Acta Geochimica最新文献

{"title":"Origin and geochemical characteristics of beryllium mineralization in the Zabara-Wadi El Gemal region, South Eastern Desert, Egypt","authors":"Gehad M. Saleh,&nbsp;Farrage M. Khaleal,&nbsp;Mohammed Z. El-Bialy,&nbsp;Mohamed S. Kamar,&nbsp;Mokhles K. Azer,&nbsp;Mohamed M. Omar,&nbsp;Mohamed N. El Dawy,&nbsp;Ahmed Abdelaal,&nbsp;El Saeed R. Lasheen","doi":"10.1007/s11631-024-00698-y","DOIUrl":"10.1007/s11631-024-00698-y","url":null,"abstract":"<div><p>Beryl is the commercial source of beryllium and several varieties of it are valued as a gemstone. To contribute to understanding the mechanism of beryl formation, we carried out detailed geological, petrographical, and geochemical investigations on beryl mineralization occurrences in the Zabara-Wadi El Gemal (Z-WG) region. This region is an NW–SE trending tract that includes six beryl-hosting areas. The green gem variety of beryl (emerald) is restricted to phlogopite schist, pegmatite, and quartz veins. Prismatic hexagonal emerald crystals are well-developed in phlogopite schist and pegmatite. The gem variety emerald examined is sodic and Cr-dominant. It contains high concentrations of chromophore transition elements ordering Cr (up to 1511 ppm) &gt; V (up to 242 ppm) &gt; Sc (up to 245 ppm), giving rise to its vivid green color, reflecting mafic–ultramafic source contribution. Among the investigated emeralds, the Sikait area contains the highest BeO (av. 10.76wt.%) concentration. The compositional variability of emeralds is most likely attributed to the contribution from the host rocks. This is revealed by the examined emerald mineralization, for instance; the Abu Rusheid area (one of the best areas exposing rare metal-bearing granitoids) possesses the highest average of trace and REEs concentrations. In contrast, Um Kabu emerald has the highest contents of Co (av. 20 ppm), Ni (av. 299 ppm), MgO (av. 8.2wt.%), Fe₂O₃ (av. 3.12wt.%), and CaO (avg. 3.4wt.%) relative to other areas, which may be linked to contribution of ultramafic rocks exposed there. The proposed mechanism we suggest for emerald genesis is metasomatic interaction between felsic (intrusions, that are enriched with K, Na, Be, Li, and B, with mafic–ultramafic rocks that are enriched in Cr, V, Mg, Fe, and Ca. This interaction is marked by the formation of phlogopite schist, the growth of emerald crystals, and desilicated pegmatite.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"43 6","pages":"1105 - 1122"},"PeriodicalIF":1.4,"publicationDate":"2024-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141014214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Harnessing machine learning tools for water quality assessment in the Kebili shallow aquifers, Southwestern Tunisia","authors":"Zohra Kraiem,&nbsp;Kamel Zouari,&nbsp;Rim Trabelsi","doi":"10.1007/s11631-024-00689-z","DOIUrl":"10.1007/s11631-024-00689-z","url":null,"abstract":"<div><p>An integrated method that implements multivariate statistical analysis and ML methods to evaluate groundwater quality of the shallow aquifers of the Djerid and Kebili district, Southern Tunisia, was adopted. An evaluation of their suitability for irrigation and/or drinking purposes is necessary. A comprehensive hydrochemical assessment of 52 samples with entropy weighted water quality index (EWQI) was also proposed. Eleven water parameters were calculated to ascertain the potential use of those resources in irrigation and drinking. Multivariate analysis showed two main components with Dim1 (variance = 62.3%) and Dim.2 (variance = 22%), due to the bicarbonate, dissolution, and evaporation and the intrusion of drainage water. The evaluation of water quality has been carried out using EWQI model. The calculated EWQI for the Djerid and Kebili waters (i.e., 52 samples) varied between 7.5 and 152.62, indicating a range of 145.12. A mean of 79.12 was lower than the median (88.47). From the calculation of EWQI, only 14 samples are not suitable for irrigation because of their poor to extremely poor quality (26.92%). The