1950s之前，沉积物有机碳、总氮和磷较为稳定，湖泊营养水平较低，对应人类活动影响较弱的准自然演化阶段；随后湖泊进入人为主导的过渡阶段，特别是在1970s，湖泊营养水平、藻类生产力以及重金属污染程度（Cd>>Sb>Cu≈Pb≈Zn）均显著升高，直接受到流域人口增加、农业集约化、工业化和城镇化导致的污染排放的影响.1980s以后，类似于太湖流域大多数湖泊，长荡湖已经大幅偏离自然演化基线，处于高度富营养化、重污染的状态，威胁流域生态安全.本研究进一步指出，深入理解湖泊生态环境历史演变过程及人为影响有助于湖泊-流域系统的可持续管理.;Multiple anthropogenic stressors generated by the socioeconomic transitions have far-reaching negative impacts on the water environment and ecosystem services in the Lake Taihu Basin. Lake sediment records contribute to exploring the interactions between humans and the environment and supporting the ecological restoration in catchments. Based on the analyses of sedimentary organic matter, nutrients and major heavy metal elements in the core of Lake Changdang in the Lake Taihu Basin, combining with ²¹⁰Pb dating results, geochemical normalization and historical documents of human activity in the catchment, this study explored the processes, characteristics and main driving factors of lake eutrophication and heavy metal pollution over the past 100 years. The results show that multiple cores proxies have similar three-stage historical changes. Before the 1950s, sediment organic carbon, total nitrogen and phosphorus were relatively stable, and lake nutrient level was low, corresponding to the quasi-natural evolution phase with the weak influence of human activities. Subsequently, the lake entered into a transition phase dominated by human impacts. Particularly in the 1970s, lake nutrient level, algal productivity and heavy metal pollution (Cd>>Sb>Cu≈Pb≈Zn) increased significantly, which were directly affected by the pollutant discharge resulted from the increase in population, agricultural intensification, industrialization and urbanization in the catchment. Since 1980s, Lake Changdang has deviated from the natural evolution baseline and maintained a state of high eutrophication and heavy pollution, threatening the ecological security of the catchment. This study further highlights that understanding the historical process of lake eco-environmental evolution and anthropogenic impacts helps sustainable lake catchment management.

Geochemistry of Mafic Rocks from the Birimian Basement of Doropo (Northeast of Côte d’Ivoire): Petrogenetic and Geodynamic Implications

The northeastern region of Côte d’Ivoire is characterised by a granitic basement mainly composed of biotite granite rocks. According to mapping work in the Gbabédjou and Doropo areas, these Birimian granitoids are cut by gabbro dykes and amphibolite enclaves, which are the subject of this study. In order to better understand the role and the implication of mafic rocks in the Doropo basement emplacement, a multidisciplinary methodology integrating microscopic observations and geochemical analyses of major and trace elements was carried out on 4 samples considered representative of the outcrops studied. Green hornblende, clinopyroxene, and accessory sphene minerals are found in mafic mineral phases, according to petrographic research. Whole-rock analyses reveal that mafic samples with TiO2 contents 1.1 ratios giving them an orogenic granite nature (I-type). Their REE patterns are moderately fractionated (La/Sm)N = 2.66 - 6.13 and (La/Yb)N = 11.17 - 43.70) with a very negative Eu anomaly (Eu/Eu* = 0.75 - 0.97). The multi-element diagrams are characterized by negative Nb-Ta anomalies and geotectonic studies have identified them as volcanic arc formations. All these characteristics allowed us to distinguish the Doropo mafic rocks as formations originating from the juvenile continental crust, emplaced under the Archean tectonics model with significant crustal contamination in the source. Magma driven by mantle diapir has been injected at the base of the continental crust and the heat induces the partial melting of the overlying crust giving rise to mixed liquids. This magma now enriched in LILE was immediately drained to the upper crust to form the mafic rocks from the studied area.

Long or short silicic magma residence time beneath Hekla volcano, Iceland?

