Lithos最新文献

{"title":"Petrogenesis of early Paleozoic syn-collisional granitoids and enclaves in Western Kunlun, Northwest China: Implications for the growth of continental crust","authors":"Yu Zhang ,&nbsp;Qichao Zhang ,&nbsp;Xin Wang","doi":"10.1016/j.lithos.2024.107844","DOIUrl":"10.1016/j.lithos.2024.107844","url":null,"abstract":"<div><div>The Western Kunlun Orogenic Belt (WKOB), along the northwestern margin of the Qinghai–Xizang Plateau, was formed by the collision of Gondwana-derived terranes to the south and the Tarim Block to the north and was closely associated with closure of the Proto-Tethys Ocean during the late Neoproterozoic to early Paleozoic. We present a combined zircon U<img>Pb geochronology, whole-rock composition, and Sr–Nd–Hf isotopic study of syn-collisional granitoid plutons and mafic microgranular enclaves (MMEs) in the region. Zircon U<img>Pb dating yields ages of 443.8 ± 4.4, 451.9 ± 4.2, 462.9 ± 3.5, and 456 ± 4.2 Ma for the Tongayoupuagezi, Shanjie, and Pishigai plutons and MMEs from the Pishigai pluton, respectively. The granitoids are metaluminous to weakly peraluminous (A/CNK = 1.00–1.17) and belong to the high-K calc-alkaline series. They have (⁸⁷Sr/⁸⁶Sr)_i ratios of 0.7058–0.7154, ε_Nd(t) values of −8.78 to −0.93, and ε_Hf(t) values of −19.72 to +6.87. The MMEs have variable SiO₂ contents (45.7–60.2 wt%) and are more mafic than the host granitoids, but have similar Sr–Nd–Hf isotopic compositions to the host granitoids [(⁸⁷Sr/⁸⁶Sr)_<em>i</em> = 0.7102–0.7110; ε_Nd(t) = −6.57 to −3.56; ε_Hf(t) = −7.17 to −1.81]. The MMEs are fragments of cumulates formed during the early stages of magma evolution. The granitoids were produced by the partial melting of a mélange source. The new data support the view that the Middle–Late Ordovician syn-collisional granitoids with MMEs distributed along the WKOB represent a magmatic response to terrane collision. This suggests that juvenile crustal growth in older orogenic systems, which occurs by arc addition, also involves some vertical addition during the final stage of orogenic collision. Our study suggests that mélange diaper melting is a key mechanism of crustal growth during the syn-collision stage in continental collision zones, associated with slab breakoff.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107844"},"PeriodicalIF":2.9,"publicationDate":"2024-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142551922","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis and high-precision U-Pb zircon geochronology of the Howley Islands intrusions, Central Newfoundland Appalachians: Hydrous magmatism of Emsian age (ca. 400 Ma) along a multi-million-ounce orogenic gold belt","authors":"I.W. Honsberger ,&nbsp;H.A.I. Sandeman ,&nbsp;S.L. Kamo ,&nbsp;W. Bleeker","doi":"10.1016/j.lithos.2024.107837","DOIUrl":"10.1016/j.lithos.2024.107837","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The Howley Islands intrusions consist of three coarse-grained amphibole-phlogopite/biotite quartz gabbro dykes and one medium-grained amphibole-biotite quartz diorite body that cut rocks of the Exploits Subzone in central Newfoundland along strike from the multi-million-ounce Valentine gold deposits. The petrogeneses and ages of these rocks were investigated to better constrain the process evolution of the orogenic gold belt that extends for more than 200 km across central Newfoundland.&lt;/div&gt;&lt;div&gt;The quartz gabbro dykes are composed of magnesio-ferri-hornblende-cummingtonite-phlogopite/biotite macrocrysts mantled by plagioclase (labradorite to oligoclase)-quartz coronas. The gabbros are LILE- and LREE-enriched, transitional arc-like rocks that formed from a different melt source and parental magma than the quartz diorite body. The quartz diorite is plagioclase-rich (50 modal % andesine), contains only trace cummingtonite, lacks phlogopite, and preserves rare diopside overgrown by magnesio-ferri-hornblende. This intrusion is more alkaline and OIB-like than the quartz gabbros and exhibits the influence of a deeper, more enriched mantle component, although both melts variably interacted with deep lithosphere. The quartz gabbro dykes and quartz diorite body may represent melts of the lower lithosphere and upper asthenosphere, respectively.