{"title":"高硅方解石的形成及其与板块断裂的关系:对生成肥沃的铜-金-钼斑岩系统的影响","authors":"","doi":"10.1016/j.gsf.2024.101927","DOIUrl":null,"url":null,"abstract":"<div><p>In recent years, the characteristics and sources of fertile adakites has received considerable attention. As well, most recently the geodynamic environment of convergent margins subducting oceanic crust aiding arc formation, evolving to slab rollback, then slab break-off after collision (i.e. late- to post-collisional slab failure (arc-like magmatism) and transpression) has gained more recognition, although their relationship to each other has yet to be explored. The geochemical characteristics imply that adakites/adakite-like, in particular high-silica adakites (HSA), can form by partial melting of subducting hydrothermally altered oceanic crust in convergent plate boundary settings during the terminal stages of subduction, lithosphere thickening, and then failure (all late to post collisional), while the melting of the mantle wedge during subduction-related dehydration creates more typical calc-alkaline basalt-andesite-dacite-rhyolite series (ADR) to form intraoceanic island arc to intracontinental margin arc systems, before the collisional stage. HSAs are characterized by high-silica (SiO<sub>2</sub> > 67 wt.%), Al<sub>2</sub>O<sub>3</sub> > 15 wt.%, Sr > 300 ppm, Y<20 ppm, Yb < 1.8 ppm, and Nb ≤ 10 ppm, and MgO < 3 wt.%, with high Sr/Y (>50), and La/Yb (>10). Some specific geochemical features, such as high Mg# (ave 0.51), Ni (ave 924 ppm), and Cr (ave 36 ppm), in HSAs are typical, in contrast to calc-alkaline arcs, although both groups display similar but less pronounced negative anomalies of Nb, Ta, and Ti in primitive mantle-normalized trace element spider diagram profiles. These unique geochemical features are likely ascribed to the involvement of garnet, hornblende, and titanite either during partial melting of hydrous MORB-like oceanic crust with only minor assimilation and fractional crystallization (AFC) within the mantle and crustal during ascent in a transpressional collisional environment. Hypotheses for origin of HSA derivative from melting in convergent margins from young, hot oceanic plates subducting into the mantle is applicable to only some adakitic systems. The difference in geochemical characteristics of adakites compared to ADR, such as relative higher MgO, Cr, Cu, and Ni, are due to their slab source, as well as interaction of the slab-derived adakitic melts with overlying hot lithospheric mantle; altered oceanic slabs are also relatively rich in siderophile and other chalcophile elements, as well as sulfates and sulfides. HSA magmas related to slab failure have special geochemical properties, such as Sr/Y > 20, Nb/Y > 0.4, Ta/Yb > 0.3, La/Yb > 10, Gd/Yb > 2, and Sm/Yb > 2.5. Slightly higher Nb + Ta is due to high <em>T</em> melting of rutile. Varieties of Nb/Ta compared to silica are also significant in HSA as a result of slab failure (roll back to break-off). High <em>T</em>-<em>P</em> partial melting of the hydrothermally altered oceanic slab produces HSA with quite high activities of H<sub>2</sub>O, SO<sub>2</sub>, HCl, with chalcophile metals that remain incompatible at higher <em>f</em>O<sub>2</sub> (low <em>f</em>H<sub>2</sub>); these situations happen in late- to post-collisional settings where the subducting oceanic crust experienced slab failure, resulting in advective heat addition to the system from upwelling asthenosphere. In such a slab failure setting, transpression and transtension play a significant role in the rapid emplacement of a high amount of fertile adakitic magmas through the subduction-modified lithosphere and crust into the upper crust. When oxidized slab melts interact with the subduction-modified lithospheric mantle, the resulting magmas stay oxidized, potentially contributing to the special conditions conducive to formation of porphyry Cu-Au mineralization.</p></div>","PeriodicalId":12711,"journal":{"name":"Geoscience frontiers","volume":null,"pages":null},"PeriodicalIF":8.5000,"publicationDate":"2024-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S1674987124001518/pdfft?md5=ba2bc6b1a17fb58b1e913047e8b1ce72&pid=1-s2.0-S1674987124001518-main.pdf","citationCount":"0","resultStr":"{\"title\":\"Formation of high-silica adakites and their relationship with slab break-off: Implications for generating fertile Cu-Au-Mo porphyry systems\",\"authors\":\"\",\"doi\":\"10.1016/j.gsf.2024.101927\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>In recent years, the characteristics and sources of fertile adakites has received considerable