Timescales of magma transfer and differentiation processes can be estimated when the magma differentiation mechanism is known. When conventional major and trace element analyses fail to distinguish between various processes of magma differentiation, isotope compositions can be useful. Lower Th isotope ratios in silicic relative to basaltic magmas at a given volcano could result from magma storage over a period of several tens of thousands of years, or if the differentiation process was fractional crystallization alone, or from crustal anatexis on a much shorter timescale. Recently mapped bimodal tephra layers from Mt. Hekla, Iceland, confirm lower (230Th/232Th) and higher Th/U in silicic versus mafic magmas. Higher Th/U has been taken to indicate either apatite fractionation or partial crustal melting. In situ trace element analysis of apatite and the enveloping glass in basaltic andesite, dacite and rhyolite was undertaken to examine its capacity to fractionate trace elements and their ratios. Both Th and U are compatible in apatite with a partition coefficient ratio DU/DTh of 1. Hence, apatite crystallization and separation from the melt has a negligible effect on Th/U in Hekla magmas. Partial melting of hydrothermally altered crust remains the preferred mechanism for producing silicic melt beneath Hekla. Ten to twenty percent partial melting of metabasaltic crust with 0.4–1.2 wt% H2O produces dacite magma with 4–6% water. Absence of low δ18O values in Hekla magmas compared to silicic magmas of the rift zones suggests mild hydration of the hydrothermally altered crust. Silicic magma formation, storage, differentiation and eruption at Hekla occurred over a timescale of less than a few centuries. Decreasing production of rhyolite and dacite during the Holocene lifetime of Hekla suggests changes in the crustal magma source and readjustment of the magma system with time.

Analysis and application of yttrium element in garnet by electron micro-probe analyzer: A case study of garnet-mica schist from Foziling Group

石榴石是最重要的造岩矿物之一，通常能够保留早期的矿物结构和物质并记录较为晚期的变形和变质反应。石榴石钇（Y）元素环带特征丰富、复杂，不同的环带特征通常暗示不同的形成环境或经历了不同的变质事件，是变质演化历史研究的重要媒介之一。以往的研究中，多以LA-ICP-MS作为石榴石Y元素的主要分析手段，EPMA主要用于主量元素的分析。但是，LA-ICP-MS的束斑尺寸（44μm）和基底效应较EPMA （0~5μm）大，当石榴石颗粒小、包体和裂隙发育或成分环带以微区尺寸内存在较大变化时，大束斑更容易覆盖某些特殊信息。通过对石榴石Y元素测试参数的调试和标样验证，最终确定峰位测试时长和背景测试时长分别为140s和70s，并进行了PHA谱峰干扰剥离，降低检测限至54×10^-6。本文将通过对比佛子岭石榴云母片岩（LD025）4颗石榴石的EPMA主、微量原位分析（Ca、Mg、Mn、Fe、Y、Al、Si、Cr、Ti、Na）和LA-ICP-MS石榴石Y元素分析结果，论证EPMA分析Y元素的可行性。石榴石X-ray Mapping和主量成分剖面揭示该4颗石榴石均为生长环带，Mn呈钟形分带，Y与XSps呈强烈正相关性，与XGrs、XAlm、XPrp相关性不清晰。EPMA和LA-ICP-MS分析结果显示Y含量曲线在核部和幔部具有良好的一致性，Grt1~Grt3中Y均表现出自核部（500×10^-6~1200×10^-6）向幔部（200×10^-6~500×10^-6）逐渐降低，极边部Y含量低（20×10^-6~200×10^-6）且变化复杂；Grt4中Y含量差异相对较小（180×10^-6~450×10^-6），仅在边部出现不同程度的升降。因EPMA对于Y元素含量较低（<200×10^-6）时灵敏度不够或者LA-ICP-MS束斑尺寸大容易掩盖边部窄带成分真实变化等原因，二者在边部Y元素差异较大。分别对EPMA和LA-ICP-MS的分析结果应用Grt-Xtm温度计和Grt单矿物压力计获得的变质PT结果显示Grt1~Grt3（核-幔-边）和Grt4（核-边）均记录较为完整、统一的温压演化过程。M1→M2→M3的变质温压变化分别为T=530~544℃、P=0.78~0.82GPa→T=577~616℃、P=0.89~0.98GPa→T=631~661℃、P=1.01~1.07GPa，表现为顺时针演化型式，M1至M3反映的是一个暖俯冲过程。根据温度评价结果，Grt1~Grt3（1.2~1.4mm，自形程度高）形成时间应早于Grt4（0.8mm，自形程度低）。由此可知，大颗粒的石榴石Y元素含量及变化特征通常更容易揭示相对完整的变质演化历史。本次研究为变泥质岩演化历史、变质温压评价等研究提供了不同视角和思路，结合EPMA主量（矿物成分、X-ray mapping、BSE分析）和微量元素（Y等）分析能够更加精准、全面地解读地质信息。;Garnet is one of the most rock-forming mineral in the earth, it can record not only the former mineral's composition and structure, but also later deformation history and metamorphic reactions of rocks. In previous studies, LA-ICP-MS was mostly used as the main analysis method of yttrium (Y) in garnet, and EPMA was mainly used for analysis of major elements. However, the beam spot size (44μm) and basement effect of LA-ICP-MS are larger than those of EPMA (0~5μm). When garnet particles are small, inclusions and fractures are developed, or there are large changes in the micro area size of the composition ring, the large beam spot is easier to cover some special information. Through the debugging of garnet Y analysis parameters and standard sample verification, it is finally determined that the peak position and background counting time are 140s and 70s respectively, and the PHA spectrum peak interference stripping is carried out to reduce the detection limit to 54×10^-6. The paper will demonstrate the feasibility of EPMA analysis of Y by comparing the results of EPMA main and micro in-situ analysis (Ca, Mg, Mn, Fe, Y, Al, Si, Cr, Ti, Na) and LA-ICP-MS garnet Y content analysis. Garnet X-ray mapping and component profile reveal that the four garnets are characterize by growth ring, and the bell shaped zoning of Mn is typical. Among them, Y has a strong positive correlation with XSps, and the correlation with XGrs, XAlm and XPrp is not clear. The results of EPMA and LA-ICP-MS analysis show that the Y content curves are in good agreement both core and rim. Yttrium in Grt1~Grt3 is characterized by a gradual decrease from the core (500×10^-6~1200×10^-6) to the mantle (200×10^-6~500×10^-6), the extreme rim with low Y (20×10^-6~200×10^-6) and the change is complex. The difference of Y content in Grt4 is relatively small (180×10^-6~450×10^-6), and there are only different degrees of rise and fall at the outer edge. Due to the insufficient sensitively of EPMA to low Y content (<200×10^-6) or the large beam spot size of LA-ICP-MS, which is easy to cover up the real change of narrow rim Y composition, the two have great differences Y contents in the rim section. Based on the analysis results of EPMA and LA-ICP-MS, the metamorphic PT conditions obtained by Grt-Xtm thermometer and Grt single mineral geobarometer show that Grt1~Grt3 (core-mantle-rim) and Grt4 (core-rim) record a relatively complete and unified metamorphic PT evolution process. The metamorphic PT changes of M1→M2→M3 are T=530~544℃and P=0.78~0.82GPa→T=577~616℃ and P=0.89~0.98GPa→T=631~661℃ and P=1.01~1.07GPa respectively, showing a clockwise evolution pattern. M1 to M3 reflect a warm subduction process. According to the PT results, the formation time of Grt1~Grt3 (1.2~1.4mm, high automorphism) should be earlier than Grt4 (0.8mm, lower automorphism). Therefore, the content and variations characteristics of Y in large grain garnet are usually easier to reveal the relatively complete metamorphic evolution process. This study provides different perspectives and ideas for the study of metamorphic argillaceous rock evolution history and metamorphic temperature. Combined with EPMA major element (composition, X-ray mapping and BSE analysis) and trace element (Y, etc.) analysis, the geological information can be interpreted more accurately and comprehensively.

