Chemie Der Erde-Geochemistry最新文献

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Positive Matrix Factorization (PMF) based on geochemical data for revising geological map in semi-desert covered terrains: A case study from a map sheer of Urat Rear Banner, Inner Mongolia, China 基于地球化学数据的正矩阵分解(PMF)方法在半荒漠覆盖地区修正地质图——以内蒙古乌拉特后旗地图为例
IF 2.6 3区 地球科学
Chemie Der Erde-Geochemistry Pub Date : 2025-05-03 DOI: 10.1016/j.chemer.2025.126299
Yanling Sun, Xueqiu Wang, Hanliang Liu, Jian Zhou, Mingjun Xie
{"title":"Positive Matrix Factorization (PMF) based on geochemical data for revising geological map in semi-desert covered terrains: A case study from a map sheer of Urat Rear Banner, Inner Mongolia, China","authors":"Yanling Sun,&nbsp;Xueqiu Wang,&nbsp;Hanliang Liu,&nbsp;Jian Zhou,&nbsp;Mingjun Xie","doi":"10.1016/j.chemer.2025.126299","DOIUrl":"10.1016/j.chemer.2025.126299","url":null,"abstract":"<div><div>There is a significant deficiency for geological mapping in the Gobi Desert terrain covered by wind-blown sands with limited exposure of bedrock. Major and minor element data of stream sediments using Positive Matrix Factorization (PMF) analysis were employed to interpret the geological signatures from the Urat Rear Banner, a representative area of the Gobi Desert terrains. Six primary geochemical factors (M1, M2, M3, T1, T2, T3), corresponding to geological units were extracted from 8 major elements and 18 minor elements. Notably, the SiO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub>-K<sub>2</sub>O-and Pb-Ba-Th-Be-Y-Li-U combinations (primarily M1 and T1) are associated with felsic intrusive rocks, complex metamorphic rocks, and sandstones. The MgO-Fe<sub>2</sub>O<sub>3</sub>-TiO<sub>2</sub>, Cu-Mn-Zn-Co combinations (primarily M2 and T2) indicate basic intrusive rocks, complexes. The Al<sub>2</sub>O<sub>3</sub>-Na<sub>2</sub>O-CaO, Sr-Co-Mn-P-Cu-Zn-Ba (primarily M3 and T3) are related to neutral intrusive bodies (or complexes) and marble (or limestone). Additionally, the study utilizes standardized M1, M2, and M3 factor scores to refine the delineation of lithological boundaries of magmatic rocks. The findings highlight the effectiveness of the PMF method coupled with stream sediment geochemistry, as a powerful tool for extracting geological signatures. This approach offers valuable insights into geological information extraction in Gobi Desert terrains, particularly for identifying and delineating lithological boundaries within magmatic rock formations.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 3","pages":"Article 126299"},"PeriodicalIF":2.6,"publicationDate":"2025-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143911632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Anticlockwise metamorphic evolution of the Tin Hallen area (Ahnet Terrane, NW Hoggar, Algeria): Evidence for granulitic and blueschist-facies metamorphism in Fe-Ti metagabbros 阿尔及利亚NW Hoggar Ahnet地块Tin Hallen地区的逆时针变质演化:铁-钛变质岩中粒状和蓝片岩相变质的证据
IF 2.6 3区 地球科学
Chemie Der Erde-Geochemistry Pub Date : 2025-05-01 DOI: 10.1016/j.chemer.2024.126245
Malika Mokri , Khadidja Ouzegane , Sid Ali Doukkari , Saida Ait Djafer , Jean-Robert Kienast , Zouhir Adjerid , Nadia Boureghda , Hamid Haddoum
{"title":"Anticlockwise metamorphic evolution of the Tin Hallen area (Ahnet Terrane, NW Hoggar, Algeria): Evidence for granulitic and blueschist-facies metamorphism in Fe-Ti metagabbros","authors":"Malika Mokri ,&nbsp;Khadidja Ouzegane ,&nbsp;Sid Ali Doukkari ,&nbsp;Saida Ait Djafer ,&nbsp;Jean-Robert Kienast ,&nbsp;Zouhir Adjerid ,&nbsp;Nadia Boureghda ,&nbsp;Hamid Haddoum","doi":"10.1016/j.chemer.2024.126245","DOIUrl":"10.1016/j.chemer.2024.126245","url":null,"abstract":"<div><div>The Tin Hallen area (Ahnet terrane, NW Hoggar, Algeria) represents one of the most well-preserved examples of blueschist-facies metamorphism in West Gondwana, associated with Fe<img>Ti garnet-bearing metagabbros. The textural analysis reveals four distinct stages. The first stage (M1) is magmatic, characterized by an orthopyroxene, plagioclase ± clinopyroxene, and ilmenite assemblage, primarily observed in areas