Petrogenesis of arc-related peridotite hosted chromitite deposits in Sikhoran-Soghan mantle section, South Iran: evidence for proto-forearc spreading to boninitic stages
The Soghan-Sikhoran ophiolite in southeast Iran (Outer Zagros Ophiolite Belt) is a remnant of a series of Upper Triassic–Cretaceous supra-subduction zone (SSZ) ophiolites that formed along the Zagros suture zone, which is considered as the southern border of the Neo-Tethyan sea. These SSZ ophiolites...
| Main Authors: | , , , , |
|---|---|
| Format: | Journal article |
| Language: | English |
| Published: |
Elsevier
2021
|
| _version_ | 1811139154882330624 |
|---|---|
| author | Sepidbar, F Khedr, MZ Ghorbani, MR Palin, R Xiao, Y |
| author_facet | Sepidbar, F Khedr, MZ Ghorbani, MR Palin, R Xiao, Y |
| author_sort | Sepidbar, F |
| collection | OXFORD |
| description | The Soghan-Sikhoran ophiolite in southeast Iran (Outer Zagros Ophiolite Belt) is a remnant of a series of Upper Triassic–Cretaceous supra-subduction zone (SSZ) ophiolites that formed along the Zagros suture zone, which is considered as the southern border of the Neo-Tethyan sea. These SSZ ophiolites are older than the Late Cretaceous Zagros ophiolites. The main part of the Soghan-Sikhoran ophiolite comprises layered ultramafic cumulates including dunites, wehrlites, and pyroxenites, and a tectonized mantle section including residual lherzolites, and depleted harzburgites with foliated/discordant dunite lenses. Podiform chromitites are common and are typically surrounded by thin dunitic haloes. Spinels in lherzolite–harzburgite are geochemically characterized by a low Cr# (42.0 to 52.6), and plot in an abyssal peridotite field on geochemical discrimination diagrams, whereas spinel in dunites and high-Cr chromitite spinels (Cr# = 52.4 to 76.4) show geochemical affinities to boninites. Lherzolites and harzburgites have low REE contents and experienced >17 vol% partial melting. The Soghan-Sikhoran ophiolite contains both high Cr# and low Cr# podiform chromitite types. Trace and REE element patterns of Soghan-Sikhoran rocks are similar to those in SSZ peridotites. The studied ophiolites show relatively moderate to high oxygen fugacities (ƒO2), with log units ranging from −0.4 to +0.4 for harzburgites, +0.2 for lherzolites, from − 0.7 to + 2.5 for pyroxenites, from +0.8 to +2.2 for dunites, and from + 0.6 to + 0.8 for chromitites. The moderate to high oxidation state of the studied upper-mantle ophiolitic complexes also suggests a boninitic source in the mantle wedge of the arc setting. The two-pyroxene thermometer yields mean equilibrium temperatures of 879 °C, 895 °C, 912 °C and 912 °C for harzburgites, lherzolites, dunites and pyroxenites, respectively. We therefore interpret that the spinels in the lherzolite-harzburgite crystallized from tholeiitic melt generated due to proto-forearc spreading and formation of the infant arc, whereas high-Cr# spinel in dunites and high-Cr# chromitite crystallized from boninitic melts during the mature arc stage, with an increasing contribution of slab-derived fluids at high ƒO2. |
| first_indexed | 2024-09-25T04:01:35Z |
| format | Journal article |
| id | oxford-uuid:50df3f10-2de8-429e-b615-7b1f23885f9f |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-09-25T04:01:35Z |
| publishDate | 2021 |
| publisher | Elsevier |
| record_format | dspace |
| spelling | oxford-uuid:50df3f10-2de8-429e-b615-7b1f23885f9f2024-04-29T11:24:19ZPetrogenesis of arc-related peridotite hosted chromitite deposits in Sikhoran-Soghan mantle section, South Iran: evidence for proto-forearc spreading to boninitic stagesJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:50df3f10-2de8-429e-b615-7b1f23885f9fEnglishSymplectic ElementsElsevier2021Sepidbar, FKhedr, MZGhorbani, MRPalin, RXiao, YThe Soghan-Sikhoran ophiolite in southeast Iran (Outer Zagros Ophiolite Belt) is a remnant of a series of Upper Triassic–Cretaceous supra-subduction zone (SSZ) ophiolites that formed along the Zagros suture zone, which is considered as the southern border of the Neo-Tethyan sea. These SSZ ophiolites are older than