Petrography, Geochemistry and Petrogenesis of the Basalt Flow at Al Azraq Al Shamali Area, East Jordan

Al Azraq Al Shamali (AZS) basaltic rocks were investigated aiming to understand their mineralogy, petrography and geochemistry features, and to achieve that a total of sixteen representative rock samples were selected for both geochemical and petrographic analysis from several sites in the study area. Petrographic characteristics were analyzed by optical microscopy after preparation thin sections for representative rock samples, which show that all basalt samples have minerals comprising: olivine, plagioclase (labradorite), clinopyroxene (augite), opaque’s and some secondary minerals such as Iddingsite, however, the proportions of each mineral vary between samples. Normative mineralogy by using CIPW Norm showed that AZS basalt samples dominated by olivine, Diopside, and nepheline, and AZS basalt can be normatively classified as alkali olivine basalt. Some textures that may be evident on microscopic examination such as porphyritic, glomeroporphyritic, vesicular, intergranular, and ophitic to sub-ophitic texture. X-Ray Fluorescence was used for whole rock major elements analysis (SiO2, TiO2, Al2O3, Fe2O3, MnO, MgO, CaO, Na2O, K2O and P2O5 in wt%) and trace element (V, Cr, Co, Ni, Rb, Sr, Y, Zr, Nb, Ce, Nd and Ba in ppm). Geochemical analysis reveal that the basalt is alkaline and includes into Sodic series. AZS basalt are produced under-saturated within intraplate continental environment. The normalized trace element diagrams suggest that the AZS product of the asthenosphere part of the mantle at >100 km depth. Furthermore, the data of studied samples suggest that these rocks evolved from a melt formed by low degrees of partial melting. Also the geochemical variation trends of (AZS) basaltic samples supposing that the composition of these basalt have been influenced by fractional crystallization, without clear evidences for crustal contamination.