attention. As well, most recently the geodynamic environment of convergent margins subducting oceanic crust aiding arc formation, evolving to slab rollback, then slab break-off after collision (i.e. late- to post-collisional slab failure (arc-like magmatism) and transpression) has gained more recognition, although their relationship to each other has yet to be explored. The geochemical characteristics imply that adakites/adakite-like, in particular high-silica adakites (HSA), can form by partial melting of subducting hydrothermally altered oceanic crust in convergent plate boundary settings during the terminal stages of subduction, lithosphere thickening, and then failure (all late to post collisional), while the melting of the mantle wedge during subduction-related dehydration creates more typical calc-alkaline basalt-andesite-dacite-rhyolite series (ADR) to form intraoceanic island arc to intracontinental margin arc systems, before the collisional stage. HSAs are characterized by high-silica (SiO<sub>2</sub> > 67 wt.%), Al<sub>2</sub>O<sub>3</sub> > 15 wt.%, Sr > 300 ppm, Y<20 ppm, Yb < 1.8 ppm, and Nb ≤ 10 ppm, and MgO < 3 wt.%, with high Sr/Y (>50), and La/Yb (>10). Some specific geochemical features, such as high Mg# (ave 0.51), Ni (ave 924 ppm), and Cr (ave 36 ppm), in HSAs are typical, in contrast to calc-alkaline arcs, although both groups display similar but less pronounced negative anomalies of Nb, Ta, and Ti in primitive mantle-normalized trace element spider diagram profiles. These unique geochemical features are likely ascribed to the involvement of garnet, hornblende, and titanite either during partial melting of hydrous MORB-like oceanic crust with only minor assimilation and fractional crystallization (AFC) within the mantle and crustal during ascent in a transpressional collisional environment. Hypotheses for origin of HSA derivative from melting in convergent margins from young, hot oceanic plates subducting into the mantle is applicable to only some adakitic systems. The difference in geochemical characteristics of adakites compared to ADR, such as relative higher MgO, Cr, Cu, and Ni, are due to their slab source, as well as interaction of the slab-derived adakitic melts with overlying hot lithospheric mantle; altered oceanic slabs are also relatively rich in siderophile and other chalcophile elements, as well as sulfates and sulfides. HSA magmas related to slab failure have special geochemical properties, such as Sr/Y > 20, Nb/Y > 0.4, Ta/Yb > 0.3, La/Yb > 10, Gd/Yb > 2, and Sm/Yb > 2.5. Slightly higher Nb + Ta is due to high <em>T</em> melting of rutile. Varieties of Nb/Ta compared to silica are also significant in HSA as a result of slab failure (roll back to break-off). High <em>T</em>-<em>P</em> partial melting of the hydrothermally altered oceanic slab produces HSA with quite high activities of H<sub>2</sub>O, SO<sub>2</sub>, HCl, with chalcophile metals that remain incompatible at higher <em>f</em>O<sub>2</sub> (low <em>f</em>H<sub>2</sub>); these situations happen in late- to post-collisional settings where the subducting oceanic crust experienced slab failure, resulting in advective heat addition to the system from upwelling asthenosphere. In such a slab failure setting, transpression and transtension play a significant role in the rapid emplacement of a high amount of fertile adakitic magmas through the subduction-modified lithosphere and crust into the upper crust. When oxidized slab melts interact with the subduction-modified lithospheric mantle, the resulting magmas stay oxidized, potentially contributing to the special conditions conducive to formation of porphyry Cu-Au mineralization.</p></div>\",\"PeriodicalId\":12711,\"journal\":{\"name\":\"Geoscience frontiers\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":8.5000,\"publicationDate\":\"2024-09-10\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.sciencedirect.com/science/article/pii/S1674987124001518/pdfft?md5=ba2bc6b1a17fb58b1e913047e8b1ce72&pid=1-s2.0-S1674987124001518-main.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Geoscience frontiers\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S1674987124001518\",\"RegionNum\":1,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"GEOSCIENCES, MULTIDISCIPLINARY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geoscience frontiers","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1674987124001518","RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOSCIENCES, MULTIDISCIPLINARY","Score":null,"Total":0}