the Late Cretaceous Zagros ophiolites. The main part of the Soghan-Sikhoran ophiolite comprises layered ultramafic cumulates including dunites, wehrlites, and pyroxenites, and a tectonized mantle section including residual lherzolites, and depleted harzburgites with foliated/discordant dunite lenses. Podiform chromitites are common and are typically surrounded by thin dunitic haloes. Spinels in lherzolite–harzburgite are geochemically characterized by a low Cr# (42.0 to 52.6), and plot in an abyssal peridotite field on geochemical discrimination diagrams, whereas spinel in dunites and high-Cr chromitite spinels (Cr# = 52.4 to 76.4) show geochemical affinities to boninites. Lherzolites and harzburgites have low REE contents and experienced >17 vol% partial melting. The Soghan-Sikhoran ophiolite contains both high Cr# and low Cr# podiform chromitite types. Trace and REE element patterns of Soghan-Sikhoran rocks are similar to those in SSZ peridotites. The studied ophiolites show relatively moderate to high oxygen fugacities (ƒO2), with log units ranging from −0.4 to +0.4 for harzburgites, +0.2 for lherzolites, from − 0.7 to + 2.5 for pyroxenites, from +0.8 to +2.2 for dunites, and from + 0.6 to + 0.8 for chromitites. The moderate to high oxidation state of the studied upper-mantle ophiolitic complexes also suggests a boninitic source in the mantle wedge of the arc setting. The two-pyroxene thermometer yields mean equilibrium temperatures of 879 °C, 895 °C, 912 °C and 912 °C for harzburgites, lherzolites, dunites and pyroxenites, respectively. We therefore interpret that the spinels in the lherzolite-harzburgite crystallized from tholeiitic melt generated due to proto-forearc spreading and formation of the infant arc, whereas high-Cr# spinel in dunites and high-Cr# chromitite crystallized from boninitic melts during the mature arc stage, with an increasing contribution of slab-derived fluids at high ƒO2. |
| spellingShingle | Sepidbar, F Khedr, MZ Ghorbani, MR Palin, R Xiao, Y Petrogenesis of arc-related peridotite hosted chromitite deposits in Sikhoran-Soghan mantle section, South Iran: evidence for proto-forearc spreading to boninitic stages |
| title | Petrogenesis of arc-related peridotite hosted chromitite deposits in Sikhoran-Soghan mantle section, South Iran: evidence for proto-forearc spreading to boninitic stages |
| title_full | Petrogenesis of arc-related peridotite hosted chromitite deposits in Sikhoran-Soghan mantle section, South Iran: evidence for proto-forearc spreading to boninitic stages |
| title_fullStr | Petrogenesis of arc-related peridotite hosted chromitite deposits in Sikhoran-Soghan mantle section, South Iran: evidence for proto-forearc spreading to boninitic stages |
| title_full_unstemmed | Petrogenesis of arc-related peridotite hosted chromitite deposits in Sikhoran-Soghan mantle section, South Iran: evidence for proto-forearc spreading to boninitic stages |
| title_short | Petrogenesis of arc-related peridotite hosted chromitite deposits in Sikhoran-Soghan mantle section, South Iran: evidence for proto-forearc spreading to boninitic stages |
| title_sort | petrogenesis of arc related peridotite hosted chromitite deposits in sikhoran soghan mantle section south iran evidence for proto forearc spreading to boninitic stages |
| work_keys_str_mv | AT sepidbarf petrogenesisofarcrelatedperidotitehostedchromititedepositsinsikhoransoghanmantlesectionsouthiranevidenceforprotoforearcspreadingtoboniniticstages AT khedrmz petrogenesisofarcrelatedperidotitehostedchromititedepositsinsikhoransoghanmantlesectionsouthiranevidenceforprotoforearcspreadingtoboniniticstages AT ghorbanimr petrogenesisofarcrelatedperidotitehostedchromititedepositsinsikhoransoghanmantlesectionsouthiranevidenceforprotoforearcspreadingtoboniniticstages AT palinr petrogenesisofarcrelatedperidotitehostedchromititedepositsinsikhoransoghanmantlesectionsouthiranevidenceforprotoforearcspreadingtoboniniticstages AT xiaoy petrogenesisofarcrelatedperidotitehostedchromititedepositsinsikhoransoghanmantlesectionsouthiranevidenceforprotoforearcspreadingtoboniniticstages |