Two-pyroxene thermobarometry with new experimental data in the system CaO-MgO-Al2O3-SiO2

Gasparik, Tibor

doi:10.1007/bf00371405

Cited by 220 publications

(90 citation statements)

References 21 publications

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“…This regular decrease of the chromium content with crystallization is well observed in the large oikocryst in the ophitic rocks. The low alumina contents and low Al VI /Al IV ratios of the clinopyroxenes, even in the microphenocrysts present in the olivine-plagioclase-clinopyroxene-phyric basalts (Units 60 and 70), are in accordance with low-pressure crystallizing conditions (Aoki and Kushiro, 1968;Gasparik, 1984).…”

Section: Pyroxenessupporting

confidence: 56%

Mineral chemistry of volcanic sequences from Hole 917A, southeast Greenland Margin

Demant¹

1998

Proceedings of the Ocean Drilling Program

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During Ocean Drilling Program Leg 152, a 779-m-thick volcanic sequence was drilled at Hole 917A, on the feather edge of the seaward-dipping reflector sequence. The volcanic succession, which erupted under subaerial conditions, was subdivided into three series (Upper, Middle, and Lower) and 92 flow units. The Upper Series comprises picrites and olivine-phyric basalts. The Middle Series basalts are more evolved, and dacitic lavas and tuffs were erupted at the base of this series. Lavas from the Lower Series show a wider compositional range. A detailed mineralogical study of the different petrographical types shows that olivine is the principal phenocryst phase in the basalts, whereas clinopyroxene and plagioclase are the main components of the groundmass. High-Mg olivines (up to Fo 92.4 ) with chrome-spinel inclusions are abundant in the picrites and olivine-phyric basalts. Fo-content of the olivine decreases as a function of the composition of the whole rock except in some aphyric basalts with ophitic textures where the olivine underwent further re-equilibration during cooling. Plagioclase exhibits a large compositional range from bytownite (An 91 ) in the more primitive basalts to oligoclase (An 21 ) for the late crystallizing feldspar in the ophitic textures. Plagioclases from the Upper Series lavas are very poor in K 2 O. The presence of bytownite phenocrysts (An 86− 66 ) associated with sodic sieve-textured plagioclase (An 36−26 ) in the dacite (Unit 54) clearly demonstrates that this lava is a mixed lava. Pyroxenes are mainly clinopyroxene, but pigeonite and orthopyroxene were found in the matrix of some differentiated basalts with ophitic textures. The low Ti contents of the pyroxenes and the evolution trends are typical of tholeiitic lavas. The development of sector zoning in pyroxene microphenocrysts of the more differentiated basalts has a scattering effect on the distribution of the points on the pyroxene quadrilateral. Opaque oxides crystallize late and are mainly titanomagnetite. Ilmenite is also present in some lavas.The volcanic succession drilled at Hole 917A presents many petrographical and mineralogical similarities to the flood basalts of the Scoresby Sund region in East Greenland. These thick basaltic sequences, which characterize the North Atlantic volcanic rifted margins, were emplaced during a short time interval during the phase of continental breakup. The Lower and Middle Series have evolved in crustal magma chambers. The frequency of picrites in the Upper Series emphasizes an easier access of more primitive magmas to the surface during the final phase of rifting.

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Section: Pyroxenessupporting

confidence: 56%

Mineral chemistry of volcanic sequences from Hole 917A, southeast Greenland Margin

Demant¹

1998

Proceedings of the Ocean Drilling Program

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“…There are no significant equilibrium temperature discrepancies among the results using the various calibration methods, the difference between the estimated values being <20°C, which strongly suggests that the minerals are in complete chemical equilibrium and our estimations are reliable. As stated above, the temperatures obtained in this study agree with the range of previous temperature estimates for mantle xenoliths from the northwestern Ethiopia plateau (875-990°C, Conticelli et al, 1999;Roger et al, 1999;947-1015°C, Ferrando et al, 2008930-1050°C, Beccaluva et al, 2009950-1050°C, Beccaluva et al, 2011 and for stability field of spinel peridotite (900-1100°C; Gasparik, 1984).…”

