Origin and tectonic evolution of the NE basement of Oman: a window into the Neoproterozoic accretionary growth of India?

Abstract

The Omani basement is located spatially distant from the dominantly juvenile Arabian–Nubian Shield (ANS) to its west, and its relationship to the amalgamation of those arc terranes has yet to be properly constrained. The Jebel Ja'alan (NE Oman) basement inlier provides an excellent opportunity to better understand the Neoproterozoic tectonic geography of Oman and its relationship to the ANS. To understand the origin of this basement inlier, we present new radiogenic isotopic data from igneous bodies in Jebel Ja'alan. U–Pb and 40Ar/39Ar geochronological data are used to constrain the timing of magmatism and metamorphism in the jebel. Positive εHf and εNd values indicate a juvenile origin for the igneous lithologies. Phase equilibria modelling is used to constrain the metamorphic conditions recorded by basement. Pressure–temperature (P–T) pseudosections show that basement schists followed a clockwise P–T path, reaching peak metamorphic conditions of c. 650–700°C at 4–7.5 kbar, corresponding to a thermal gradient of c. 90–160°C/kbar. From the calculated thermal gradient, in conjunction with collected trace-element data, we interpret that the Jebel Ja'alan basement formed in an arc environment. Geochronological data indicate that this juvenile arc formed during Tonian time and is older than basement further west in Oman. We argue that the difference in timing is related to westwards arc accretion and migration, which implies that the Omani basement represents its own tectonic domain separate to the ANS and may be the leading edge of the Neoproterozoic accretionary margin of India.

Evolving Marginal Terranes During Neoproterozoic Supercontinent Reorganization: Constraints From the Bemarivo Domain in Northern Madagascar

“…Together this implies that the crustal assimilate incorporated into magmatic rocks of the Bobakindro Terrane was not significantly older than c. 720 Ma. This supports a model where the Bobakindro Terrane formed on a rolled‐back crustal remnant of slightly older crust, possibly from south China, Malani or Oman (Alessio et al, ).…”

“…R scripts to produce plots are provided in Supplementary File C. Data sourced from the following: Alessio et al (), Archibald et al (), Ashwal et al (), Blades et al (), Huang et al (), Long et al (), Morag et al (), Qi et al (), Robinson et al (), Wang et al (), Wang et al (), Zhao et al (), Zheng et al (), Zheng et al (), and Zhou et al ().…”

Neoproterozoic Nafun Group Sediments from Oman Affected by an Active Continental Margin

“…A similar view is that the subsidence was caused by the tectonic loading and development of a foreland basin [21]. Alessio et al [71] studied the igneous samples from Jebel Ja'alan (North eastern Oman) and concluded that they were formed in an arc environment during the Tonian.…”

“…This basin would be affected by a Neoproterozoic volcanic belt [72], as well as multiple phases of volcanic activity in Mirbat [73] and basaltic to rhyolitic dykes in Al Hallaniyah Islands [74]. However, there is still uncertainty about the full geodynamic setting and interrelationship between eastern Oman and the rest of adjacent tectonic plates, such as the Iran plate [75] or India plate [71,76,77]. uncertainty about the full geodynamic setting and interrelationship between eastern Oman and the rest of adjacent tectonic plates, such as the Iran plate [75] or India plate [71,76,77].…”

Extending full-plate tectonic models into deep time: Linking the Neoproterozoic and the Phanerozoic

“…Alessio et al (2018) andArmistead et al (2019), the northwest margin of India is here interpretedas an extensive Stenian-Tonian accretionary margin that extends as far as the Omani basement and northernmost Madagascar. The pre-Ediacaran basement rocks in Rajasthan and Pakistan share similarities with those of Oman.…”