Formation of high-silica adakites and their relationship with slab break-off: Implications for generating fertile Cu-Au-Mo porphyry systems
In recent years, the characteristics and sources of fertile adakites has received considerable attention. As well, most recently the geodynamic environment of convergent margins subducting oceanic crust aiding arc formation, evolving to slab rollback, then slab break-off after collision (i.e. late- to post-collisional slab failure (arc-like magmatism) and transpression) has gained more recognition, although their relationship to each other has yet to be explored. The geochemical characteristics imply that adakites/adakite-like, in particular high-silica adakites (HSA), can form by partial melting of subducting hydrothermally altered oceanic crust in convergent plate boundary settings during the terminal stages of subduction, lithosphere thickening, and then failure (all late to post collisional), while the melting of the mantle wedge during subduction-related dehydration creates more typical calc-alkaline basalt-andesite-dacite-rhyolite series (ADR) to form intraoceanic island arc to intracontinental margin arc systems, before the collisional stage. HSAs are characterized by high-silica (SiO2 > 67 wt.%), Al2O3 > 15 wt.%, Sr > 300 ppm, Y<20 ppm, Yb < 1.8 ppm, and Nb ≤ 10 ppm, and MgO < 3 wt.%, with high Sr/Y (>50), and La/Yb (>10). Some specific geochemical features, such as high Mg# (ave 0.51), Ni (ave 924 ppm), and Cr (ave 36 ppm), in HSAs are typical, in contrast to calc-alkaline arcs, although both groups display similar but less pronounced negative anomalies of Nb, Ta, and Ti in primitive mantle-normalized trace element spider diagram profiles. These unique geochemical features are likely ascribed to the involvement of garnet, hornblende, and titanite either during partial melting of hydrous MORB-like oceanic crust with only minor assimilation and fractional crystallization (AFC) within the mantle and crustal during ascent in a transpressional collisional environment. Hypotheses for origin of HSA derivative from melting in convergent margins from young, hot oceanic plates subducting into the mantle is applicable to only some adakitic systems. The difference in geochemical characteristics of adakites compared to ADR, such as relative higher MgO, Cr, Cu, and Ni, are due to their slab source, as well as interaction of the slab-derived adakitic melts with overlying hot lithospheric mantle; altered oceanic slabs are also relatively rich in siderophile and other chalcophile elements, as well as sulfates and sulfides. HSA magmas related to slab failure have special geochemical properties, such as Sr/Y > 20, Nb/Y > 0.4, Ta/Yb > 0.3, La/Yb > 10, Gd/Yb > 2, and Sm/Yb > 2.5. Slightly higher Nb + Ta is due to high T melting of rutile. Varieties of Nb/Ta compared to silica are also significant in HSA as a result of slab failure (roll back to break-off). High T-P partial melting of the hydrothermally altered oceanic slab produces HSA with quite high activities of H2O, SO2, HCl, with chalcophile metals that remain incompatible at higher fO2 (low fH2); these situations happen in late- to post-collisional settings where the subducting oceanic crust experienced slab failure, resulting in advective heat addition to the system from upwelling asthenosphere. In such a slab failure setting, transpression and transtension play a significant role in the rapid emplacement of a high amount of fertile adakitic magmas through the subduction-modified lithosphere and crust into the upper crust. When oxidized slab melts interact with the subduction-modified lithospheric mantle, the resulting magmas stay oxidized, potentially contributing to the special conditions conducive to formation of porphyry Cu-Au mineralization.
Geoscience frontiersEarth and Planetary Sciences-General Earth and Planetary Sciences
CiteScore
17.80
自引率
3.40%
发文量
147
审稿时长
35 days
期刊介绍:
Geoscience Frontiers (GSF) is the Journal of China University of Geosciences (Beijing) and Peking University. It publishes peer-reviewed research articles and reviews in interdisciplinary fields of Earth and Planetary Sciences. GSF covers various research areas including petrology and geochemistry, lithospheric architecture and mantle dynamics, global tectonics, economic geology and fuel exploration, geophysics, stratigraphy and paleontology, environmental and engineering geology, astrogeology, and the nexus of resources-energy-emissions-climate under Sustainable Development Goals. The journal aims to bridge innovative, provocative, and challenging concepts and models in these fields, providing insights on correlations and evolution.