Contrasting P-T conditions recorded in ultramafic high-pressure rocks from the Variscan Schwarzwald (F.R.G.)

• Verfasst von: Kalt, Angelika [VerfasserIn]
• Verfasst von: Altherr, Rainer [VerfasserIn]
• Verfasst von: Hanel, Michael [VerfasserIn]
• Titel: Contrasting P-T conditions recorded in ultramafic high-pressure rocks from the Variscan Schwarzwald (F.R.G.)
• Verf.angabe: Angelika Kalt, Rainer Altherr, Michael Hanel
• Jahr: 1995
• Umfang: 16 S.
• Fussnoten: Gesehen am 10.01.2023
• Titel Quelle: Enthalten in: Contributions to mineralogy and petrology
• Ort Quelle: Berlin : Springer, 1947
• Jahr Quelle: 1995
• Band/Heft Quelle: 121(1995), 1, Seite 45-60
• ISSN Quelle: 1432-0967
• DOI: doi:10.1007/s004100050089
• Datenträger: Online-Ressource
• Sprache: eng
• Sach-SW: Contrib Mineral Petrol
• Sach-SW: Garnet Peridotite
• Sach-SW: Moldanubian Zone
• Sach-SW: Olivine
• Sach-SW: Thermobarometric Calculation
• K10plus-PPN: 1830659928

Abstract

This paper presents mineralogical and tex-tural data as well as thermobarometric calculations on ultramafic high-pressure rocks from the Variscan basement of the Schwarzwald (F.R.G.). The rocks form small isolated bodies within low-pressure / high-temperature gneisses and migmatites. The results of this study constrain contrasting P-T evolutions for four garnet-bearing ultramafic high-pressure rocks. Two magnesian garnet-spinal peridotites sampled near the southern margin of the Central Schwarzwald Gneiss Complex (CSGC) were equilibrated at 670-740° C and 1.4-1.8 GPa. These P-T conditions are similar to those recorded by eclogites intercalated in the same basement unit. Two garnet websterites sampled from the northern part of the CSGC have comparatively low Mg/(Mg + Fe) and low Cr and Ni abundances and are interpreted as former cumulates. These rocks most probably experienced an initial high-temperature stage within the spinel peridotite stability field, followed by re-equilibration at 740-850° C/3.2-4.3 GPa and subsequent recrystallization at lower pressures. Further petrologic studies have to reveal whether ultramafic high-pressure rocks of the Schwarzwald can generally be assigned to these two groups which are mainly defined by contrasting peak pressures.