Makran ophiolitic basalts (SE Iran) record Late Cretaceous Neotethys plume-ridge interaction

ABSTRACT

The Makran complex in southeast Iran provides a spectacular subduction-related accretionary complex to understand the mechanism of oceanic accretion and the evolution of subduction zones. In this paper, we present new major and trace element data as well as isotopic compositions of mafic volcanic blocks from the Makran ophiolitic mélange complex (OMC). Our aim is to assess the genesis of these rocks and discuss their implications on the evolution of Neotethys Ocean. These volcanic blocks are composed mainly of basalts with minor trachytes. The Makran lavas are occasionally interlayered with tuff layers. Zircons from these tuffs give U-Pb ages of 95 Ma, which is well in accordance with the reposted microfossil data for the interlayered pelagic limestones with pillow lavas. Makran basalts can be geochemically subdivided into four groups; normal to transitional MORB, enriched-MORB, Plume-type MORB and alkaline (-OIB-like) basalts. The OIB-like pillow lavas are represented by high values of Th/Tb (6.3–7.4) which are higher than other basalts (group 1 = 0.3–0.8; groups 2 = 0.7–1.6; group 3 = 1.58–1.36).¹⁴³Nd/¹⁴⁴Nd_(t) ratios for basalts ranges from 0.51247 to 0.51292, whereas ⁸⁷Sr/⁸⁶Sr_(t) isotopic composition of the OMC lavas varies from 0.704433 to 0.709466. The Pb isotopic composition of the lavas are quite high, ranging from 15.49–15.66 for ²⁰⁷Pb/²⁰⁴Pb_(t), 18.09–19.12 for ²⁰⁶Pb/²⁰⁴Pb_(t) and 37.80–39.23 for ²⁰⁸Pb/²⁰⁴Pb_(t). The chemistry of these rocks suggests that they were formed most likely in an oceanic setting with clear plume-ridge interaction. These rocks can form from partial melting of a highly heterogeneous mantle source, which is extensively metasomatized with deep mantle OIB-type components. We suggest these rocks have been generated in an oceanic ridge with plume-ridge interaction, similar to the Iceland-Reykjanes Ridge, before being fragmented and accreted into the Makran accretionary complex.

Graphical Abstract

KEYWORDS:

• plume-ridge interaction
• mélange
• basalt
• geochemistry
• Makran
• Iran

Article Highlights

• Mafic blocks from ophiolitic Mélange of Makran Complex studied to unravel the petrogenesis of Neo-Tethys ocean crust to the south of Iran.

• Ophiolitic Mélange of Makran Complex preserves evidence of the evolution of Neo-Tethys ocean crust.

• Tectonic setting akin to oceanic crust formed on buoyant seamounts and/or Ridges.

Acknowledgments

We thank Rixiang Zhu, Fuyuan Wu and Sun-Lin Chung for their advice and help in the study of the Tethyan domain research. We appreciate three anonymous reviewers for their constructive and helpful reviews, which significantly improved the manuscript. The authors acknowledge Dr Esmail Karamidehkordi, Director of International Scientific Cooperation Office and Dr Ghasem Nabatian, head of Department of Geology, and other authorities at the University of Zanjan for their logistic assistance. The Strategic Priority Research Program (B) of the Chinese Academy of Sciences (CAS) (XDB18020203), the National Natural Science Foundation of china (91755102, 91855207,41672085, 41822204 and 41472192), the Key Research Program of Frontier Sciences, CAS (QYZDJ-SSW-SYS012) and CAS-TWAS President׳s Fellowship jointly supported this study. This is a contribution to IGCP 662.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary Material

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Additional information

Funding

This work was supported by the The Key Research Program of Frontier Sciences, CAS [QYZDJ-SSW-SYS012];The National Natural Science Foundation of china [91755102, 91855207, 41672085, 41822204 and 41472192];The Strategic Priority Research Program (B) of the Chinese Academy of Sciences (CAS) [XDB18020203], CAS-TWAS President׳s Fellowship for International Students, IGCP 662.