distant from shear zones. The second stage (M2) involves the development of granulite-facies coronae and symplectites composed of garnet, clinopyroxene2, quartz, rutile, and brown amphibole. The third stage (M3) is defined by the appearance of green amphibole, sphene and epidote. Finally, the fourth stage (M4) is marked by the formation of glaucophane-bearing schists, indicating an advanced retrograde evolution within shear zones. Through the integration of thermodynamic modeling (P-T-M<sub>H2O</sub> pseudosections), petrology, mineral chemistry, and reaction textures, a counterclockwise P-T path has been established for the area. The Tin Hallen metagabbros display a prominent granulitic imprint surrounding magmatic relicts in H<sub>2</sub>O-undersaturated conditions. This evolution reflects a pressure increase at nearly constant temperature, progressing from c. 6 kbar and c. 900 °C (M1) to 9–10.5 kbar and 850–900 °C (M2), likely linked to the thickening of the magmatic arc root, as suggested by other international studies. The granulitization is followed by further pressure increases and temperature decreases, leading to the mylonitic garnet amphibolite stage (M3) at ~14 kbar and 740 °C, along with a significant rise in M<sub>H2O</sub>. Moreover, the presence of an original blueschist-facies stage (M4) with high-pressure, low-temperature (HP-LT) conditions (c. 8 kbar and 470 °C) is characteristic of cold subduction gradients (10–15 °C/km).</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 2","pages":"Article 126245"},"PeriodicalIF":2.6,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290640","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Tourmaline associated with orogenic gold occurrences in the Silet terrane, South Algeria: Evolution of composition and redox state during hydrothermal crystallization 阿尔及利亚南部Silet地体中与造山带金矿相关的电气石:热液结晶过程中组成和氧化还原状态的演化
IF 2.6 3区 地球科学
Chemie Der Erde-Geochemistry Pub Date : 2025-05-01 DOI: 10.1016/j.chemer.2025.126259
Ismahen Chaouche , Jan Cempírek , Mohamed Talbi , Riad Ben El Khaznadji , Nadjet Ait Taleb , Yves Fuchs
{"title":"Tourmaline associated with orogenic gold occurrences in the Silet terrane, South Algeria: Evolution of composition and redox state during hydrothermal crystallization","authors":"Ismahen Chaouche ,&nbsp;Jan Cempírek ,&nbsp;Mohamed Talbi ,&nbsp;Riad Ben El Khaznadji ,&nbsp;Nadjet Ait Taleb ,&nbsp;Yves Fuchs","doi":"10.1016/j.chemer.2025.126259","DOIUrl":"10.1016/j.chemer.2025.126259","url":null,"abstract":"<div><div>In the Silet terrane (western Hoggar, southern Algeria), gold occurs in association with tourmaline in quartz veins. In the Assouf Mellen, Seldrar, and Idreksi occurrences, gold-bearing veins cut diorite and granodiorite complexes of the pre-orogenic Tonalite-Trondhjemite-Granodiorite group (868–840 Ma). These veins trend dominantly in the N-S, NE-SW, and NW-SE directions, and are preferentially developed at the intersection zones of secondary NE-SW and NW-SE fault splays off the main 4°30′ fault zone (Iskel Shear Zone). Free gold is present as inclusions disseminated in quartz and tourmaline, and as fissure-fillings in deformed tourmaline crystals. Gold was also found as inclusions in chalcopyrite and in iron oxides.</div><div>Based on the mineral chemistry, the tourmaline belongs to the alkali group and represents the schorl–dravite and foitite–oxy-foitite series and shows evolution trends to bosiite/povondraite; tourmaline components from the calcic group (lucchesiite, magnesio-lucchesiite) are minor only. Tourmaline in Silet was likely formed as Al-deficient Fe<sup>3+</sup>-enriched schorl (Tur I), later recrystallized (Tur II) and enriched in Mg and Al with higher X-site vacancy (Mg-rich schorl to Fe-rich dravite). In the Seldrar occurrences (middle part of Silet terrane), gold is associated with tourmaline with high initial Fe<sup>3+</sup>-contents (Tur I) while the assemblage of the later Tur II is barren. The evolution towards Fe<sup>3+</sup>-rich schorl may be explained as a result of more oxidizing conditions in the late stage of formation of the mineralized quartz veins. Part of gold was remobilized by low-temperature weathering processes.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 2","pages":"Article 126259"},"PeriodicalIF":2.6,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290642","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Integrated remote sensing and geophysical studies of the Silet-Tin Felki area: Insights into the Pan-African tectonics and magmatic evolution of the Hoggar Shield, Southern Algeria Silet-Tin Felki地区的综合遥感和地球物理研究:阿尔及利亚南部Hoggar地盾泛非构造和岩浆演化的见解