A Study on Manufacturing Technique and Alloy Characteristics of Bronze Mirrors from Jeollanam-do Region in the Three Kingdoms Period

This study analyzed the microstructures and chemical composition of three samples of bronze mirrors excavated in the Jeollanam-do region, particularly Goheung and Damyang. Under x-ray irradiation, the analysis results confirmed the broken parts and pores caused by cracks, casting, and corrosion. Major and minor elemental analysis were performed on three mirrors by Scanning electron microscopy (SEM) with Energy dispersive x-ray spectrometry (EDS) and Inductively coupled plasma mass spe ctrome try (ICP-MS). The re sult shows that the bronze mirrors containe d Cu-Sn-Pb alloys. Alpha phase and eutectic phase were observed in the microstructure, confirming that the casting was performed without additional heat treatment. Notably, Three bronze mirrors were made early Three Kingdoms period in Korea.

Chemical and Isotopic Tracers for Characterization of the Groundwater in the Heterogeneous System: Case from Chichaoua-Imin’tanout (Morocco)

The geological and hydrogeological approach of the structure of the basin OuladBouSbaâ led to the definition of the geometry of the main aquifers. In general, the profiles show the complexity of the geological configuration. The filling of the depression of OuladBouSbaâ is from the Eo-Cretacian. At this level, the aquifer is recharged by direct water infiltration. The quaternary, Eocene, and Cenomanian-Turonian formations constitute the main aquifers. Horizontal as well as vertical heterogeneity lead to a higher diversification of aquifer characteristics. To define the origins and understand the groundwater flows in this complex zone, we used a multi-tracer approach with the analysis of major elements and the isotopes of δ2H and δ18O. The chemical composition is mainly governed by the interaction with the rock with low electrical conductivity except in areas around domestic landfills. Geochemical results analyzing groundwater in the Piper diagram show two distinct chemical facies: the sulfated calcium and magnesium, and the hyper-chloride calcium. The levels of δ18O range from −7.60 to −4.25 while those of δ2H vary between −53.07 and −27.03. Analyses of signature isotopes differentiate two groups. The first contains high levels of heavy isotopes (highest levels of δ2H and δ18O) having therefore been submitted to evaporation. The second with lower levels of δ2H and δ18O did not undergo evaporation. The first one belongs to the unconfined free aquifer while the second corresponds to the captive aquifer.

Formation of Late Ordovician marine red beds: A case study of Sandbian deposits in the Tarim Basin, Northwest China

The late Ordovician was an important transition interval between the mid-Ordovician biological radiation and end-Ordovician extinction. Marine red beds (MRB) of Late Ordovician are distributed worldwide, including in the Americas, South Africa, England, and China. Among them, the conditions that contributed to the widespread Katian MRB was a combination of terrigenous input, cool-water settings, sediment oxidation, volcanic material input, and seasonal aridity. In contrast, Hirnantian MRB have a more limited distribution, and their occurrence might be related to regional tectonic settings and icehouse conditions. Sandbian MRB are distributed worldwide, but are relatively poorly studied. Even though Sandbian MRB are very similar in some characteristics to the Katian MRB, we don't know which factors were important to their formation and how these were related to marine environmental change and tectonic evolution. The Dawangou section near Kalping in the Tarim Basin of northwest China is an important global reference section for the auxiliary GSSP of the Middle–Late Ordovician boundary and for Sandbian through early Katian biostratigraphy and chronostratigraphy. Diffuse reflection spectroscopy, major and trace element analysis, rare earth element analysis, and sedimentology were employed to study the interval of Sandbian MRB in the Kanling Formation (within the N. gracilis graptolite zone) relative to underlying and overlying deposits. The red-colored strata have elevated total Fe and hematite contents, whereas the grey and grey-green samples have much a lower total Fe and a significant lack of hematite and goethite. The total Fe content for strata within the Sandbian MRB varies with the clay content. The AlFe correlation within the Sandbian MRB is 0.9, whereas it is 0.6 for the non-red sediments. The Th/U ratio is much higher in the red-colored beds (averaging 7.0) relative to the underlying and overlying sediments (averaging 4.4). However, a redox proxy of Ni/Co ratios does not exhibit a significant difference between the underlying and overlying sediments (averages of 2.6 and 2.8) and the reddish Sandbian MRB interval (average of 2.6). The results indicated that the Sandbian marine red beds of the Tarim were formed during conditions of marine oxygenation that helped form and preserve the iron oxide. However, the regional distribution and aspects of the sediment geochemistry imply that another essential process for the formation of these Sandbian MRB was the influx of terrestrial iron-rich sediments from the exposed uplifts into the mixed shelf regions; and that this influx was partly governed by the regional patterns of southward subduction of the South Tianshan ocean and of northward subduction of the Altyn to the margins of the Tarim block.

