Triassic alkaline magmatism of the Hawasina Nappes: Post-breakup melting of the Oman lithospheric mantle modified by the Permian Neotethyan Plume

详细信息    查看全文

• 作者：Fran&#xe7 ; ois Chauvet^a ; ^b ; ^{francois.chauvet@univ-nantes.fr} ; Henriette Lapierre^b ; Ren&#xe9 ; C. Maury^c ; Delphine Bosch^d ; Christophe Basile^b ; Joseph Cotten^c ; Pierre Brunet^e ; Sylvain Campillo^b
• 关键词：Neotethys ; Passive margin ; Post-breakup magmatism ; Triassic ; Hawasina ; Oman Mountains
• 刊名：Lithos
• 出版年：2011
• 出版时间：February 2011
• 年：2011
• 卷：122
• 期：1-2
• 页码：122-136
• 全文大小：2196 K

文摘

Middle to Late Triassic lavas were sampled within three tectonostratigraphic groups of the Hawasina Nappes in the Oman Mountains. They are predominantly alkali basalts and trachybasalts, associated with minor sub-alkaline basalts, trachyandesites, trachytes and rhyolites. Their major, trace elements and Nd–Pb isotopic compositions are very similar to those of the Permian plume-related high-Ti basalts which also occur in the Hawasina Nappes. The Triassic lavas derive from low-degree melting of an enriched OIB-type mantle source, characterized by εNd_i = 0.3–5.3 and (²⁰⁶Pb/²⁰⁴Pb)_i = 16.96–19.31 (for t = 230 My). With time, melting depths decreased from the garnet + spinel to the spinel lherzolite facies and the degree of melting increased. The oldest are distinguished from the others by unradiogenic Nd and Pb signatures, with εNd_i = − 4.5 to − 1.2 and (²⁰⁶Pb/²⁰⁴Pb)_i = 16.35–17.08, which we attribute to their contamination by Arabo-Nubian lower crust. The lavas likely derived from the Oman lithospheric mantle, the original DMM-HIMU signature of which was overprinted during its pervasive metasomatism by the Permian plume-related melts. We suggest that these lavas were emplaced during post-breakup decompression-triggered melting in the Middle Triassic during global kinematic reorganization of the Tethyan realm.