IF 2.6 3区 地球科学
Chemie Der Erde-Geochemistry Pub Date : 2025-05-01 DOI: 10.1016/j.chemer.2024.126242
Narimene Berrahmane , Abderrahmane Bendaoud , El-Hocine Fettous , Sid Ali Doukkari , Takfarinas Lamri , Basem Zoheir , Mohamed Hamoudi
{"title":"Integrated remote sensing and geophysical studies of the Silet-Tin Felki area: Insights into the Pan-African tectonics and magmatic evolution of the Hoggar Shield, Southern Algeria","authors":"Narimene Berrahmane ,&nbsp;Abderrahmane Bendaoud ,&nbsp;El-Hocine Fettous ,&nbsp;Sid Ali Doukkari ,&nbsp;Takfarinas Lamri ,&nbsp;Basem Zoheir ,&nbsp;Mohamed Hamoudi","doi":"10.1016/j.chemer.2024.126242","DOIUrl":"10.1016/j.chemer.2024.126242","url":null,"abstract":"<div><div>The Silet-Tin Felki area, located within the Tuareg Shield, represents a key area for understanding the Pan-African orogeny and associated magmatic processes. This study employs a comprehensive approach, integrating remote sensing, airborne geophysics, and the previously available geochemical data to produce an enhanced lithological and structural map of the area. Remote sensing methods, including optimal RGB band combinations and principal component analysis (PCA), effectively distinguish between volcanic, granitoid, and metamorphic units. High-resolution magnetic and gamma-ray spectrometry further elucidate lithological boundaries and tectonic features, including significant shear zones. The study identifies two distinct lithological blocks, separated by the 4°50′E lithospheric shear zone: the LATEA-Aouilène block to the east, featuring Neoproterozoic high-grade metamorphic rocks, and the Pharusien Belt to the west, characterized by Neoproterozoic volcanic arc and accretionary wedge complexes. The Tonian TTG batholiths in the northern Silet region display moderate radioactivity and magnetic signatures, contrasting with the highly radiogenic post-orogenic granites.</div><div>Key geodynamic features, such as mafic-ultramafic intrusions associated with a back-arc basin, were delineated, refining the regional geological model and enhancing the understanding of magmatic evolution and tectonic interactions. The integration of gamma-ray spectrometry and aeromagnetic data enabled the detailed mapping of pre-, <em>syn</em>-, and post-collisional granitoids, including transitional TTG suites, and revealed complex tectonic history with significant shear zones and lineaments. This updated geological framework provides critical insights for future exploration and underscores the need for further geochronological and petrological research to fully comprehend the tectono-magmatic evolution of this part of the Tuareg Shield.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 2","pages":"Article 126242"},"PeriodicalIF":2.6,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290655","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Mineralogical and geochemical characteristics of AlFe granulites and banded iron formations in the Archean supracrustal unit of the In Ouzzal terrane (NW Hoggar, Algeria) 阿尔及利亚西北Hoggar in Ouzzal地块太古宙上地壳单元中AlFe麻粒岩和带状铁组的矿物学和地球化学特征
IF 2.6 3区 地球科学
Chemie Der Erde-Geochemistry Pub Date : 2025-05-01 DOI: 10.1016/j.chemer.2025.126261
Assia Badani , Saïda Aït Djafer , Zouhir Adjerid , Khadidja Ouzegane , Jean-Robert Kienast , Nadia Boureghda
