Mantle xenolith‐bearing Maastrichtian to Tertiary alkaline magmatism in Oman

Abstract

[1] Mantle xenolith-bearing alkali basalts, basanites and tephrites with 1.5-2 K 2 O and 4-5 wt% Na 2 O occur as small (<100 m) plugs and dikes in the Batain and Haushi-Huqf areas, and WNW of Muscat. Their black color and the common presence of peridotite xenoliths allow a separation from older alkaline rocks and from the ophiolitic extrusive rocks. Two main dike directions, approximately E-W and N-S oriented, are observed. Intrusions seem to occur where these two fault systems intersect. The basalts crosscut the Upper Maastrichtian siliciclastic rocks of the Fayah Formation and the nappe stack of the Eastern Ophiolite Belt of the Batain area. They have not been observed intruding the Tertiary shallow marine carbonates although K-Ar whole rock dating on these lavas yielded Late Eocene 37 ± 1 to 44 ± 1 Ma ages. The rocks are aphyric and fine-grained with microgranular, and less common microtrachytic texture. They contain magmatic olivine

Nature and evolution of the lithospheric mantle beneath the passive margin of East Oman: Evidence from mantle xenoliths sampled by Cenozoic alkaline lavas

“…The upper mantle beneath the North West Al Ashkharah therefore has a similar history than that of the upper mantle beneath Spitsbergen, an other continental rifting area. We tentatively suggest that the partial melting event is an old event while the metasomatic melt is related to the tertiary alkaline magmatic activity of the studied area related to the rifting of the Figure 1: Location map of the studied area (after Gnos and Peters, 2003) Ionov et al (2002); Filled squares in a dark grey field: mantle peridotite xenoliths from Oman (Nasir et al, 2006); Empty squares in a ligth grey field: mantle peridotites from Oman ophiolite from Monnier et al (2006). (Ionov et al, 2002).…”

“…Ionov et al, 2002;Witt-Eickschen et al, 2003 ;Lenoir et al, 2000). Small (< a few cm), mostly lherzolitic, xenoliths have been recently discovered in alkaline dykes and flows emplaced during Cenozoic times along the Oman passive margin facing the Owen basin (see Gnos and Peters, 2003) but they have not been extensively studied yet for their trace element geochemistry. Nasir et al (2006) report on bulk rock trace element analyses but, given the small size of the xenoliths, contamination with the host lava cannot be excluded.…”

Structure of the Offshore Obducted Oman Margin: Emplacement of Semail Ophiolite and Role of Tectonic Inheritance

“…∼65 to 40.4–37.2 (Bartonian, late Eocene): this period is associated with continued extension and lithospheric‐scale readjustments, which could also explain the emplacement of basanites along major faults (i.e., F2, F6; Figures 2 and 8; Gnos et al., 2003; Nasir et al., 2006). The unconformity above unit U3 coincides, according to thermochronological data, with the end of the exhumation of the Jabal Akhdar and Saih Hatat domes (Figure 8b; Hansman et al., 2017).…”

Late Eocene Uplift of the Al Hajar Mountains, Oman, Supported by Stratigraphy and Low‐Temperature Thermochronology

“…Map of Arabia‐Eurasia boundary with anisotropic Pn velocity model redrawn from Al‐Lazki et al (). SSMA, UDMA, and MMA modified from Chiu et al (), CRA modified from Perelló et al (), and basanite localities from Gnos and Peters (). See section 7.4 and Figure 11 for cross section A‐A′.…”