bivariate plot showed high correlation for EWQI ~ TH (r = 0.93), EWQI ~ SAR(r = 0.87), indicating that water quality depended on those parameters. Different ML algorithms were successfully applied for the water quality classification. Our results indicated high prediction accuracy (SVM &gt; LDA &gt; ANN &gt; kNN) and perfect classification for kNN, LDA and Naive Bayes. For the purposes of developing the prediction models, the dataset was divided into two groups: training (80%) and testing (20%). To evaluate the models’ performance, RMSE, MSE, MAE and R² metrics were used. kNN (R² = 0.9359, MAE = 6.49, MSE = 79.00) and LDA (accuracy = 97.56%; kappa = 96.21%) achieved high accuracy. Moreover, linear regression indicated high correlation for both training (R² = 0.9727) and testing data (0.9890). This well confirmed the validity of LDA algorithm in predicting water quality. Cross validation showed a high accuracy (92.31%), high sensitivity (89.47%) and high specificity (95%). These findings are fundamentally important for an integrated water resource management in a larger context of sustainable development of the Kebili district.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"43 6","pages":"1065 - 1086"},"PeriodicalIF":1.4,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142664463","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hydrothermal alteration of the surface volcanic rocks at the Acoculco geothermal field, Mexico: a multi-parametric approach","authors":"America Yosiris García-Soto,&nbsp;Kailasa Pandarinath,&nbsp;E. Santoyo,&nbsp;Eduardo Gonzalez-Partida","doi":"10.1007/s11631-024-00683-5","DOIUrl":"10.1007/s11631-024-00683-5","url":null,"abstract":"<div><p>The studies on hydrothermal alteration-induced effects in surface and subsurface rocks provide useful information in the characterization and exploitation of a geothermal reservoir. Generally, these studies are based on traditional, and reliable methods like petrography (primary and secondary minerals, and grade of alteration), and geochemistry (mobility of elements, changes in mass and concentration of elements, and fluid inclusions). Recently, apart from these established methods, some methods based on the geochemical (Chemical Index of Alteration, CIA; Weathering Index of Parkar, WIP; Loss on Ignition, LOI; and Sulfur, S) and rock magnetic properties (magnetic susceptibility, χlf; and percentage frequency-dependent susceptibility, χfd%) are also being applied in the identification of whether a rock is an altered or a fresh one. The Acoculco Geothermal Field (AGF), Mexico, is characterized by high temperature and very low permeability, and it is considered a promissory Enhanced Geothermal System. The following changes are observed in the rocks as a result of an increase in hydrothermal alteration: (1) an increase in CIA, LOI, and S values, and a decrease in WIP; (2) an increase in quartz and quartz polymorph minerals (silicification), and clay minerals (argillization); and (3) decrease in χlf values. At AGF, the most altered surface acid rocks are characterized by entirely quartz and its polymorphs, and clay minerals. The present study also indicates the applicability of the binary plots of major elements (felsic vs mafic component) and rock magnetic parameters (χlf vs. χfd%). The rock with χfd% value of 2–10 and χlf value &lt; 0.5 × 10^–6 m³ kg⁻¹ indicate the presence of single domain and stable single domain grains, which in turn suggests that it is an altered rock. These methods are simple to apply, rapid, reliable, and have the potential to become effective tools for the identification of hydrothermally altered rocks during the initial stage of geothermal exploration.