{"title":"Mineralogical and geochemical characteristics of AlFe granulites and banded iron formations in the Archean supracrustal unit of the In Ouzzal terrane (NW Hoggar, Algeria)","authors":"Assia Badani ,&nbsp;Saïda Aït Djafer ,&nbsp;Zouhir Adjerid ,&nbsp;Khadidja Ouzegane ,&nbsp;Jean-Robert Kienast ,&nbsp;Nadia Boureghda","doi":"10.1016/j.chemer.2025.126261","DOIUrl":"10.1016/j.chemer.2025.126261","url":null,"abstract":"<div><div>In the northern In Ouzzal terrane, Al<img>Fe granulites and banded iron formations (BIFs) constitute a supracrustal unit, locally associated with Al<img>Mg granulites, marbles, calc-silicate granulites, and mafic or ultramafic rocks. The Al<img>Fe granulites display variable SiO<sub>2</sub> content (55.62 to 79.26 wt%) and X<sub>Mg</sub> ratio (0.11–0.48) and are characterised by spinel–quartz parageneses, locally retrograded to garnet-sillimanite coronas. Cordierite is absent in some Al<img>Fe granulite samples, while others contain cordierite-spinel or cordierite-spinel-orthopyroxene symplectites that are a breakdown product of spinel-garnet-sillimanite-quartz assemblages. The BIFs display a unique corundum-quartz-magnetite paragenesis, characteristic of ultra-high-temperature (UHT) metamorphic conditions. Another exceptionally rare type of BIF in the region consists of orthoferrosilite (X<sub>Mg</sub> = 0.14–0.29) in equilibrium with high chlorine-rich (3.88 to 5.12 wt%) hastingsite, surpassing values reported in international literature. The Al<img>Fe granulites exhibit geochemical characteristics comparable to post-Archean shales and are interpreted as the products of mixed protoliths. These protoliths consist of mature detrital material, primarily quartz, derived from trondhjemite and tonalite sources emplaced between 3300 and 2700 Ma. Additionally, they include immature predominantly chloritic components enriched in Al, Cr (100–300 ppm) and V (100–200 ppm). Banded iron formations (BIFs) are mainly composed of three key components: SiO₂, FeO, and Fe₂O₃, with their combined content ranging from 91.51 to 99.23 wt%. The concentrations of Al₂O₃, TiO₂, CaO, and rare earth elements (REEs) are notably low, consistent with those of classic Archean BIFs. This composition implies that their formation resulted from the direct precipitation of Fe-rich minerals in oxidizing marine exhalative environments, while silica-rich layers (mainly chert) formed during periods of low oxygen concentration, and with the absence of detrital materials.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 2","pages":"Article 126261"},"PeriodicalIF":2.6,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290772","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Formation of pseudotachylytes under granulite facies conditions in the UHT In Ouzzal terrane (Western Hoggar, Algeria): Witnesses of paleoseism in the Paleoproterozoic lower continental crust at 0.82 Ga Ouzzal地块(阿尔及利亚Hoggar西部)UHT麻粒岩相条件下伪岩的形成:0.82 Ga古元古代下大陆地壳古地震活动的见证
IF 2.6 3区 地球科学
Chemie Der Erde-Geochemistry Pub Date : 2025-05-01 DOI: 10.1016/j.chemer.2025.126253
E.-H. Fettous , Y. Mahdjoub , P. Monie
{"title":"Formation of pseudotachylytes under granulite facies conditions in the UHT In Ouzzal terrane (Western Hoggar, Algeria): Witnesses of paleoseism in the Paleoproterozoic lower continental crust at 0.82 Ga","authors":"E.-H. Fettous ,&nbsp;Y. Mahdjoub ,&nbsp;P. Monie","doi":"10.1016/j.chemer.2025.126253","DOIUrl":"10.1016/j.chemer.2025.126253","url":null,"abstract":"<div><div>Archaean charnockitic orthogneisses transected by 2.0 Ga high-grade exhumed ductile shear zones form part of the ultra-high temperature In Ouzzal Terrane, located in the western Hoggar, within the Neoproterozoic Pan-African Trans-Saharan belt of north-west Africa. Faults and injection veins of pseudotachylytes exhibit sharp contacts with their host charnockitic orthogneisses and are composed of a dark, and sometimes banded matrix, containing numerous clasts of pyroxene, feldspar, quartz, and rarely biotite. Recrystallized mineral assemblages in the matrix are indicative of granulitic facies conditions and consist of very fine-grained crystals of hypersthene, phlogopite, oligoclase, orthoclase, quartz, and accessory Mn-ilmenite and Cr-magnetite. This assemblage differs from that of the charnockitic orthogneiss host notably by the absence of the mesoperthitic K-feldspar. The chemical