Publication: Mineralogical characterization of peridotite xenoliths from the Los Tormos volcano (Calatrava volcanic field)
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2018
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Sociedad Geológica de España
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Abstract
Los xenolitos de peridotitas del volcán Los Tormos (campo volcánico de Calatrava) proporcionan información valiosa sobre el manto litosférico del centro de España. Se estima que provienen de profundidades de 35-50 km (10-15.2 kbar), equilibrados a temperaturas de 961-1185 ºC, en el campo de estabilidad de peridotitas con espinela. Los modelos de fusión obtenidos a partir de la composición química de los minerales primarios de la peridotita (ortopiroxeno, clinopiroxeno y espinela) muestran un bajo grado de fusión parcial (hasta un 10%), aunque una harzburgita indica un mayor grado de fusión (cerca del 15%). El xenolito de wehrlita se interpreta como un tipo metasomatizado debido a la posible interacción con fundidos alcalinos subsaturados en sílice que eemplazarían el ortopiroxeno primario de la lherzolita. La similitud entre las presiones estimadas para el equilibrio mineral de la peridotita y la cristalización de megacristales/fenocristales de clinopiroxeno en la nefelinita sugiere la formación de cámaras magmáticas mantélicas.
Peridotite xenoliths from the Los Tormos volcano Calatrava volcanic field) provide significant information about the lithospheric mantle of Central Iberia. Studied samples are classified as spinel-bearing lherzolite, harzburgite and wehrlite. Chemical composition of olivine and two pyroxenes shows similar Mg# ranges, providing evidence of mineral equilibrium. Geothermobarometic estimates give depths in the spinel peridotite stability field (35-50 km, 10-15.2 kbar), and temperatures of 961-1185 °C. Major element mineral melting models in the lherzolite xenoliths record a low partial melting degree (up to 10%) although one harzburgite indicates a higher degree of melting (about 15%). The wehrlite sample could result from metasomatism by interaction with alkaline silica-undersaturated melts that replaced primary lherzolite orthopyroxene. Similar estimated pressures for peridotite mineral equilibration and for clinopyroxene megacryst/phenocryst crystallization in the host nephelinite suggest the formation of mantle magma chambers, where alkaline magmas entrained megacrysts (cumulates) and peridotite wall-rocks.
Peridotite xenoliths from the Los Tormos volcano Calatrava volcanic field) provide significant information about the lithospheric mantle of Central Iberia. Studied samples are classified as spinel-bearing lherzolite, harzburgite and wehrlite. Chemical composition of olivine and two pyroxenes shows similar Mg# ranges, providing evidence of mineral equilibrium. Geothermobarometic estimates give depths in the spinel peridotite stability field (35-50 km, 10-15.2 kbar), and temperatures of 961-1185 °C. Major element mineral melting models in the lherzolite xenoliths record a low partial melting degree (up to 10%) although one harzburgite indicates a higher degree of melting (about 15%). The wehrlite sample could result from metasomatism by interaction with alkaline silica-undersaturated melts that replaced primary lherzolite orthopyroxene. Similar estimated pressures for peridotite mineral equilibration and for clinopyroxene megacryst/phenocryst crystallization in the host nephelinite suggest the formation of mantle magma chambers, where alkaline magmas entrained megacrysts (cumulates) and peridotite wall-rocks.