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Petrography, mineralogy, and geochemistry of the Hemrin Basalt, Northern Iraq: Implications for petrogenesis and geotectonics
Tekijät: Kettanah Yawooz A., Abdulrahman Alan S., Ismail Sabah A., MacDonald Daniel J., Al Humadi Heider
Kustantaja: Elsevier BV
Julkaisuvuosi: 2021
Journal: Lithos
Artikkelin numero: 106109
Vuosikerta: 390-391
eISSN: 1872-6143
DOI: https://doi.org/10.1016/j.lithos.2021.106109
Verkko-osoite: https://www.sciencedirect.com/science/article/pii/S0024493721001456
Tiivistelmä
The studied Hemrin Basalt (HB) was previously mis-identified and called burnt hills. The HB is studied petro-graphically and geochemically as constraints for its provenance and geotectonics. The immobile trace elementplot of Zr/TiO2–Nb/Y as well as mineralogy, textures and hand specimen appearance indicate that the studiedrocks are basalts. This basalt occurs as surficial thin layer capping few hills along a NW/SE oriented directionwithin the Injana Formation in the Low-Folded Tectonic Zone, which is not related and far from the ophiolitesof northeastern Iraq. It consists dominantly of diopside, labradorite and volcanic glass, and many accessory andsecondary vesicle-filling minerals (amygdules). The basalt is veryfine-grained with a massive and vesicular/amygdaloidal structures, and sub-ophitic as well as very rare and unusual textures, calledfirework and featheryin this study which are very similar to those of lunar basalts. The large ion lithophile elements (LILE) are enriched4.8 times relative to the highfield strength elements (HFSE), indicated from the MORB-normalized diagram formajor and trace elements. The average content of rare earth elements (REE) in HB is 140 ppm with 10.6 timesenrichment of LREE relative to HREE which is reflected in their chondrite-normalized diagram having a negativeslope of 7.6 and a small Eu-anomaly of 0.7. The (La/Yb)n–La plot showed that the source magma was fractionallycrystallized; whereas, the immobile trace element ratios and elemental values such as Nb/U, Ce/Pb, Nb/La, LREE/HREE, LILE/HFSE, Zr, Hf, Nb, and Ta indicated that source magma for HB was contaminated while rising throughthe Arabian continental crust. Many major, immobile trace and REE element discriminating diagrams showedthat the studied rocks are high-K calc-alkaline basalts formed as a continental volcanic arc under orogenic con-vergent tectonic conditions because of the continent-continent collision between the Arabian and Turkish/Iranian plates. The surficial HB and the surrounding calc-alkaline tuffs are probably related and formed by thesame volcanic eruption during Quaternary period, <0.5 Ma ago. The source of HB is most probably a hot spot vol-cano erupted in the area close to the studied hills, ejecting large amounts of volcanic ash which deposited the tuffbeds and the associated bentonites in the surroundings, and culminated by a basalticflow which formed the HB.
© 2021 Published by Elsevier B.V.
The studied Hemrin Basalt (HB) was previously mis-identified and called burnt hills. The HB is studied petro-graphically and geochemically as constraints for its provenance and geotectonics. The immobile trace elementplot of Zr/TiO2–Nb/Y as well as mineralogy, textures and hand specimen appearance indicate that the studiedrocks are basalts. This basalt occurs as surficial thin layer capping few hills along a NW/SE oriented directionwithin the Injana Formation in the Low-Folded Tectonic Zone, which is not related and far from the ophiolitesof northeastern Iraq. It consists dominantly of diopside, labradorite and volcanic glass, and many accessory andsecondary vesicle-filling minerals (amygdules). The basalt is veryfine-grained with a massive and vesicular/amygdaloidal structures, and sub-ophitic as well as very rare and unusual textures, calledfirework and featheryin this study which are very similar to those of lunar basalts. The large ion lithophile elements (LILE) are enriched4.8 times relative to the highfield strength elements (HFSE), indicated from the MORB-normalized diagram formajor and trace elements. The average content of rare earth elements (REE) in HB is 140 ppm with 10.6 timesenrichment of LREE relative to HREE which is reflected in their chondrite-normalized diagram having a negativeslope of 7.6 and a small Eu-anomaly of 0.7. The (La/Yb)n–La plot showed that the source magma was fractionallycrystallized; whereas, the immobile trace element ratios and elemental values such as Nb/U, Ce/Pb, Nb/La, LREE/HREE, LILE/HFSE, Zr, Hf, Nb, and Ta indicated that source magma for HB was contaminated while rising throughthe Arabian continental crust. Many major, immobile trace and REE element discriminating diagrams showedthat the studied rocks are high-K calc-alkaline basalts formed as a continental volcanic arc under orogenic con-vergent tectonic conditions because of the continent-continent collision between the Arabian and Turkish/Iranian plates. The surficial HB and the surrounding calc-alkaline tuffs are probably related and formed by thesame volcanic eruption during Quaternary period, <0.5 Ma ago. The source of HB is most probably a hot spot vol-cano erupted in the area close to the studied hills, ejecting large amounts of volcanic ash which deposited the tuffbeds and the associated bentonites in the surroundings, and culminated by a basalticflow which formed the HB.
© 2021 Published by Elsevier B.V.
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