The Late Carboniferous Khuhu Davaa ophiolite in northeastern Mongolia: Implications for the tectonic evolution of the Mongol–Okhotsk Ocean

Abstract

The newly discovered Khuhu Davaa ophiolite is located in the Adaatsag suture zone, which marks the closure of the Mongol–Okhotsk Ocean in northeastern Mongolia. In this paper, we present new geochemical and SIMS zircon U–Pb data for the ophiolite to provide some constraints on the tectonic evolution of the Mongol–Okhotsk orogenic belt. Metagabbro and plagiogranite samples from the ophiolite yielded SIMS zircon U–Pb ages of 321 ± 4 Ma and 314 ± 3 Ma, respectively, which are interpreted to represent the formation age of the ophiolite. These data suggest that the Carboniferous Khuhu Davaa ophiolite is likely related to the contemporaneous Adaatsag ophiolite to the southwest, defining the suture zone of the Mongol–Okhotsk Ocean in northeastern Mongolia. Tholeiitic basalt samples from the ophiolite show N‐MORB and E‐MORB geochemical affinities but are enriched in Ba, Pb, and Sr, which may reflect an input of subduction‐related fluids. Metagabbro samples exhibit HSFE depletion and LILE enrichment, which are diagnostic geochemical features of arc magmatism. Plagiogranites with low TiO2 contents appear to have formed through partial melting rather than fractional crystallization of a mafic crust in the subduction zone environment. Thus, we suggest that the Khuhu Davaa ophiolite resulted from generation of oceanic crust during the closure of the Mongol–Okhotsk Ocean and documents the initiation of subduction during the Late Carboniferous in northeastern Mongolia.

First Paleomagnetic Result From the Early Permian Volcanic Rocks in Northeastern Mongolia: Evolutional Implication for the Paleo‐Asian Ocean and the Mongol‐Okhotsk Ocean

“…The western part of the Mongol-Okhotsk Belt recorded its early stage evolution, where Devonian and Carboniferous clastic turbidite deposits are widely distributed (Zonenshain et al, 1990). Meanwhile, two ophiolitic mélanges with zircon U-Pb ages of 325-314 Ma have been reported from the Adaatsag and Khuhu Davaa regions in central Mongolia, representing remnants of the Mongol-Okhotsk oceanic crust (Tomurtogoo et al, 2005;Zhu et al, 2018). By reviewing geological and geochemical studies on the Late Paleozoic-Mesozoic magmatic rocks on the northern side of the Mongol-Okhotsk suture zone, Donskaya et al 2013suggested that the northward Mongol-Okhotsk oceanic subduction began in the Devonian and reached its climax in the Permian-Triassic.…”

Late Triassic initial closure of the Mongol-Okhotsk Ocean in the western segment: Constraints from sedimentological, detrital zircon ages and paleomagnetic evidence

“…Zircon U-Pb dating results revealed their formation in the ages of 325-314 Ma, indicating the Late Carboniferous formation of the oceanic crust (Fig. 2; Tomurtogoo et al, 2005;Zhu et al, 2018). The late Permian to early Triassic fossiliferous marine sediments and cherts within the suture in northeastern Mongolia indicate the existence of the MOO during these periods (Zonenshain et al, 1990).…”

“…2; Kashiwagi et al, 2004;Kurihara et al, 2009). Two ophiolite assemblages, namely the Adaatsag ophiolite and the Khuhu Davaa ophiolite, have been identified from central and northeastern Mongolia that are composed of cherts, gabbros, metabasalts and ultramafic rocks, with greenschists and gabbro-amphibolites as matrix (Tomurtogoo et al, 2005;Zhu et al, 2018). Zircon U-Pb dating results revealed their formation in the ages of 325-314 Ma, indicating the Late Carboniferous formation of the oceanic crust (Fig.…”

Age, petrogenesis, and tectonic implications of the late Permian magmatic rocks in the Middle Gobi volcanoplutonic Belt, Mongolia

“…The Mongol-Okhotsk suture zone is marked by the ca. 325-314 Ma Adaatsag-Khukhu Davaa ophiolites (Tomurtogoo et al, 2005;Zhu et al, 2018) (Figures 1 and 2). The MOO opened in late Ordovician-early Silurian times, possibly as a back-arc basin on the northern (in present coordinates) active margin of the Paleo-Asian Ocean near the Central Mongolia-Erguna block (Bussien et al, 2011;Miao et al, 2020;Winkler et al, 2020).…”