&lt;/div&gt;&lt;div&gt;The abundance of coarse- to medium-grained amphibole and phlogopite/biotite in the samples is consistent with crystallization of hydrous magmas and rapid, water-enhanced crystal growth, with cooling paths recorded by chemically zoned grains of magnesio-ferri-hornblende and plagioclase. One quartz gabbro displays reverse core to rim chemical zoning of plagioclase from andesine to labradorite, which may reflect decreasing pressure during magma ascent and crystallization, magma mixing of evolved and more primitive magmas, and/or fluctuations in H&lt;sub&gt;2&lt;/sub&gt;O content. The presence of cummingtonite suggests crystallization at relatively low temperatures in shallow, low-pressure, upper crustal magma chambers. The quartz gabbros may represent melts equivalent to the nearby Howley Islands gabbro body, whereas the quartz diorite may represent a plagioclase cumulate along the margin of another melt chamber.&lt;/div&gt;&lt;div&gt;U-Pb CA-ID-TIMS zircon geochronology yielded ages of ca. 400.3 Ma for the gabbro dykes and 399.9 Ma for the quartz diorite intrusion, within the ca. 410–377 Ma age range for mineralization of the nearby Valentine gold deposits. The ca. 400 Ma intrusions, when considered in conjunction with regional models, reflect melting and hydrous magmatism in the mantle wedge above a retreating Avalonian slab that was dehydrating during the Acadian orogenic cycle. The coincidence of Pridoli (ca. 422 Ma) to Emsian (ca. 400 Ma) bimodal magmatism and orogenic gold mineralization in central Newfoundland reflects more than twenty million years of high geothermal gradients and fluid flow, which when combined w","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107837"},"PeriodicalIF":2.9,"publicationDate":"2024-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142551880","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Multistage magmatic and post-magmatic evolution of the Neoarchaean Closepet Batholith of Dharwar Craton in southern India - insights from the texture and chemical composition of titanite","authors":"Wiktoria Gmochowska ,&nbsp;Ewa Słaby ,&nbsp;Anna Gumsley ,&nbsp;Gabriela A. Kozub-Budzyń ,&nbsp;Sourabh Bhattacharya","doi":"10.1016/j.lithos.2024.107840","DOIUrl":"10.1016/j.lithos.2024.107840","url":null,"abstract":"<div><div>Titanite is often used to describe the path of igneous, metamorphic, and hydrothermal processes. Therefore, titanite can unravel the multistage magmatic and post-magmatic evolution of granitoids. In this study, we present a comprehensive study of the ca. 2.57–2.51 Ga Closepet Batholith in the Dharwar Craton of southern India using titanite. This granitoid body provides a unique opportunity as various structural levels of the batholith are continuously outcropping. The textural and geochemical studies of titanite, supported by U<img>Pb isotopic dating, allowed us to distinguish five generations of magmatic and hydrothermal titanite. Three types of magmatic titanite demonstrate stage-growth crystallization (type I) and a change from reduced, high-temperature (type II) to oxidised, low-temperature conditions (type III). Hydrothermal titanite is recorded as altered titanite with zoned to patchy textures and secondary fractures and veinlets (type IV) and titanite inclusions within biotite (type V). Hydrothermal titanite (type IV) shows depletion in rare earth elements and high-field strength elements, indicating mobilization of those elements by a fluid. U<img>Pb dating by LA-ICP-MS of magmatic titanite type I yielded ages of ca. 2.5 Ga, consistent with the timing of formation of the Closepet Batholith. The relationship between titanite textures and chemistry indicates that titanite serves as a recorder of the multistage magmatic and post-magmatic evolution of the Closepet Batholith. In addition, our study shows that hydrothermal activity affected a large area, with fluids circulating over long distances within the upper structural levels of the Closepet Batholith.