Carbonate Mineralogy in Mantle Peridotites of the Atlantis Massif (IODP Expedition 357)

AbstractPetrographic and major element investigations of carbonates from seven drill cores recovered during IODP Expedition 357 on the Atlantis Massif (AM) provide information on the genesis of carbonate minerals in the oceanic lithosphere. Textural sequences and mineralogical assemblages reveal three distinct types of carbonate occurrences in ultramafic rocks that are controlled by (a) fluid composition and flow, (b) temperature, and (c) the presence of mafic intrusions. The first occurrence of carbonate consists of different generations of calcite that formed syn‐ to post‐ serpentinization. These calcites formed at temperatures between 30 and 184°C (based on clumped isotope thermometry) and from a fluid influenced by interaction with mafic intrusions. The second occurrence consists of magnesite, dolomite, calcite, and aragonite veins that also formed syn‐ to post serpentinization. These carbonates formed at temperatures between ambient and 196°C, from fluids with highly variable FeO, MnO, and SrO composition and Mg/Ca ratios, but overall high CO2 and moderate SiO2 concentrations. High FeO (3.3 wt%) and MnO (7.3 wt%) contents indicate high temperatures, high water/rock ratios, and low oxygen fugacity for both carbonate assemblages. The third occurrence consists solely of aragonite veins formed at low temperatures (&lt;9°C) within the uplifted serpentinized peridotites. Major element analyses suggest that aragonite precipitated from seawater, which experienced little interaction with the basement. Combining these results, we propose a model that positions different carbonate occurrences in a conceptual framework considering mafic domains in the peridotites and fluid heterogeneities during progressive exhumation and alteration of the AM.

Lithofacies Types, Assemblage Characteristics, and Sedimentary Evolution Model of Lacustrine Shale in Dongyuemiao Formation of Fuxing Area

The identification and classification of lithofacies’ types are very important activities in shale oil and gas exploration and development evaluation. There have been many studies on the classification of marine shale lithofacies, but research on lacustrine shale lithofacies is still in its infancy. Therefore, in this study, a high-resolution sequence stratigraphic framework is established for the lacustrine shale of the Jurassic Dongyuemiao Formation in the Fuxing area using detailed core observations, thin section identification, XRD analysis, major and trace element analysis, wavelet transform analysis, and detailed identification and characterization of the fossil shell layers in the formation. In addition, the lithofacies’ types and assemblages are identified and characterized, and the lithofacies’ characteristics and sedimentary evolution models in different sequence units are analyzed. The significance of the lithofacies assemblages for shale oil and gas exploration is also discussed. The results show that the shale of the target interval can be divided into 8 parasequence sets; further, 9 types of lithofacies and 6 types of lithofacies assemblages are identified. The 9 lithofacies are massive bioclast-containing limestone shoal facies (LF1), thick-layered fossil shell–containing limestone facies (LF2), layered mud-bearing fossil shell–containing limestone facies (LF3), laminated fossil shell–containing argillaceous shale facies (LF4), laminated fossil shell–bearing argillaceous shale facies (LF5), argillaceous shale facies (LF6), massive storm event–related bioclast-containing facies (LF7), massive argillaceous limestone facies (LF8), and massive mudstone facies (LF9). The sedimentary evolution models of different lithofacies are established as follows: Unit 1 (LF1-LF6) of the Dong-1 Member corresponds to the early stage of a lake transgressive system tract, and Units 2–4 (LF4-LF7) correspond to the middle to late stage of the lake transgressive system tract, which was an anoxic sedimentary environment. The Dong-2 Member (LF7-LF8) and the Dong-3 Member (LF5+LF9) correspond to a lake regressive system tract, which was an oxygen-rich sedimentary environment. Based on the characteristics of the shale lithofacies, sedimentary environment, and the quality of the reservoir, the lithofacies assemblage of LF4–LF7 in Unit 4 is the most favorable type for oil and gas exploration, followed by the lithofacies assemblage in Unit 2; the lithofacies assemblage in the Dong-2 and Dong-3 Members are the worst.

