{"title":"日本东北部山梨县上佐野安卡拉米特玄武岩尖晶石中的透辉石巨晶中的花岗岩熔体和碳流包裹体","authors":"Takashi Amagai, Masanori Kurosawa","doi":"10.1111/rge.12324","DOIUrl":null,"url":null,"abstract":"Large phenocrysts, known as megacrysts, are focal points for research due to their ability to encapsulate large inclusions suitable for precise chemical analyses. Ankaramite, a distinctive type of undifferentiated volcanic rock, stands out due to its high MgO and CaO contents and the presence of abundant Ca-rich clinopyroxene (diopside) and less common Mg-rich olivine phenocrysts. In this study, granitic melt inclusions together with carbonic fluid inclusions were identified within diopside megacrysts of ankaramitic basalt dikes in the Kamisano region, Yamanashi Prefecture, Japan. The identified melt inclusions are completely crystallized and primarily composed of quartz, alkali feldspar, and plagioclase, with smaller amounts of pargasite, augite, apatite, and sulfides. Small amounts of residual glass were also occasionally observed in the inclusions. The average chemical composition of these granitic melts within the inclusions corresponds to that of calc-alkaline granodiorite and the melts are characterized by low water content (0.38 wt%) and high concentrations of sulfur (7000 ppm), copper, and iron. The findings suggested that the composition of granitic melt inclusions may provide insights into the characteristics of near-surface hydrothermal metal ore deposits. The diopside megacrysts also contain CO<sub>2</sub><span></span>H<sub>2</sub>O fluid inclusions, which are completely crystallized and mainly comprised of calcite and chlorite, along with small amounts of quartz. The crystals are interpreted to have formed by the reaction of original CO<sub>2</sub><span></span>H<sub>2</sub>O fluids and host diopside. The diopside megacrysts are estimated to have started crystallization from tholeiitic basalt at a depth of ~30 km in the lower crust, and trapped fluids and granitic melts as inclusions at a shallower depth when the tholeiitic magma ascended.","PeriodicalId":21089,"journal":{"name":"Resource Geology","volume":"8 7 1","pages":""},"PeriodicalIF":1.1000,"publicationDate":"2023-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Granitic-melt and carbonic-fluid inclusions in diopside megacrysts from ankaramitic basalt dikes at Kamisano, Yamanashi prefecture, northeastern Japan\",\"authors\":\"Takashi Amagai, Masanori Kurosawa\",\"doi\":\"10.1111/rge.12324\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Large phenocrysts, known as megacrysts, are focal points for research due to their ability to encapsulate large inclusions suitable for precise chemical analyses. Ankaramite, a distinctive type of undifferentiated volcanic rock, stands out due to its high MgO and CaO contents and the presence of abundant Ca-rich clinopyroxene (diopside) and less common Mg-rich olivine phenocrysts. In this study, granitic melt inclusions together with carbonic fluid inclusions were identified within diopside megacrysts of ankaramitic basalt dikes in the Kamisano region, Yamanashi Prefecture, Japan. The identified melt inclusions are completely crystallized and primarily composed of quartz, alkali feldspar, and plagioclase, with smaller amounts of pargasite, augite, apatite, and sulfides. Small amounts of residual glass were also occasionally observed in the inclusions. The average chemical composition of these granitic melts within the inclusions corresponds to that of calc-alkaline granodiorite and the melts are characterized by low water content (0.38 wt%) and high concentrations of sulfur (7000 ppm), copper, and iron. The findings suggested that the composition of granitic melt inclusions may provide insights into the characteristics of near-surface hydrothermal metal ore deposits. The diopside megacrysts also contain CO<sub>2</sub><span></span>H<sub>2</sub>O fluid inclusions, which are completely crystallized and mainly comprised of calcite and chlorite, along with small amounts of quartz. The crystals are interpreted to have formed by the reaction of original CO<sub>2</sub><span></span>H<sub>2</sub>O fluids and host diopside. The diopside megacrysts are estimated to have started crystallization from tholeiitic basalt at a depth of ~30 km in the lower crust, and trapped fluids and granitic melts as inclusions at a shallower depth when the tholeiitic magma ascended.\",\"PeriodicalId\":21089,\"journal\":{\"name\":\"Resource Geology\",\"volume\":\"8 7 1\",\"pages\":\"\"},\"PeriodicalIF\":1.1000,\"publicationDate\":\"2023-12-13\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Resource Geology\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.1111/rge.12324\",\"RegionNum\":4,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"GEOLOGY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Resource Geology","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1111/rge.12324","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOLOGY","Score":null,"Total":0}
Granitic-melt and carbonic-fluid inclusions in diopside megacrysts from ankaramitic basalt dikes at Kamisano, Yamanashi prefecture, northeastern Japan
Large phenocrysts, known as megacrysts, are focal points for research due to their ability to encapsulate large inclusions suitable for precise chemical analyses. Ankaramite, a distinctive type of undifferentiated volcanic rock, stands out due to its high MgO and CaO contents and the presence of abundant Ca-rich clinopyroxene (diopside) and less common Mg-rich olivine phenocrysts. In this study, granitic melt inclusions together with carbonic fluid inclusions were identified within diopside megacrysts of ankaramitic basalt dikes in the Kamisano region, Yamanashi Prefecture, Japan. The identified melt inclusions are completely crystallized and primarily composed of quartz, alkali feldspar, and plagioclase, with smaller amounts of pargasite, augite, apatite, and sulfides. Small amounts of residual glass were also occasionally observed in the inclusions. The average chemical composition of these granitic melts within the inclusions corresponds to that of calc-alkaline granodiorite and the melts are characterized by low water content (0.38 wt%) and high concentrations of sulfur (7000 ppm), copper, and iron. The findings suggested that the composition of granitic melt inclusions may provide insights into the characteristics of near-surface hydrothermal metal ore deposits. The diopside megacrysts also contain CO2H2O fluid inclusions, which are completely crystallized and mainly comprised of calcite and chlorite, along with small amounts of quartz. The crystals are interpreted to have formed by the reaction of original CO2H2O fluids and host diopside. The diopside megacrysts are estimated to have started crystallization from tholeiitic basalt at a depth of ~30 km in the lower crust, and trapped fluids and granitic melts as inclusions at a shallower depth when the tholeiitic magma ascended.
期刊介绍:
Resource Geology is an international journal focusing on economic geology, geochemistry and environmental geology. Its purpose is to contribute to the promotion of earth sciences related to metallic and non-metallic mineral deposits mainly in Asia, Oceania and the Circum-Pacific region, although other parts of the world are also considered.
Launched in 1998 by the Society for Resource Geology, the journal is published quarterly in English, making it more accessible to the international geological community. The journal publishes high quality papers of interest to those engaged in research and exploration of mineral deposits.