compositions of the pseudotachylytes are in general similar to those of the charnockitic orthogneisses suggesting a non-selective melting process consistent with in situ and total recrystallization. The chemical variations are observed in Tin Tchik Tchik pseudotachylytes and shear planes, including slight enrichments of calcium in orthopyroxene, plagioclase, and K-feldspar, as well as iron in biotite. These variations are attributed to recrystallization under decreasing temperature during faster cooling. The newly formed granulitic-facies mineral phases within the pseudotachylytes are synchronous with brittle deformation, lining fractures parallel to major shear zones and occupying spaces created by T-fractures, or those between Riedel R and T fractures, or P and R'. This Riedel fracture network indicates NW-SE to WNW-ESE shortening.</div><div>The <sup>40</sup>Ar/<sup>39</sup>Ar dating of the pseudotachylyte matrix indicates its formation at 820.5 ± 6.6 Ma, providing the first evidence of early Neoproterozoic tectonism in the In Ouzzal terrane. Regionally, this event corresponds to the convergence period between the West African Craton and East Saharan Craton leading to subduction and the development of oceanic/continental arcs in western Hoggar. Earlier polyphase dehydration of charnockitic orthogneiss, during Archaean partial melting events (2.65 and 2.5 Ga) and Eburnean (2.0 Ga) ultra-high temperature metamorphism, suggests a reactivation under brittle coseismic conditions of Paleoproterozoic ductile main shear zones at 0.82 Ga in a nearly anhydrous lower crust and provides a natural example of earthquakes in the lower continental crust, controlled by a brittle rheology.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 2","pages":"Article 126253"},"PeriodicalIF":2.6,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Evidence of an Archean-Paleoproterozoic micro-continent remobilized during the Neoproterozoic from the western Hoggar (Tuareg Shield, Algeria): Geodynamic evolution and implication on gold mineralization 阿尔及利亚Hoggar (Tuareg盾)西部新元古代再活动的太古宙-古元古代微大陆的证据:地球动力学演化及其金矿化意义
IF 2.6 3区 地球科学
Chemie Der Erde-Geochemistry Pub Date : 2025-05-01 DOI: 10.1016/j.chemer.2024.126213
Abderrahmane Bendaoud , Renaud Caby , Safouane Djemaï , Olivier Bruguier , Djamal-Eddine Aissa , Aboubakr Deramchi , Sid Ali Doukkari , Khadidja Ouzegane , Fatna Kourim , Jean-Robert Kienast
{"title":"Evidence of an Archean-Paleoproterozoic micro-continent remobilized during the Neoproterozoic from the western Hoggar (Tuareg Shield, Algeria): Geodynamic evolution and implication on gold mineralization","authors":"Abderrahmane Bendaoud ,&nbsp;Renaud Caby ,&nbsp;Safouane Djemaï ,&nbsp;Olivier Bruguier ,&nbsp;Djamal-Eddine Aissa ,&nbsp;Aboubakr Deramchi ,&nbsp;Sid Ali Doukkari ,&nbsp;Khadidja Ouzegane ,&nbsp;Fatna Kourim ,&nbsp;Jean-Robert Kienast","doi":"10.1016/j.chemer.2024.126213","DOIUrl":"10.1016/j.chemer.2024.126213","url":null,"abstract":"<div><div>The western boundary of the Tirek terrane in the Hoggar contains the two largest gold deposits in Algeria, namely the Amesmessa and Tirek gold fields. New geological mapping of this area and results of a combined petrological, geochemical and geochronological study (U-Pb zircon geochronological (LA-)ICP-MS method) reveals a Paleoproterozoic TTG basement, dated at 1965 ± 18 Ma (inherited zircons from 2771 to 2006 Ma), overlain by a supracrustal unit made up of quartzites and metapelites. Detrital zircons from metapelites yielded ages ranging from Archaean to Paleoproterozoic (2710 Ma–2050 Ma). Furthermore, sills and dykes of sub-alkaline orthogneisses that intrude the previous lithologies have been dated at 1843 ± 19 Ma. On the other hand, the migmatitic granitic-granodioritic batholith, which covers 50 % of the studied area and intrudes all units, has a subduction magmatism affinity and is dated at 663 ± 4 Ma.