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"43 6","pages":"1037 - 1053"},"PeriodicalIF":1.4,"publicationDate":"2024-04-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11631-024-00683-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140731318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Zircon U–Pb geochronologic, geochemical and Sr–Nd–Pb isotope characteristics of the Beidaban granites in the North Qilian Orogenic Belt: Petrogenesis and tectonic implications","authors":"Tao Yang,&nbsp;Zhi-yuan Sun,&nbsp;Ming-liang Wang,&nbsp;Xiao-qiang Zhu,&nbsp;Jing-yu Zhao","doi":"10.1007/s11631-024-00684-4","DOIUrl":"10.1007/s11631-024-00684-4","url":null,"abstract":"<div><p>The tectonic evolution and crustal accretion process of the North Qilian Orogenic Belt (NQOB) are still under debate because of a lack of integrated constraints, especially the identification of the tectonic transition from arc to initial collision. Here we present results from zircon U–Pb geochronology, whole-rock geochemistry, and Sr–Nd–Pb isotope geochemistry of the Beidaban granites to provide crucial information for geodynamic evolution of NQOB. Zircon U–Pb dating yields an age of 468 ± 10 Ma for the Beidaban granites and most of the Beidaban samples contain amphibole, are potassium-rich, and have A/CNK values ranging from 0.7 to 0.9, illustrating that the Middle Ordovician Beidaban granites are K-rich, metaluminous, calc-alkaline granitoid. The geochemical characteristics indicate that the Beidaban granites are transitional I/S-type granitoids that formed in an arc setting. The isotopic compositions of initial (⁸⁷Sr/⁸⁶Sr)_i values ranging from 0.70545 to 0.71082 (0.70842 on average) and εNd(t) values ranging from − 10.9 to − 6.7 (− 8.8 on average) with two-stage Nd model ages (T_DM2) of 1.74–2.08 Ga suggest that the Beidaban granites originated from Paleoproterozoic crustal materials. In addition, the initial Pb isotopic compositions (²⁰⁶Pb/²⁰⁴Pb = 19.14–20.26; ²⁰⁷Pb/²⁰⁴Pb = 15.71–15.77; ²⁰⁸Pb/²⁰⁴Pb = 37.70–38.26) and geochemical features, such as high Th/Ta (17.43–30.12) and Rb/Nb (6.01–15.49) values, suggest that the Beidaban granite magma source involved recycled crustal components with igneous rocks. Based on these results in combination with previously published geochronological and geochemical data from other early Paleozoic igneous rocks, we suggest that the timing of the tectonic transition from arc to the initial collision to the final closure of the North Qilian Ocean can be constrained to the Middle-Late Ordovician (ca. 468–450 Ma).</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"43 6","pages":"1087 - 1104"},"PeriodicalIF":1.4,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140736370","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Design and application of the method for isolating magnetotactic bacteria","authors":"Xiao Zhijie,&nbsp;Lian Bin,&nbsp;Chen Jun,&nbsp;H. Henry Teng","doi":"10.1007/s11631-007-0252-y","DOIUrl":"10.1007/s11631-007-0252-y","url":null,"abstract":"<div><p>A simple apparatus was designed to effectively isolate magnetotactic bacteria from soils or sediments based on their magnetotaxis. Through a series of processes including sample incubation, MTB harvesting, isolation, purification and identification, several strains of bacteria were isolated from the samples successfully. By Transmission Electron Microscopy (TEM) and Energy-Dispersive X-ray Analysis (EDXA), these bacteria were certificated to be magnetotactic bacteria. The phylogenetic relationship between the isolated magnetic strains and some known magnetotactic bacteria was inferred by the construction of phylogenetic tree based on 16SrDNA sequences. This apparatus has been proven to have the advantages of being inexpensive, simple to assemble, easy to perform and highly efficient to isolate novel magnetotactic bacteria. The research indicated that the combined approach of harvesting MTB by home-made apparatus and the method of plate colony isolation could purify and isolate magnetotactic bacteria effectively.</p></div>","PeriodicalId":7151,"journal":{"name":"Acta Geochimica","volume":"26 3","pages":"252 - 258"},"PeriodicalIF":0.0,"publicationDate":"2007-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1007/s11631-007-0252-y","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"37831572","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}