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107840"},"PeriodicalIF":2.9,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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":"Water content drives distinct evolution trajectory of Early Cretaceous granitoids in inland and coastal southeast China","authors":"Jing-Yuan Chen ,&nbsp;Jin-Hui Yang ,&nbsp;Ji-Heng Zhang ,&nbsp;Yu-Sheng Zhu ,&nbsp;Jin-Feng Sun ,&nbsp;Shao-Wei Zhao","doi":"10.1016/j.lithos.2024.107836","DOIUrl":"10.1016/j.lithos.2024.107836","url":null,"abstract":"<div><div>Water plays a crucial role in determining the crystallization sequence of magma, which subsequently influences the chemical compositions of magmatic rocks across different tectonic settings. In this study, we compared the evolutionary features of granitic rocks along the coast and inland areas of southeast China, aiming to identify the key factors influencing their evolution. Our work indicates that multiple granitic intrusions formed between 126 and 142 Ma in the coastal region of southeastern China, which is consistent with the formation ages of large-scale granitoids in the inland Gan-Hang Belt. Isotopic characteristics suggest that the granitic rocks in southern Fujian originated from the melting of juvenile crust, while those in northern Fujian and eastern Zhejiang were formed from the partial melting of ancient crustal rocks, incorporating mafic magma evolved from the mantle. Most of the granitoids from the coastal region of southeastern China exhibit low zircon saturation temperatures (680–800 °C) and Zr/Sr ratios (&lt;1), suggesting their origin from a cold, wet magma reservoir. The porphyritic quartz diorite and porphyritic monzogranite represent the residual cumulate rocks of this hydrous magma reservoir, whereas the granitic porphyry and high-silica equigranular alkali feldspar granite evolved from the felsic melts extracted from the same reservoir. In contrast, most of the Early Cretaceous granitoids in the Gan-Hang Belt, located in the inland areas of southeast China, display high zircon saturation temperatures (800–900 °C) and Zr/Sr ratios (&gt;1), indicating their origin from hot, water-poor magma reservoirs. The porphyritic granites in this region represent residual cumulate rocks formed in water-poor magma reservoirs, whereas the high-silica equigranular granites evolved from hot felsic melts extracted from similar magma reservoirs. In the Early Cretaceous, the coastal region of southeastern China was closer to the Late Mesozoic paleo-Pacific subduction zone, where crystal-melt segregation within cold, wet magma reservoirs predominantly influenced magma evolution. Conversely, the granitoids in the Gan-Hang Belt in the inland region, located farther from the Late Mesozoic paleo-Pacific subduction zone, were associated with a rift tectonic setting and formed through crystal-melt segregation within hot, water-poor magma reservoirs. Our study underscores the critical role of water content in magma reservoirs in shaping the chemical composition of granitic rocks through crystal-melt segregation, thereby deepening our understanding of crustal formation processes across diverse tectonic environments.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107836"},"PeriodicalIF":2.9,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Partial melting of HP–UHP felsic gneiss in the South Altyn Tagh reveals the rapid exhumation of a deeply subducted slab","authors":"Yongsheng Gai,&nbsp;Tuo Ma,&nbsp;Liang Liu,&nbsp;Xiaoying Liao,&nbsp;Lei Kang,&nbsp;Chao Wang,&nbsp;Wenqiang Yang","doi":"10.1016/j.lithos.2024.107835","DOIUrl":"10.1016/j.lithos.2024.107835","url":null,"abstract":"<div><div>The partial melting of HP–UHP rocks plays a crucial role in facilitating the exhumation of deeply subducted rocks. However, accurately determining the <em>P–T–t</em> conditions of the initial melting and subsequent crystallization is often challenging, which can hamper our understanding of the relationship between partial melting and exhumation. We present a detailed investigation of granitic veins in the (U)HP felsic gneiss in the eastern South Altyn Tagh (SAT), northwest China. These granitic veins have similar whole rock geochemical characteristics to those of the felsic gneiss: high K₂O (5.01–9.95 wt%) and Rb contents, and low Sr contents, with negative correlations between Rb/Sr ratios and Ba or Sr contents. This suggests that the veins were generated by muscovite-dehydration melting of the felsic gneiss. Garnet crystals in the felsic gneiss contain many titanite and multiphase solid inclusions in their mantles. Using the compositions of the garnet mantles and granitic veins, alongside pseudosection modelling of the felsic gneiss, we estimate that the initial melting conditions of the felsic gneiss occurred at 2.57–2.61 GPa and 1000 °C, just above the solidus. In situ U<img>Pb dating of titanite inclusions in the garnet mantles