</div><div>The study area was affected by a HT-LP metamorphic overprint during a clockwise P-T evolution with a peak conditions around 800–850 °C at 5 kbar followed by a decompression, then a cooling reaching the P-T conditions of 600 °C and 3 kbar. Uranium-Pb dating of monazite yields an age of 578 ± 5 Ma, which is interpreted to reflect the time of peak metamorphic overprint synchronous with the emplacement of synkinematic granites along shear zones with transcurrent movement. During this event, the western border of the studied area, the East Ouzzalian Shear zone, was the site of magmatic intrusions as well as the circulation of various fluids. This promoted an important fluid/rock interaction event, leading to extraction of gold by fluid percolation through the rocks and its deposition along N-S/NE-SW quartz vein ore shoots. The comparison with the western terranes of the Tuareg Shield (In Ouzzal, Iforas, Tassendjanet, and Kidal terranes) suggests that Tirek and these terranes represent relics of a single Archean-Paleoproterozoic continent. Currently, the Archean lower crust cross out in the central part of this micro-continent. The latter is mainly affected by Paleoproterozoic granulite facies metamorphism, unlike the Paleoproterozoic middle crust, which is exposed on either side and was strongly remobilized during the Pan-African orogeny (850–570 Ma), allowing gold mineralization during the later stages of this event.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 2","pages":"Article 126213"},"PeriodicalIF":2.6,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290641","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Reactions in UHT calc-silicate granulites from the In Ouzzal terrane (Western Hoggar, South Algeria): Implication for pressure-temperature-fluid evolution In Ouzzal Terrane(阿尔及利亚南部西霍加尔)超高温钙硅酸盐花岗岩中的反应:对压力-温度-流体演化的影响
IF 2.6 3区 地球科学
Chemie Der Erde-Geochemistry Pub Date : 2025-05-01 DOI: 10.1016/j.chemer.2024.126079
Nadia Boureghda , Khadidja Ouzegane , Saïda Aït-Djafer , Jean-Robert Kienast , Abderrahmane Bendaoud , Amar Arab , Zouhir Adjerid
{"title":"Reactions in UHT calc-silicate granulites from the In Ouzzal terrane (Western Hoggar, South Algeria): Implication for pressure-temperature-fluid evolution","authors":"Nadia Boureghda ,&nbsp;Khadidja Ouzegane ,&nbsp;Saïda Aït-Djafer ,&nbsp;Jean-Robert Kienast ,&nbsp;Abderrahmane Bendaoud ,&nbsp;Amar Arab ,&nbsp;Zouhir Adjerid","doi":"10.1016/j.chemer.2024.126079","DOIUrl":"10.1016/j.chemer.2024.126079","url":null,"abstract":"<div><div><span>Calc-silicate granulites<span> constitute a relatively small part of the whole granulitic material outcrops characterizing the In Ouzzal terrane (NW Hoggar, South Algeria). However, these rocks preserve a number of spectacular reaction textures that could be effectively used to infer their pressure-temperature-fluid history. These textures are interpreted using P-T and T-X</span></span><sub>CO2</sub> grids in the simplified CaO-Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub><span>-Vapor system. In this process, sequences of reactions have been subdivided into two distinct stages: (i) the early prograde stage that was accompanied by significant rise of temperature from about 800 °C up to 1050 °C at around10 kbar followed by (ii) the decompression stage from about 9 to 6 kbar. During the prograde stage, coarse grained wollastonites were produced according to the reaction calcite<span> + quartz → wollastonite + CO</span></span><sub>2</sub><span>. Furthermore, in the peak pressure temperature stage, the reaction producing wollastonite + scapolite<span> from coarse primary garnet consumes CO</span></span><sub>2</sub> with temperature increasing from 850 °C to 1000 °C according to the reaction 3grossular + 3CO<sub>2</sub> → 3wollastonite + 2calcite + scapolite. The latest reactions have been occurred during the decompression stage from about 10 kbar to 5 kbar and cooling from 1000 °C to 800 °C. The growth of calcite + quartz around wollastonite besides to garnet coronas between wollastonite, calcite and scapolite are explained by the reaction: calcite + quartz → wollastonite + CO<sub>2</sub> and 3wollastonite + scapolite +2calcite → 3grossular + 3CO<sub>2</sub>. The appearance of anorthite around scapolite occurs following a decrease of temperature independently to the fluids according to the reaction scapolite → 3anorthite + calcite. All reactions took place at CO<sub>2</sub> low pressure which was estimated between 0.04 and 0.55.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 2","pages":"Article 126079"},"PeriodicalIF":2.6,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139469519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Pan-African eclogite-facies tectonic mélange in the Egéré area, Tuareg Shield (Algeria): Integrated approaches for lithological and structural mapping 图阿雷格盾(阿尔及利亚)eg<s:1>区域泛非榴辉岩相构造剖面:岩性和构造制图的综合方法