Proposing a new strategy to minimize domestic wastewater under the influence of human factor in Antananarivo, Madagascar

Water pollution happens when organic or inorganic materials, even solid materials are poured into the water which degrades its physicochemical quality. The purpose of this study is, to identify, to describe and to highlight the major source of wastewater, and proposing a new strategy for minimization in Antananarivo, Madagascar. Antananarivo is one of the dirtiest cities on the African continent according to the classification made by Forbes magazine and Afrikmag. To know the current situation, an in-situ analysis of the physical parameters: colour, odour, turbidity and electrical conductivity using the turbidimeter and the conductometer are measurable parameters in the field. Major elements analyses, BOD5 using Oxytop method analysis, COD using Potassium dichromate, suspended solids using membrane filtration are measured in the laboratory. The turbidity of the discharges fluctuates from 127 NTU to 421 NTU). For electrical conductivity, it varies from 217 to 977μS.cm−1, BOD5 is of the order 3 to 88mg.L−1, while COD diverges from 279mg.L−1 to 730mg.L−1 and suspended matter oscillates from 400mg.L−1 to 60mg.L−1. Some parameters and concentrations exceeded the discharge standard Malagasy and the international Standard. The best solution for the management of water quality in the face of domestic pollution is the treatment of wastewater before discharge into receiving environments and the sensibilization of the population to take their responsibility.

Effect of surface weathering on portable X‐Ray fluorescence analysis of artefacts: Evidence from Tasmanian hornfels

AbstractHornfels was commonly utilised by Aboriginal people in southeastern Tasmania for stone artefact manufacture. Sourcing of hornfels artefacts in this region using pXRF analysis is potentially compromised by the weathering patina generally present on this lithology. To understand the impact of weathering on hornfels composition, the mineralogy and chemical composition of weathered and unweathered hornfels were analysed, and weathering was simulated in column experiments. The results demonstrate that the cordierite and, to a lesser extent, plagioclase present in the hornfels transform very rapidly into kaolinite, which is the dominant component of the pale, porous weathering patina. Weathering simulation experiments and isocon comparisons of major and trace element analyses show that this alteration is accompanied by a substantial loss of Mg, Na and Ca (≥50%). For the trace elements, 25%–35% are removed (except Zr, which is relatively immobile), with the remainder retained in unaltered minerals or adsorbed to the neoformed kaolinite. Rb and Nb are more stable than Sr, which demonstrates the highest absolute mobility, but even this element shows relatively little loss, provided that the weathering patina is &lt;1 mm thick. For Rb, Sr, Y, Zn and Nb, the percentage loss during weathering is similar (25%–35%), so bivariate plots of these trace elements show a spread due to weathering, but with a more or less constant ratio. As a result, pXRF analyses of these elements can be used to successfully differentiate hornfels artefacts from different sites in southeastern Tasmania. This study showed that Rb, Sr, Y and Nb, which are commonly used to source igneous artefacts, are also effective in sourcing hornfels, even though they are mobile during weathering. This study also demonstrated the importance of isocon plots in identifying the trace elements best suited to artefact sourcing using pXRF, if the analyses are affected by chemical weathering.

Controls on Organic Matter Accumulation of the Triassic Yanchang Formation Lacustrine Shales in the Ordos Basin, North China.

Lacustrine shales in the third submember of the Chang7 (Chang73) of the Triassic Yanchang Formation have the highest oil and gas generation potential in the Ordos Basin, North China. To unravel factors governing organic enrichment within this submember, Rock-Eval pyrolysis, major and trace elemental analyses, and molecular composition of extractable organic matter were applied for redox condition, paleosalinity, dilution effect by terrestrial input, paleoproductivity, and paleoclimate condition investigation. The total organic carbon (TOC) contents of the Chang73 organic-rich lacustrine shales show a tripartite feature and can be divided into the upper organic-rich section (UORS, average TOC 6.8 wt %), the middle organic-lean section (MOLS, average TOC 3.5 wt %), and the lower organic-rich section (LORS, average TOC 6.7 wt %). The variation of the productivity-related paleoclimate is likely the main driving force leading to the change of organic richness within the Chang73 submember. The MOLS was deposited under a relatively hot and arid climate (high Sr/Cu but low Rb/Sr values) with lower paleoproductivity (low Porg/Ti and Porg values). Additionally, clastic dilution may further reduce the TOC content to a certain extent in the MOLS. The UORS and LORS, however, were deposited under a warm and humid climate, which leads to enhancement of chemical weathering (high Ln(Al2O3/Na2O) values), increased nutrient input, and elevated paleoproductivity. Furthermore, paleoproductivity of UORS and LORS was further boosted by additional key nutrients, such as Fe and P2O5, provided by syn-depositional volcanic ash. Both paleoredox (U/Th, Corg/P, and Pr/Ph) and paleosalinity (Sr/Ba, gammacerane index) proxies suggest no noteworthy variation of redox and salinity conditions throughout the Chang73 interval.