yields an initial melting age of ∼485 Ma. Furthermore, anatectic zircon grains in the granitic veins yield U<img>Pb ages of 488–484 Ma. Using Ti-in-zircon thermometry and ¹⁷⁶Lu/¹⁷⁷Hf-in-zircon geobarometry, we estimate that the anatectic zircon grains crystallized at 647–872 °C and 0.16–0.82 GPa. The estimated <em>P–T–t</em> path from the initial melting of the felsic gneiss to the crystallization of the granitic veins indicates rapid exhumation from ∼2.6 to 0.16–0.82 GPa. This exhumation can be attributed to partial melting, which weakened the rocks and enabled their ascent to shallower depths. Moreover, the potassic melts derived from partial melting of the felsic gneiss provide new insights into the genesis of potassic granitoids in subduction zones.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107835"},"PeriodicalIF":2.9,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Contribution of alkaline magmas to the petrogenesis of Triassic aluminous A-type granites on Liaodong Peninsula, Northeastern China","authors":"Yu-Sheng Zhu ,&nbsp;Jin-Hui Yang ,&nbsp;Jin-Feng Sun ,&nbsp;Jing-Yuan Chen ,&nbsp;Lei Xu ,&nbsp;Rui Li ,&nbsp;Bao-Quan Zhou","doi":"10.1016/j.lithos.2024.107834","DOIUrl":"10.1016/j.lithos.2024.107834","url":null,"abstract":"<div><div>Aluminous A-type granites are not typically associated with mantle-derived rocks. Their generation is usually linked to crustal melting with mantle-derived magmas primarily acting as a heat source. However, the Triassic Bolinchuan A-type granites on Liaodong Peninsula, northeastern China, coexist with a large mantle-derived alkaline igneous complex, indicating a close genetic relationship that provides new insights into the petrogenesis of aluminous A-type granites. The Bolinchuan granites were formed during 230–226 Ma, coeval with syenites in the alkaline complex (230–224 Ma). The granites are metaluminous to weakly peraluminous, but have relatively high alkali contents (8.61–9.40 wt%). Their high Ga/Al ratios, elevated Nb, Zr, Ce, and Y contents, and high magmatic temperatures (&gt;875 °C) indicate an affinity with aluminous A-type granites. However, the Bolinchuan granites have relatively high MgO contents at intermediate SiO₂ contents, with Mg# values of up to 47; these features are inconsistent with the melting of only crustal rocks. Instead, these granites contain mineral phases similar to those of the syenites and exhibit major and trace element trends that are continuous with those of the syenites. Their geochemical features include enrichments in large-ion lithophile elements (e.g., Ba and Sr), depletions in high-field-strength elements (e.g., Nb and Ta) and heavy rare earth elements, and small negative Eu anomalies, which are also consistent with the features of the associated syenites. Furthermore, the granites and their accessory minerals have high initial ⁸⁷Sr/⁸⁶Sr ratios, and low ε_Nd(t) and ε_Hf(t) values, which are similar to the syenites, apart from being slightly less isotopically enriched. These geochemical and isotopic features suggest the Bolinchuan granites formed from the syenitic magmas by fractional crystallization of alkali feldspar, amphibole, and apatite, in combination with the addition of ∼30 % juvenile crust-derived materials, as indicated by modeling. Our study reveals that differentiation of mantle-derived alkaline magmas can generate magmas parental to aluminous A-type granites. As such, the mantle not only provides the heat for the formation of aluminous A-type granites, but can also be the main source of the magmas.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107834"},"PeriodicalIF":2.9,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraints of in-situ elemental compositions and U–Pb ages of cassiterite on the origin of the Cretaceous Gejiu and Dulong tin deposits, SW China: Implications for the linkage of tin belts in SE Asia","authors":"Zhi Zhang ,&nbsp;Jie-Hua Yang ,&nbsp;Rui-Zhong Hu ,&nbsp;Bin Fu ,&nbsp;Qian Hu ,&nbsp;Mei-Fu Zhou","doi":"10.1016/j.lithos.2024.107832","DOIUrl":"10.1016/j.lithos.2024.107832","url":null,"abstract":"<div><div>The western Yunnan tin belts in SW China and the southern Myanmar tin belt in SE Asia are traditionally thought to be part of the SE Asian tin metallogenic province. However, the tectonic setting of the Youjiang tin belt in SW China and its genetic relationship to the other tin belts are poorly