Section: Equilibrium Temperature and Pressure Estimatessupporting

confidence: 91%

“…The two barometers yield nearly identical ranges of equilibrium pressures (T M = 13-17 kb; T NU = 12-15 kb) in the stability field of spinel peridotites (O'Neill, 1981;Gasparik, 1984). Previous studies yielded similar pressures for mantle xenoliths from the northwestern Ethiopian plateau (10.1-13.9 kb, Conticelli et al, 1999;13-20 kb, Ferrando et al, 2008;9-12.5 kb, Beccaluva et al, 2009;9-13 kb, Beccaluva et al, 2011).…”

Section: Equilibrium Temperature and Pressure Estimatesmentioning

confidence: 92%

“…In this study, we used two-pyroxene (Wells, 1977; T W ), Cr-Al-in-orthopyroxene (Witt-Eickschen and Seck, 1991; T WS ) and Ca-in-orthopyroxene ; T BK ) geothermometers for the temperature estimations. For pressure dependent geothermometer of Brey and Köhler (1990), the equilibrium temperatures were estimated using an assumed equilibration pressure of 15 kb in the spinel peridotite stability field (Gasparik, 1984). The spinel lherzolites in this study exhibit equilibrium temperatures in the ranges of 921-973°C for T W ; 913-965°C for T WS and 918-972°C for T BK .…”

Section: Equilibrium Temperature and Pressure Estimatesmentioning

confidence: 99%

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Geochemical and Sr–Nd–Pb isotopic compositions of lithospheric mantle: Spinel lherzolites in alkaline basalts from the northwestern Ethiopian plateau

Meshesha¹,

Shinjo

Orihashi

2014

Journal of Mineralogical and Petrological Sciences

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The geochemical characteristics of mantle xenoliths (spinel lherzolites) in Quaternary alkaline basalts from the northwestern Ethiopian plateau provide new insight into the conditions of melting associated with the Afar plume. The major element compositions of the spinel lherzolites are in the range of those of the primitive mantle. The high modal content of the clinopyroxene (14-23%) indicate that the mantle xenoliths are fertile spinel lherzolites that have experienced insignificant partial melting. However, enrichment in highly incompatible elements (LREE, Ba, Pb, Th, and U) and the absence of any typical metasomatic minerals indicate that the spinel lherzolites underwent an event of later cryptic metasomatic enrichment induced by plume-related, hydrous fluid-rich silicate melts. The

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“…Figure 1. P-T conditions of the four runs (#1, #2, #3, and #4) of the high-pressure experiment superimposed on a petrogenetic grid for the model system CaO-MgO-Al 2 O 3 -SiO 2 , which was modified from Gasparik (1984). The solidus shown is for peridotite.…”

Section: Results and Datamentioning

confidence: 99%

Experimental synthesis of isochemical kelyphite — a preliminary report

Obata

Ohi

Miyake

2014

Journal of Mineralogical and Petrological Sciences

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We observed the breakdown of natural garnet in a high-pressure experiment (0.85 GPa and 1100°C for 2 days) using a piston-cylinder apparatus. Two different types of kelyphites were formed: (1) isochemical and (2) metasomatic. The isochemical kelyphite was composed of orthopyroxene + spinel + plagioclase, whereas the metasomatic one, having a composition altered significantly from the original garnet, was composed of olivine + spinel + plagioclase. These synthetic kelyphites were studied and characterized using EPMA, SEM, EBSD, and TEM and were shown to have many microstructural features as well as their mineral assemblages in common with observed natural kelyphites. The kelyphitization was very heterogeneous and local and was apparently controlled by grain surfaces and intra-grain cracks in garnet. The metasomatic kelyphite apparently formed by a reaction between garnet and aqueous fluids that may have been introduced from outside the platinum capsule through holes accidentally made in the capsule.

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Two-pyroxene thermobarometry with new experimental data in the system CaO-MgO-Al2O3-SiO2

Cited by 220 publications

References 21 publications

Mineral chemistry of volcanic sequences from Hole 917A, southeast Greenland Margin

Mineral chemistry of volcanic sequences from Hole 917A, southeast Greenland Margin

Geochemical and Sr–Nd–Pb isotopic compositions of lithospheric mantle: Spinel lherzolites in alkaline basalts from the northwestern Ethiopian plateau

Experimental synthesis of isochemical kelyphite — a preliminary report

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