{"title":"褐辉石闪长岩记录了中上地壳的岩浆运移和结晶过程:德国西埃费尔地区 Rockeskyllerkopf 火山群案例研究","authors":"Cliff S J Shaw","doi":"10.1093/petrology/egae035","DOIUrl":null,"url":null,"abstract":"Clinopyroxenite xenoliths comprised of cumulus clinopyroxene ± amphibole together with intercumulus phlogopite ± olivine ± apatite ± titanite form a large part of the xenolith load in the oldest deposits of the Rockeskyllerkopf Volcanic Complex (RVC) in the West Eifel volcanic field. The xenoliths also contain xenocrysts of olivine and clinopyroxene derived from mantle peridotite and clinopyroxene from lower crustal granulite. The clinopyroxenite xenoliths are divided into five groups on the basis of their modal mineralogy and mineral compositions. Groups 1 to 4 define a continuous compositional trend indicative of fractionation of a mafic alkaline magma. Group 5 xenoliths are compositionally distinct and have been tentatively linked to high pressure crystallization of phonolitic magma within the RVC system. Thermobarometry of the group 1 – 4 xenoliths indicates that they crystallised between 1 and 4 kilobars, equivalent to a depth of 4-14 km. Group 1 -3 xenoliths all crystallised at between 1050 and 1150 °C whereas the amphibole-rich group 4 xenoliths give temperature estimates of ~ 900 °C. The clinopyroxenites share a common parent magma with clinopyroxene – phlogopite veins found in subcontinental lithospheric mantle xenoliths. However, the vein forming mama was richer in incompatible elements, in particular Zr and Hf and is interpreted to be an early formed batch of magma with the clinopyroxenites crystallising from magma derived from the same mantle, which had been depleted by the earlier phase of melting. Intrusion of magma began around 155 ky prior to the eruption of the RVC. Fe-Mg interdiffusion profiles in zoned clinopyroxene show that the magma that formed the xenoliths was present in the crust for up to 28 ky prior to the eruption. However, most samples give interdiffusion times between 1.5 and 9.9 ky. Based on xenocryst residence times and the calculated P-T conditions for clinopyroxene, there were at least seven separate batches of magma emplaced below Rockeskyllerkopf, probably as sills.","PeriodicalId":16751,"journal":{"name":"Journal of Petrology","volume":"31 1","pages":""},"PeriodicalIF":3.5000,"publicationDate":"2024-03-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Clinopyroxenite xenoliths record magma transport and crystallisation in the middle and upper crust: A case study from the Rockeskyllerkopf Volcanic Complex, West Eifel, Germany\",\"authors\":\"Cliff S J Shaw\",\"doi\":\"10.1093/petrology/egae035\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Clinopyroxenite xenoliths comprised of cumulus clinopyroxene ± amphibole together with intercumulus phlogopite ± olivine ± apatite ± titanite form a large part of the xenolith load in the oldest deposits of the Rockeskyllerkopf Volcanic Complex (RVC) in the West Eifel volcanic field. The xenoliths also contain xenocrysts of olivine and clinopyroxene derived from mantle peridotite and clinopyroxene from lower crustal granulite. The clinopyroxenite xenoliths are divided into five groups on the basis of their modal mineralogy and mineral compositions. Groups 1 to 4 define a continuous compositional trend indicative of fractionation of a mafic alkaline magma. Group 5 xenoliths are compositionally distinct and have been tentatively linked to high pressure crystallization of phonolitic magma within the RVC system. Thermobarometry of the group 1 – 4 xenoliths indicates that they crystallised between 1 and 4 kilobars, equivalent to a depth of 4-14 km. Group 1 -3 xenoliths all crystallised at between 1050 and 1150 °C whereas the amphibole-rich group 4 xenoliths give temperature estimates of ~ 900 °C. The clinopyroxenites share a common parent magma with clinopyroxene – phlogopite veins found in subcontinental lithospheric mantle xenoliths. However, the vein forming mama was richer in incompatible elements, in particular Zr and Hf and is interpreted to be an early formed batch of magma with the clinopyroxenites crystallising from magma derived from the same mantle, which had been depleted by the earlier phase of melting. Intrusion of magma began around 155 ky prior to the eruption of the RVC. Fe-Mg interdiffusion profiles in zoned clinopyroxene show that the magma that formed the xenoliths was present in the crust for up to 28 ky prior to the eruption. However, most samples give interdiffusion times between 1.5 and 9.9 ky. Based on xenocryst residence times and the calculated P-T conditions for clinopyroxene, there were at least seven separate batches of magma emplaced below Rockeskyllerkopf, probably as sills.\",\"PeriodicalId\":16751,\"journal\":{\"name\":\"Journal of Petrology\",\"volume\":\"31 1\",\"pages\":\"\"},\"PeriodicalIF\":3.5000,\"publicationDate\":\"2024-03-28\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Petrology\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://doi.org/10.1093/petrology/egae035\",\"RegionNum\":2,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"GEOCHEMISTRY & GEOPHYSICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Petrology","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1093/petrology/egae035","RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
Clinopyroxenite xenoliths record magma transport and crystallisation in the middle and upper crust: A case study from the Rockeskyllerkopf Volcanic Complex, West Eifel, Germany
Clinopyroxenite xenoliths comprised of cumulus clinopyroxene ± amphibole together with intercumulus phlogopite ± olivine ± apatite ± titanite form a large part of the xenolith load in the oldest deposits of the Rockeskyllerkopf Volcanic Complex (RVC) in the West Eifel volcanic field. The xenoliths also contain xenocrysts of olivine and clinopyroxene derived from mantle peridotite and clinopyroxene from lower crustal granulite. The clinopyroxenite xenoliths are divided into five groups on the basis of their modal mineralogy and mineral compositions. Groups 1 to 4 define a continuous compositional trend indicative of fractionation of a mafic alkaline magma. Group 5 xenoliths are compositionally distinct and have been tentatively linked to high pressure crystallization of phonolitic magma within the RVC system. Thermobarometry of the group 1 – 4 xenoliths indicates that they crystallised between 1 and 4 kilobars, equivalent to a depth of 4-14 km. Group 1 -3 xenoliths all crystallised at between 1050 and 1150 °C whereas the amphibole-rich group 4 xenoliths give temperature estimates of ~ 900 °C. The clinopyroxenites share a common parent magma with clinopyroxene – phlogopite veins found in subcontinental lithospheric mantle xenoliths. However, the vein forming mama was richer in incompatible elements, in particular Zr and Hf and is interpreted to be an early formed batch of magma with the clinopyroxenites crystallising from magma derived from the same mantle, which had been depleted by the earlier phase of melting. Intrusion of magma began around 155 ky prior to the eruption of the RVC. Fe-Mg interdiffusion profiles in zoned clinopyroxene show that the magma that formed the xenoliths was present in the crust for up to 28 ky prior to the eruption. However, most samples give interdiffusion times between 1.5 and 9.9 ky. Based on xenocryst residence times and the calculated P-T conditions for clinopyroxene, there were at least seven separate batches of magma emplaced below Rockeskyllerkopf, probably as sills.
期刊介绍:
The Journal of Petrology provides an international forum for the publication of high quality research in the broad field of igneous and metamorphic petrology and petrogenesis. Papers published cover a vast range of topics in areas such as major element, trace element and isotope geochemistry and geochronology applied to petrogenesis; experimental petrology; processes of magma generation, differentiation and emplacement; quantitative studies of rock-forming minerals and their paragenesis; regional studies of igneous and meta morphic rocks which contribute to the solution of fundamental petrological problems; theoretical modelling of petrogenetic processes.