IF 2.6 3区 地球科学
Chemie Der Erde-Geochemistry Pub Date : 2025-05-01 DOI: 10.1016/j.chemer.2024.126217
Yasser Laichaoui , Mohamed Hamoudi , Khadidja Ouzegane , Jean-Paul Liégeois , Walid Farhi , Takfarinas Lamri , Sidali Doukkari , Alain Vauchez , Amar Arab , Massinissa Amara
{"title":"Pan-African eclogite-facies tectonic mélange in the Egéré area, Tuareg Shield (Algeria): Integrated approaches for lithological and structural mapping","authors":"Yasser Laichaoui ,&nbsp;Mohamed Hamoudi ,&nbsp;Khadidja Ouzegane ,&nbsp;Jean-Paul Liégeois ,&nbsp;Walid Farhi ,&nbsp;Takfarinas Lamri ,&nbsp;Sidali Doukkari ,&nbsp;Alain Vauchez ,&nbsp;Amar Arab ,&nbsp;Massinissa Amara","doi":"10.1016/j.chemer.2024.126217","DOIUrl":"10.1016/j.chemer.2024.126217","url":null,"abstract":"<div><div>The Tuareg Shield is made up of 25 terranes separated by extensive shear zones that are several hundred km-long, which have been attributed to a northward post-collisional tectonic escape during the Pan-African orogeny. The development of these shear zones was accompanied by abundant high-K calc-alkaline batholiths and plutons (~630–580 Ma). In the northern Egéré-Aleksod terrane of Central Hoggar (LATEA metacraton), the Egéré area exhibits minimal Pan-African magmatism, preserving earlier tectonic events such as subduction, collision, and terrane exhumation. The Egéré region consists of a parautochthonous amphibolite-facies unit (Arechchoum Group) and three eclogite-facies nappe units (Lower Egéré, Upper Egéré, and Oneral groups). These were thrust over the Archean Amadror cratonic core after the subduction of the LATEA passive margin superstructure to which they belong. These units have Paleoproterozoic protoliths, predominantly magmatic in the Arechchoum Group, or mixed magmatic and sedimentary in the Egéré Group, while the Oneral Group, which forms the uppermost nappe, comprise Neoproterozoic sediments.</div><div>Space-borne imagery data are used to map the eclogitic layers, integrated with magnetic and gravity surveys to delineate major shear and thrust zones. In addition, 2D modelling of magnetic and gravity data was used to investigate the upper crust, revealing a Pan-African granitic batholith and a large ultramafic-mafic bod at depth. The results allowed detailed geological mapping of such a complex tectonic mélange belonging to both lower and upper plate segments. Integrated with the published geochronological data, this mélange includes rocks with Rhyacian to Statherian, Calymmian, and Early Cryogenian ages, all of which underwent Late Cryogenian high-pressure metamorphism, followed by Ediacaran high-temperature metamorphism and tectonic escape processes.</div><div>Our results reveal the complex tectonic evolution of a former passive margin that was subducted to great depths during the Pan-African orogeny. The preservation of early subduction and exhumation events provides key insights into tectonometamorphic processes and deep crustal evolution in this high-pressure metamorphic terrane.</div></div>","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 2","pages":"Article 126217"},"PeriodicalIF":2.6,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290656","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Geochemical comparison of biotite from TTG batholiths and A-type complexes on either side of the Tin-Dahar fault: Geodynamic considerations (Silet region, Western Hoggar, Algeria) Tin-Dahar断裂两侧TTG基岩和a型杂岩中黑云母的地球化学比较:地球动力学的考虑(阿尔及利亚西霍格尔Silet地区)
IF 2.6 3区 地球科学