documented. In this belt, the giant Gejiu and Dulong tin deposits are typical of skarn-type deposits and both contain contact and distal skarn orebodies. Tin ores of distal orebodies in these two deposits are composed of cassiterite, sulfide and calcite. In both deposits, most cassiterite grains from these ores are rich in Fe and W and depleted in Nb and Ta. They have ²³⁸U/²⁰⁶Pb ages between 81.4 and 84.1 Ma, similar to hosting granitic plutons. Two generations of cassiterite with distinctly different microtextures and trace elemental compositions can be recognized. The first generation (Cst-I) is compositionally and texturally homogeneous, but the second generation (Cst-II) displays distinctly oscillatory zoning. Cst-II contains Nb, W, and U lower, and Fe, Ta, Zr and chalcophile elements (Ga, Ge, In, and Sb) higher than Cst-I. These textural and compositional variations reflect the potential involvement of meteoric water in the magmatic-hydrothermal system. In this system, ore-forming fluids were evolved to more alkaline and oxidized to facilitate the precipitation of cassiterite. Our study indicates that these two deposits in the Youjiang tin belt have mineralization styles similar to those in the adjacent western Yunnan and southern Myanmar tin belts and all these tin belts belong to the SE Asian metallogenic provinces. A westward-younging trend of tin mineralization in these three belts can be explained by the rollback of the subducted Neo-Tethyan oceanic slab. This setting is different from the one related to the subduction of the Paleo-Pacific plate.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107832"},"PeriodicalIF":2.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142536317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Petrogenesis of the Zenong Group volcanics in the central Lhasa subterrane, Tibet: Geodynamic implications of the scissor-like southward subduction of the Shiquanhe-Jiali Tethyan Ocean","authors":"Jia-jia Yu ,&nbsp;Wei Chen ,&nbsp;Ju-Xing Tang ,&nbsp;Cheng-Yang Wang ,&nbsp;Xu-Dong Ma ,&nbsp;Qing-Ping Liu ,&nbsp;Meng-Xiang Di ,&nbsp;Chang Liu","doi":"10.1016/j.lithos.2024.107831","DOIUrl":"10.1016/j.lithos.2024.107831","url":null,"abstract":"<div><div>The widespread Mesozoic volcanics in the central Lhasa subterrane have been a subject of debate concerning their genetic mechanisms. Leveraging geochronology, element geochemistry, and Hf isotopes, we have systematically investigated the origin and dynamic mechanisms of the Zenong Group volcanics in the Bengnazangbu and western Dangreyongcuo areas in the east-middle part of the central Lhasa subterrane. Comprising primarily of andesites, dacites, and rhyolites, the Zenong Group volcanics display distinct geochemical signatures. In the Dangreyongcuo and Bengnazangbu areas, the andesite, dacite, and rhyolites show medium to high-K calc-alkaline characteristics. These rocks share similarities in trace element distribution, exhibiting enrichment in Rb, U, Th, Pb, and K, but depletion in Nb, Ta, Ti, Ba, and Sr. These characteristics accord with the typical composition of arc volcanic rocks. Zircon U<img>Pb dating has revealed that the volcanic rocks in the Dangreyongcuo and Bengnazangbu areas have ages of 127–126 Ma and 112–103 Ma, respectively. Further, the distribution of zircon U<img>Pb ages suggests a west-east younging trend both in the Zenong Group and the Shiquanhe-Jiali suture zone. The ε_Hf(t) values of andesite, dacite, and rhyolite are all below the chondrite standard line, ranging from 0 to −15, and the crustal model ages range from 2.0 to 1.2 Ga. Our data, combined with the geological setting, whole-rock geochemistry, Hf isotopes, and geochronology, suggest that the Zenong Group volcanic rocks are the result of the mixing of mantle wedge melts formed by the subduction of the Shiquanhe-Jiali Ocean with the lower crust of the Lhasa terrane, and undergoing fractional crystallization of amphibole ad plagioclase. And we believe that the Shiquanhe-Jiali Ocean was sequentially closed from west to east in a scissor-like fashion during southward subduction.