Petrography and geochemistry preliminary study of Pucangan Serpentinite Geosite Karangsambung – Karangbolong Geopark Central Java, Indonesia

Geosite is a Geological Heritage object in the Geopark area with specific characteristics and is an integral part of the evolutionary history of forming an area. Serpentinite Pucangan is one of the Geosite located in Karangsambung – Karangbolong geopark. This study aims to find out the characteristics of petrography and geochemistry of Serpentinite Pucangan Geosite. The methods used in this study include literature studies, fieldwork research, petrography analysis, ore microscopy analysis, whole rock analysis consist of major element analysis using fusion inductively coupled plasma (Fus ICP) methods, trace element analysis, and rare earth element analysis using inductively coupled plasma mass spectrometry (ICP-MS) methods. Serpentine minerals with antigorite type dominate the petrography composition of Pucangan serpentinite with a little magnetite mineral. SiO2, MgO, and Fe2O3(t) are the major elements with the largest percentage of 37.93%, 5.78%, and 9.73% that have an agreement with the mineralogical composition of the rock that dominated by ferromagnesian minerals. This Geosite is interpreted to be formed due to the metasomatic process when the subduction process is happening in this area in the Pre-tertiary period.

TephraNZ: a major- and trace-element reference dataset for glass-shard analyses from prominent Quaternary rhyolitic tephras in New Zealand and implications for correlation

Abstract. Although analyses of tephra-derived glass shards have been undertaken in New Zealand for nearly four decades (pioneered by Paul Froggatt), our study is the first to systematically develop a formal, comprehensive, open-access reference dataset of glass-shard compositions for New Zealand tephras. These data will provide an important reference tool for future studies to identify and correlate tephra deposits and for associated petrological and magma-related studies within New Zealand and beyond. Here we present the foundation dataset for TephraNZ, an open-access reference dataset for selected tephra deposits in New Zealand. Prominent, rhyolitic, tephra deposits from the Quaternary were identified, with sample collection targeting original type sites or reference locations where the tephra's identification is unequivocally known based on independent dating and/or mineralogical techniques. Glass shards were extracted from the tephra deposits, and major- and trace-element geochemical compositions were determined. We discuss in detail the data reduction process used to obtain the results and propose that future studies follow a similar protocol in order to gain comparable data. The dataset contains analyses of glass shards from 23 proximal and 27 distal tephra samples characterising 45 eruptive episodes ranging from Kaharoa (636 ± 12 cal yr BP) to the Hikuroa Pumice member (2.0 ± 0.6 Ma) from six or more caldera sources, most from the central Taupō Volcanic Zone. We report 1385 major-element analyses obtained by electron microprobe (EMPA), and 590 trace-element analyses obtained by laser ablation (LA)-ICP-MS, on individual glass shards. Using principal component analysis (PCA), Euclidean similarity coefficients, and geochemical investigation, we show that chemical compositions of glass shards from individual eruptions are commonly distinguished by major elements, especially CaO, TiO2, K2O, and FeOtt (Na2O+K2O and SiO2/K2O), but not always. For those tephras with similar glass major-element signatures, some can be distinguished using trace elements (e.g. HFSEs: Zr, Hf, Nb; LILE: Ba, Rb; REE: Eu, Tm, Dy, Y, Tb, Gd, Er, Ho, Yb, Sm) and trace-element ratios (e.g. LILE/HFSE: Ba/Th, Ba/Zr, Rb/Zr; HFSE/HREE: Zr/Y, Zr/Yb, Hf/Y; LREE/HREE: La/Yb, Ce/Yb). Geochemistry alone cannot be used to distinguish between glass shards from the following tephra groups: Taupō (Unit Y in the post-Ōruanui eruption sequence of Taupō volcano) and Waimihia (Unit S); Poronui (Unit C) and Karapiti (Unit B); Rotorua and Rerewhakaaitu; and Kawakawa/Ōruanui, and Okaia. Other characteristics, including stratigraphic relationships and age, can be used to separate and distinguish all of these otherwise-similar tephra deposits except Poronui and Karapiti. Bimodality caused by K2O variability is newly identified in Poihipi and Tahuna tephras. Using glass-shard compositions, tephra sourced from Taupō Volcanic Centre (TVC) and Mangakino Volcanic Centre (MgVC) can be separated using bivariate plots of SiO2/K2O vs. Na2O+K2O. Glass shards from tephras derived from Kapenga Volcanic Centre, Rotorua Volcanic Centre, and Whakamaru Volcanic Centre have similar major- and trace-element chemical compositions to those from the MgVC, but they can overlap with glass analyses from tephras from Taupō and Okataina volcanic centres. Specific trace elements and trace-element ratios have lower variability than the heterogeneous major-element and bimodal signatures, making them easier to fingerprint geochemically.

