Detrital chrome spinel evidence for a Neotethyan intra-oceanic island arc collision with India in the Paleocene

Abstract

Models that support a single collision scenario for India and Eurasia are incompatible with the evidence that an intra-oceanic island arc (IOIA) existed within the Neotethyan Ocean. Understanding the spatial and temporal extent of any IOIA is crucial for India-Eurasia collision studies as the entire ocean, including any intraoceanic features, must have been consumed or emplaced prior to continental collision.Here, we review what is known about the Neotethyan IOIA and report evidence from sedimentary successions in NW India and southern Tibet to constrain when and where it was emplaced. We use detrital mineral geochemistry and supporting provenance 2 and age data to identify the source of the sediments and compare the timing of erosion of IOIA-derived material in both regions. Detrital chrome spinels, extracted from distinct sedimentary horizons in southern Tibet (Sangdanlin) and NW India (Ladakh), exhibit similar average geochemical values (TiO 2 = 0.09 and 0.24%, Cr# = 0.66 and 0.68 and Mg# = 0.45 and 0.53, respectively) and supra-subduction zone (SSZ), forearc peridotite signatures. Furthermore, they overlap with in-situ chrome spinels reported from the Spongtang Ophiolite in NW India and the Sangsang Ophiolite in southern Tibet. As with many of the ophiolitic remnants that crop out in and adjacent to the Yarlung-Tsangpo and Indus suture zones (YTSZ and ISZ respectively), the Spongtang and Sangsang ophiolites formed in an IOIA setting. Linking the source of the detrital chrome spinels to those analysed from remnant IOIA massifs in the YTSZ and ISZ is strong evidence for the emplacement of the IOIA onto the Indian margin.The timing of the IOIA collision with India is constrained by the depositional ages of the chrome spinel-bearing sediments to the end of the Paleocene (Thanetian) in southern Tibet and the Early Eocene in NW India. This indirectly provides a maximum age constraint of Late Paleocene-Early Eocene for intercontinental collision between India and Eurasia. Additionally, this study highlights the importance of targeting distinct sedimentary horizons in collision zones to find evidence for discrete tectonic events that may be obfuscated by later collisions.

Tectonic Implications of Detrital Zircon Ages From Lesser Himalayan Mesozoic‐Cenozoic Strata, Pakistan

“…Late Cretaceous marks collision between the KLA and the KB (Burg, 2011). During this time the emplacement of the ophiolites at the northern margin of India has been documented along the strike such as Muslimbagh-Waziristan-Dargai ophiolites in Pakistan, Spontang and Nidar ophiolites in Northwest India, and ophiolites of Central Tibet (Baxter et al, 2016;Brookfield & Reynolds, 1981;Corfield et al, 1999;Ding et al, 2005;Green et al, 2008;Searle et al, 1987;Treloar & Izatt, 1993). Therefore, we consider the possibility that this angular unconformity might be the result of ophiolite emplacement along the northern margin of the Indian plate (Figures 9b and 9c).…”

Discovery of Vestige Sedimentary Archives of the India‐Asia Collision in the Eastern Yarlung Zangbo Suture Zone

“…For the detrital zircons of this age interval from the Xigaze forearc and syncollisional basins in north of YZSZ, researchers have reached a consensus that they had been derived from the Gangdese arc/Asian Trans‐Himalaya (e.g., Aitchison et al, 2011; An et al, 2014; Hu, Wang et al, 2016; Orme et al, 2015; Wu et al, 2010). For the coeval zircons from the Cretaceous‐Paleogene strata/mélange within and south of the YZSZ, lots of geologists interpreted they have come from the Gangdese arc (e.g., Cai et al, 2011; DeCelles et al, 2014; Fu et al, 2018; Hu et al, 2012, 2015; Najman et al, 2010; Wu et al, 2014) and a few supposed they possibly came from an intraoceanic island arc and/or ophiolites preserved in the YZSZ (e.g., Aitchison et al, 2007, 2011; Baxter et al, 2016; Bouilhol et al, 2013).…”

“…However, abundant detritus of felsic volcanic, recycled sedimentary rocks, and quartz grains in the Sangdanlin Fm and Zheya Fm, Zongzhuo Fm, and Jiachala Fm from the central YZSZ and in the Pengqu Fm from the Tethys Himalaya (e.g., DeCelles et al, 2014; Fu et al, 2018; Hu et al, 2012, 2015; Li et al, 2005; Wang et al, 2011) demonstrate that the majority of the detritus was most likely eroded from the intermediate to felsic upper crust, perhaps few from the mafic‐ultramafic ophiolites (Aitchison et al, 2007; Baxter et al, 2016). Hafnium isotopic compositions of the Mesozoic detrital zircons from the Paleogene strata of the central South Tibet are both positive and negative ε Hf ( t ) values (Figure 11b), indicating two different component sources.…”

Chapter 1 Introduction to the geology of Myanmar

“…These tectonic processes associated with semi-continuous sedimentation, magmatic and metamorphic events have made the Myanmar Region highly prospective for metalliferous ores and gem deposits . Molnar & Tapponnier (1975) proposed that the collision of the Indian continental crust with the southern margin of Eurasia since Cretaceous (Baxter et al 2016; references therein) resulted in the eastwards extrusion of continental blocks along major strike-slip transcurrent faults, together with the clockwise rotation of the whole of Southeast Asia. Two of the major strike-slip faults, the Papun (Mae Ping) Fault Zone and the Three Pagodas Fault Zone in Mon and Kayin states, extend from the Sagaing Fault southeastwards into Thailand.…”