Chemie Der Erde-Geochemistry Pub Date : 2025-05-01 DOI: 10.1016/j.chemer.2025.126269
Sarra Mokaddem , Fatene Bechiri-Benmerzoug , Hamid Bechiri , Halima Chaa , Latifa Remki , Rekia Kheloui , Yousra Kara , Sara Miloudi , Khadidja Bouzid , Nicolas Rividi , Bernard Bonin
{"title":"Geochemical comparison of biotite from TTG batholiths and A-type complexes on either side of the Tin-Dahar fault: Geodynamic considerations (Silet region, Western Hoggar, Algeria)","authors":"Sarra Mokaddem ,&nbsp;Fatene Bechiri-Benmerzoug ,&nbsp;Hamid Bechiri ,&nbsp;Halima Chaa ,&nbsp;Latifa Remki ,&nbsp;Rekia Kheloui ,&nbsp;Yousra Kara ,&nbsp;Sara Miloudi ,&nbsp;Khadidja Bouzid ,&nbsp;Nicolas Rividi ,&nbsp;Bernard Bonin","doi":"10.1016/j.chemer.2025.126269","DOIUrl":"10.1016/j.chemer.2025.126269","url":null,"abstract":"&lt;div&gt;&lt;div&gt;We studied the chemical composition of primary biotite (n = 265 chemical analyses, performed by electron microprobe) from some acidic plutonic rocks in the central part of the Silet terrane (Hoggar, Algeria). Which is considered an island arc accreted onto the metacraton LATEA during the climax of the Pan-African orogeny at around 650 Ma, accompanied by northward migration of LATEA, following final clamping between the West African craton and the Saharan metacraton. The plutonic acidic rocks constitute nearly 70 % from study area, essentially represented by Tonian-Cryogenian TTG batholiths and Ediacaran-Fortunian A-type granitic complexes. They cross-cut Neoproterozoic volcano-sedimentary series and are organized into two narrow stripes with opposite isotopic signatures, separated by the N-S Tin-Dahar fault: the Juvenile Western Stripe (J-WS) and the Contaminated Eastern Stripe (C-ES). We compared biotite of the western stripe (TTG + type A granitic batholiths) with that of the same rocks of the eastern stripe (C-ES). So, we selected three TTG batholiths (Tin-Tekadiouit, Ahambatou and Silet) + two A-type granite complexes (Tin-Erit and Tioueïne) from the J-WS and one TTG type (Eheli) + two A-type granite (Teg-Orak and Inedjaren) from the C-ES. The petrographic observation shows in all studied rocks of the western stripe (J-WS) that biotite is often associated with amphibole, whereas in the eastern stripe rocks (C-ES), biotite is only. Consequently, biotite from both TTG and A-type granitoids from J-WS differ in chemical compositions from biotite from C-ES. Three biotite types were determined in the studied felsic rocks: 1- Mg-biotite in TTG batholiths of the two stripes (Tin-Tekadiouit, Ahambatou, Silet and Eheli) and in the A-type granite complex of Inedjaren, located in the C-ES; 2- Fe-biotite–annite of A-type Tioueine and Tin-Erit complexes (J-WS) and 3- Fe-biotite–siderophyllite of A-type Teg-Orak (C-ES). In detail, Mg-biotite in TTG of the J-WS reflects calc-alkaline, orogenic and peraluminous host rocks, whereas, in the Eheli TTG and the Inedjaren A-type of C-ES, it reflects calc-alkaline, orogenic host rocks. Fe-biotite–annite of the A-type granite of J-WS reflects alkali-calcic to alkaline anorogenic host rocks when Fe-biotite–siderophyllite from Teg-Orak complex, located to the north of C-ES, reflects calc-alkaline to alkali-calcic rocks.&lt;/div&gt;&lt;div&gt;Crystallization temperatures and pressures of Mg-biotite in TTG batholiths of J-WS are lower (750–800 °C, 3–6 kbar) than those recorded in the Eheli TTG batholith (850–900 °C, 4–8 kbar) of C-ES. Mg-biotite of the Inedjaren A-type complex (800–900 °C, 3–6 kbar) of C-ES shows higher temperature than biotite of the other A-type complexes (Fe-biotite–annite trend; Fe-biotite–siderophyllite trend), yielding variable pressure values (700–750 °C, 3–10 kbar).&lt;/div&gt;&lt;div&gt;The three different types of biotite are emphasized by estimates of thermodynamic conditions (T, P, &lt;em&gt;f&lt;/em&gt;O&lt;sub&gt;2&lt;/sub&gt;)","PeriodicalId":55973,"journal":{"name":"Chemie Der Erde-Geochemistry","volume":"85 2","pages":"Article 126269"},"PeriodicalIF":2.6,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144290639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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