Amphibolites from makran accretionary complex record Permian-Triassic Neo-Tethyan evolution

ABSTRACT

Zircon U-Pb-Hf isotopes, integrated with bulk-rock major, trace element, and isotopic compositions of amphibolites from the Makran ophiolitic mélange complex (OMC), carry implications on the evolution of the Neo-Tethys Ocean. Field and petrographical-geochemical data confirm these amphibolites as products of the metamorphism of a mafic protolith. Zircons from the amphibolites have U-Pb ages of Late Early Permian (273 Ma) to Late Triassic (210 Ma), and their εHf(t) values vary from +6.32 to +15.4. The Makran amphibolites are geochemically similar to transitional- or enriched-MORBs. The 143Nd/144Nd(t) ratios for amphibolites range from 0.51260 to 0.512551, and 87Sr/86Sr(t) from 0.704433 to 0.706244. The Pb-isotope composition of these rocks is radiogenic, ranging from 15.61-15.64 for 207Pb/204Pb(t), 18.98-19.21 for 206Pb/204Pb(t) and 38.88-39.36 for 208Pb/204Pb(t). The isotopic and geochemical signatures of these rocks suggest that they were most likely formed during continental rifting and originated from a relatively enriched mantle source. This is also attested by their high zircon Ce/Ce* ratios. We interpret these amphibolites related to the Permian-Triassic plumes that triggered Gondwana rifting to open the Neo-Tethyan Ocean before metamorphosed, fragmented, and accreted into the Makran accretionary complex probably during Early to Late Cretaceous time.

KEYWORDS:

• Amphibolite
• zircon U-PB
• Gondwana
• Permian
• Makran
• Iran

Highlights

• The amphibolites zircons from the Makran show U-Pb ages from Late Early Permian (273 Ma) to Late Triassic (210 Ma).

• The Makran amphibolites metamorphosed from basaltic protolith.

• Gondwana continental rifting was produce the protolith of Makran amphibolite.

Acknowledgments

The authors acknowledge authorities at the University of Zanjan for their logistic help. We appreciate Professor Emilio Saccani, Kaan Sayit, and one anonymous reviewer for their valuable comments, which significantly improved our manuscript. The National Science Foundation of China (41888101, 41822204, 91755102, 91855207, and 41672085), the Key Research Program of Frontier Sciences, CAS (QYZDJ‐SSW‐SYS012), CAS Project of the China–Pakistan Joint Research Center on Earth Sciences (131551KYSB20200021), the International Affairs and Technological Exchange Center of Iran jointly supported this study. This is a contribution to IGCP 662.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed here

Additional information

Funding

This work was supported by the Key Project of the China–Pakistan Joint Research Center on Earth Sciences [131551KYSB20200021]; The National Science Foundation of China [41888101, 41822204, 91755102, 91855207, and 416720]; and the Key Research Program of Frontier Sciences, CAS [QYZDJ‐SSW‐SYS012]. This is a contribution to IGCP [662]