TY - JOUR
T1 - Geochemistry and petrology of Tertiary volcanic rocks and related ultramafic xenoliths from the central and eastern Oman Mountains
AU - Nasir, Sobhi
AU - Al-Sayigh, Abdulrazak
AU - Alharthy, Abdulrahman
AU - Al-Lazki, Ali
N1 - Funding Information:
S. Nasir acknowledges financial support from the German academic exchange service (DAAD). Hans-Joachim Massonne and Thomas Theye are thanked for their help with the microprobe analysis. The authors thank Hugh Rollinson for reading early draft of the manuscript. The authors are grateful for the thorough and constructive reviews of T. Peters, E. Gnos and H. Lapierre.
PY - 2006/9
Y1 - 2006/9
N2 - The Tertiary volcanic rocks of the central and the eastern parts of the Oman Mountains consist mainly of basanites with abundant upper mantle ultramafic xenoliths. The lavas are alkaline (42-43 wt.% SiO2; 3.5-5.5 wt.% Na2O + K2O). They include primitive (11-14 wt.% MgO) features with strong OIB-like geochemical signatures. Trace element and Sr-Nd isotope data for the basanites suggest mixing of melts derived from variable degrees of melting of both garnet- and spinel lherzolite-facies mantle source. The associated xenolith suite consists mainly of spinel and Cr-bearing diopside wehrlite, lherzolite and dunite with predominantly granuloblastic textures. No significant difference in chemistry was found between the basanites and xenoliths from the central and eastern Oman Mountains, which indicate a similar mantle source. Calculated oxygen fugacity indicates equilibration of the xenoliths at - 0.43 to - 2.2 log units above the fayalite-magnetite-quartz (FMQ) buffer. Mantle xenolith equilibration temperatures range from 910-1045 + 50 °C at weakly constrained pressures between 13 and 21 kbar. Xenolith data and geophysical studies indicate that the Moho is located at a depth of ∼ 40 km. A geotherm substantially hotter (90 mW m- 2) than the crust-mantle boundary (45 mW m- 2) is indicated and probably relates to tectonothermal events associated with the local and regional Tertiary magmatism. The petrogenesis of the Omani Tertiary basanites is explained by partial melting of an asthenospheric mantle protolith during an extension phase predating opening of the Gulf of Aden and plume-related alkaline volcanic rocks.
AB - The Tertiary volcanic rocks of the central and the eastern parts of the Oman Mountains consist mainly of basanites with abundant upper mantle ultramafic xenoliths. The lavas are alkaline (42-43 wt.% SiO2; 3.5-5.5 wt.% Na2O + K2O). They include primitive (11-14 wt.% MgO) features with strong OIB-like geochemical signatures. Trace element and Sr-Nd isotope data for the basanites suggest mixing of melts derived from variable degrees of melting of both garnet- and spinel lherzolite-facies mantle source. The associated xenolith suite consists mainly of spinel and Cr-bearing diopside wehrlite, lherzolite and dunite with predominantly granuloblastic textures. No significant difference in chemistry was found between the basanites and xenoliths from the central and eastern Oman Mountains, which indicate a similar mantle source. Calculated oxygen fugacity indicates equilibration of the xenoliths at - 0.43 to - 2.2 log units above the fayalite-magnetite-quartz (FMQ) buffer. Mantle xenolith equilibration temperatures range from 910-1045 + 50 °C at weakly constrained pressures between 13 and 21 kbar. Xenolith data and geophysical studies indicate that the Moho is located at a depth of ∼ 40 km. A geotherm substantially hotter (90 mW m- 2) than the crust-mantle boundary (45 mW m- 2) is indicated and probably relates to tectonothermal events associated with the local and regional Tertiary magmatism. The petrogenesis of the Omani Tertiary basanites is explained by partial melting of an asthenospheric mantle protolith during an extension phase predating opening of the Gulf of Aden and plume-related alkaline volcanic rocks.
KW - Basanite
KW - Extension
KW - Geochemistry
KW - Lithosphere
KW - Mantle plume
KW - Oman Mountains
KW - P-T conditions
KW - Ultramafic xenoliths
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U2 - 10.1016/j.lithos.2006.03.002
DO - 10.1016/j.lithos.2006.03.002
M3 - Article
AN - SCOPUS:33748417760
SN - 0024-4937
VL - 90
SP - 249
EP - 270
JO - Lithos
JF - Lithos
IS - 3-4
ER -