Surface hydrographic changes at the western flank of the Sicily Channel associated with the last sapropel

In the eastern Mediterranean Sea, the early Holocene was characterized by major climatic and oceanographic changes that led to the formation of the last sapropel (S1) between 10.8 and 6.1 kyr cal. BP. These hydrographic changes might have altered the water exchange between the eastern and western Mediterranean sub-basins through the Strait of Sicily, but the existing evidences are inconclusive. In the present study we show new evidence from sediment core NDT-6-2016 located at the western flank of the Sicily channel, a key location to monitor the surface/intermediate water exchange between the two Mediterranean sub-basins. We perform paleo-hydrographic reconstructions based on planktic foraminifera ecology for the last 15 kyr cal. BP, including the S1 deposition interval. In addition, δ 18 O measurements in both Globigerina bulloides and Globigerinoides ruber and also major elements analyses in bulk sediment are presented. Our results show that significant changes in surface water properties occurred in W-Sicily characterized by a strong contrast in the seasonal hydrographic conditions during the S1 interval. This study proposes that the oceanographic changes in the eastern Mediterranean associated with the surface freshening promoted by the African monsoon likely triggered a restricted water exchange through the Strait of Sicily. This situation led to limited influence of the surface Atlantic waters into the studied area that favored the development of intense summer stratification and vertical winter mixing. This situation changed at about 7 kyr cal. BP when a decrease in the summer stratification probably reflected the influence of the eastward path of the surface Atlantic Waters. This situation would suggest a reinforcement of the water exchange through the Strait of Sicily that marked the end of the extreme conditions that prevailed in the eastern Mediterranean during the S1 formation. • Surface hydrographic reorganization related to the sapropel S1 is observed for the first time in the central Mediterranean. • The acquired data provide new evidences of a restricted sea surface water exchange during the S1 across the Strait of Sicily. • Paleo-hydrographic reconstructions are based on planktic foraminifera ecology, major element analyses and δ 18 O measurements.

ASSESSMENT OF METAL POLLUTION IN INTER TIDAL AND BEACH SEDIMENTS ALONG NORTH EAST COAST OF TAMILNADU, INDIA

The concentrations of major (Al, Fe, Mg, Mn, Na, K and Ca) and trace (Cr, Cu, Ni, Pb and Zn) elements have been determined in inter tidal and beach surface sediments samples collected from North east coast of Tamilnadu, India. Major element analysis showed that the sediments had low concentrations when compared with crustal average and upper continental crust. Using sediment quality guidelines and different types of indexes, current trace elements pollution status in the study area were assessed. Sediment quality guidelines suggest that nickel and lead must be considered as a chemically potential concern in the study area. The indexes used in this study were enrichment factor, geo-accumulation index and modified degree of contamination. Different indexes gave diverse status of inter tidal and beach sediment quality. The results are discussed in the context of the sources and pathways of trace elements in the North east coast of Tamilnadu, India.

An Attractive Blue Diopside from Sissone Valley, Western Alps, Italy

In this work a rare and attractive blue diopside present in Sissone valley in the Western Alps was investigated through different methodologies: geological survey; standard gemological methods; X-Ray Powder Diffraction; SEM observations; Raman spectrometry; EMP analyses of major elements; and LA-ICP-MS analyses for minor and trace elements. The host rock of investigated gems is represented by a Mg-calcite bearing marble, belonging to the Suretta nappe and composed of blue diopside, lizardite, phlogopite, forsterite, Ca-Mg-amphibole, and thomsonite; the rock was metamorphosed by the intrusion of Masino-Bregaglia pluton. The diopside is generally found in the core of veins in contact with green–blue tremolite and, more externally, with green–yellowish lizardite. The diopside samples show opaque diaphaneity, are inert to long and short-waves UV radiation, and their specific density varies between 3.24 and 3.30 g/cm3 while medium refraction between 1.680–1.683. The diopside shows a polycrystalline texture with interstitial Mg-calcite which acts as binder. The characteristic blue–turquoise color is mainly determined by traces of V and subordinately of Fe, Mn, Cr and Ti. The contents of V and Ti show a good positive correlation. The minerals associated with diopside in the lenticular veins also show enrichments in V. The blue diopside of the Sissone valley could certainly present a good commercial value, but unfortunately it is difficult to reach the outcrop sites.