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"490 ","pages":"Article 107831"},"PeriodicalIF":2.9,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142658367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Timing of the subduction initiation and ophiolite emplacement of the inner Tauride Ocean: Insight from the Pınarbaşı ophiolite in Central Türkiye","authors":"Rahmi Melih Çörtük ,&nbsp;Ömer Faruk Çelik ,&nbsp;Mutlu Özkan ,&nbsp;Joshua H.F.L. Davies ,&nbsp;Andrea Marzoli","doi":"10.1016/j.lithos.2024.107833","DOIUrl":"10.1016/j.lithos.2024.107833","url":null,"abstract":"<div><div>Late Cretaceous ophiolites are widespread in southern Türkiye, including the Tauride Belt Ophiolites and the Central Anatolian Ophiolites. Here, we report new geological, geochemical, geochronological, and zircon isotopic data from ophiolitic rocks of the Pınarbaşı ophiolite (Eastern Tauride Belt). The Pınarbaşı ophiolite forms incomplete sequences, with its mantle section dominated by serpentinized harzburgite and chromitites, while the crustal section comprises ultramafic and mafic cumulates. Whole-rock and mineral chemistry data suggest a supra-subduction zone origin. LA-ICP-MS zircon U-Pb age of 88.2 ± 0.4 Ma (MSWD = 0.84) was obtained from a plagiogranite dyke cutting serpentinized peridotite of the Pınarbaşı ophiolite. Another, U-Pb zircon crystallization age of 96.8 ± 0.6 Ma (MSWD = 1.53) was obtained from a plagiogranite dyke within the mélange of the Pınarbaşı ophiolite. Hafnium isotope compositions of these zircons (εHf(t) = +26.4 to +3.1) suggest a depleted to slightly enriched mantle source. The formation ages of the crustal rocks (gabbro, plagiogranite, and dolerite) of the Cretaceous ophiolites in the Tauride Belt from this and previous ophiolite occurrences, suggest that supra-subduction zone ophiolites in the Inner Tauride Ocean formed during the period ∼101–87 Ma. On the other hand, the peak metamorphism of the metamorphic sole rocks is reported to have occurred around ∼104 Ma. According to all available petrogenetic and geochronological data, it is considered that the supra-subduction zone crust developed shortly (∼ 3–4 Myr) after the initiation of intra-oceanic subduction and this lasted ∼10–15 Myr.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107833"},"PeriodicalIF":2.9,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142442934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraints of upper crust magmatic processes on the formation of Saindak porphyry Cu deposit: Insights from mineral geochemistry","authors":"Lu Wang ,&nbsp;Zi-xuan Wang ,&nbsp;Yuan-chuan Zheng ,&nbsp;Zeng-qian Hou ,&nbsp;Zhu-sen Yang ,&nbsp;Chang-da Wu ,&nbsp;Xin Li","doi":"10.1016/j.lithos.2024.107829","DOIUrl":"10.1016/j.lithos.2024.107829","url":null,"abstract":"<div><div>Upper crustal magmatic processes play a crucial role in linking the magmatic and hydrothermal systems of porphyry deposits, ultimately controlling the generation of ore-forming fluids. Understanding these processes within a magma chamber is essential for deciphering the formation of porphyry deposits. The Saindak deposit, a large porphyry Cu system in the western Chagai belt, features coeval ore-forming and barren magma pulses, providing key insights into the characterization of porphyry systems. In this study, detailed petrographic observations and geochemical analyses of amphibole, plagioclase, and apatite were conducted to unravel the magmatic evolution at Saindak. Based on textural relationships and crystallization sequences, three distinct populations of amphibole in the ore-forming magma were identified. These amphiboles record the entire fractional crystallization process of magma that initially emplaced at a depth of ∼5 km to the connected magma system at ∼2 km. The study of amphibole and apatite reveals that the fertile magma underwent large-scale fluid exsolution in an open system. The simultaneous and rapid depletion of Cu, Cl, S, and H₂O in the magma indicates that Cl and S were highly partitioned into the exsolved fluid phase. These elements formed complexes, which effectively concentrated metals in the fluid. Conversely, the barren magma was characterized by either low metal content or limited fluid exsolution within the magma chamber. Overall, we reconstruct the upper crustal magmatic processes at Saindak and conclude that efficient extraction of Cu through fluid exsolution is the key to porphyry deposit formation.</div></div>","PeriodicalId":18070,"journal":{"name":"Lithos","volume":"488 ","pages":"Article 107829"},"PeriodicalIF":2.9,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142438344","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}