Refined chronology of late Quaternary eruptions at Harrat Khaybar, Saudi Arabia, with implications for magma dynamics and regional volcanic history.
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| Title: | Refined chronology of late Quaternary eruptions at Harrat Khaybar, Saudi Arabia, with implications for magma dynamics and regional volcanic history. |
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| Authors: | Alohali, Abdullah1,2 alohalia@oregonstate.edu, de Silva, Shanaka1, de León, Alejandro Cisneros1,3, Lewis, Charles1, Schmitt, Axel K.4, Danišík, Martin4, Stelten, Mark E.5, Mukhopadhyay, Sujoy6, Duncan, Robert1, Ramos, Frank C.7 |
| Source: | Geological Society of America Bulletin. Mar2026, Vol. 138 Issue 3/4, p1729-1748. 20p. |
| Subject Terms: | *Volcanic eruptions, *Volcanic fields, *Volcanic hazard analysis, *Uranium-lead dating, *Geological time scales, *Magmatism |
| Geographic Terms: | Saudi Arabia |
| Abstract: | Determining accurate and precise ages for Quaternary volcanic centers is essential for reconstructing volcanic field histories, understanding magmatic processes, and assessing potential hazards or risk. Harrat Khaybar, western Saudi Arabia, is one of the youngest and potentially most active volcanic fields on the Arabian plate, has been active since ca. 1.7 Ma, and is characterized by a spectrum of rock compositions ranging from predominantly alkalic basalt to trachyte and comendite. Previous work in Harrat Khaybar utilizing 40Ar/39Ar incremental heating geochronology to constrain morphological preservation and superpositional relationships bracketed the volcanic activity into broad age groups in intervals of ~150 k.y., and the youngest and most compositionally evolved volcanoes, including Jabal Abyad, Jabal Bayda, and Jabal Qidr, were assigned to the age groups between ca. 300 ka and present. Herein, we establish a detailed chronology of prehistoric silicic and historical basaltic eruptions at central Harrat Khaybar using four independent eruption age determination techniques: zircon double-dating (ZDD), which combines 238U-230Th disequilibrium or U-Pb with (U-Th)/He dating; zircon U-Pb dating; cosmogenic ³He dating; and cosmogenic 36Cl geochronology. These were employed to accurately date six volcanic centers, including the comenditic Jabal Abyad, Jabal Bayda, Jabal Ibayl, and Jabal Alhayyirah, the trachytic Jabal Aluthmor, and the basaltic Jabal Qidr. Additionally, our previously published 40Ar/39Ar ages have been recalculated using isochron intercept (nonatmospheric) 40Ar/36Ar for the trapped Ar component. Our new results reveal that zircon rims from Jabal Abyad and Jabal Bayda define isochron 238U-230Th crystallization ages of 125 ± 4 ka and 144 ± 6 ka, concordant with ZDD eruption ages of 132 ± 4 ka and 149 ± 5 ka, respectively. Zircon U-Pb crystallization and (U-Th)/He eruption ages from Jabal Alhayyirah are concordant at 471 ± 14 ka and 458 ± 18 ka, respectively. Finally, zircons from the nearby Jabal Ibayl yield a U-Pb weighted mean crystallization age of 566 ± 16 ka concordant with the corresponding (U-Th)/He eruption age of 554 ± 12 ka, both of which are notably older than the previously proposed eruption ages of 300–150 ka. Recalculations of published 40Ar/39Ar ages for the youngest volcanoes at central Harrat Khaybar are now in excellent agreement with new geochronological data.Determining accurate and precise ages for Quaternary volcanic centers is essential for reconstructing volcanic field histories, understanding magmatic processes, and assessing potential hazards or risk. Harrat Khaybar, western Saudi Arabia, is one of the youngest and potentially most active volcanic fields on the Arabian plate, has been active since ca. 1.7 Ma, and is characterized by a spectrum of rock compositions ranging from predominantly alkalic basalt to trachyte and comendite. Previous work in Harrat Khaybar utilizing 40Ar/39Ar incremental heating geochronology to constrain morphological preservation and superpositional relationships bracketed the volcanic activity into broad age groups in intervals of ~150 k.y., and the youngest and most compositionally evolved volcanoes, including Jabal Abyad, Jabal Bayda, and Jabal Qidr, were assigned to the age groups between ca. 300 ka and present. Herein, we establish a detailed chronology of prehistoric silicic and historical basaltic eruptions at central Harrat Khaybar using four independent eruption age determination techniques: zircon double-dating (ZDD), which combines 238U-230Th disequilibrium or U-Pb with (U-Th)/He dating; zircon U-Pb dating; cosmogenic 3He dating; and cosmogenic 36Cl geochronology. These were employed to accurately date six volcanic centers, including the comenditic Jabal Abyad, Jabal Bayda, Jabal Ibayl, and Jabal Alhayyirah, the trachytic Jabal Aluthmor, and the basaltic Jabal Qidr. Additionally, our previously published 40Ar/39Ar ages have been recalculated using isochron intercept (nonatmospheric) 40Ar/36Ar for the trapped Ar component. Our new results reveal that zircon rims from Jabal Abyad and Jabal Bayda define isochron 238U-230Th crystallization ages of 125 ± 4 ka and 144 ± 6 ka, concordant with ZDD eruption ages of 132 ± 4 ka and 149 ± 5 ka, respectively. Zircon U-Pb crystallization and (U-Th)/He eruption ages from Jabal Alhayyirah are concordant at 471 ± 14 ka and 458 ± 18 ka, respectively. Finally, zircons from the nearby Jabal Ibayl yield a U-Pb weighted mean crystallization age of 566 ± 16 ka concordant with the corresponding (U-Th)/He eruption age of 554 ± 12 ka, both of which are notably older than the previously proposed eruption ages of 300–150 ka. Recalculations of published 40Ar/39Ar ages for the youngest volcanoes at central Harrat Khaybar are now in excellent agreement with new geochronological data. Our new age data reveal several new insights into the development of Harrat Khaybar. It is now clear that the comenditic eruptions do not belong to the same eruptive phase and indicate an extended history during which comendites have episodically punctuated the basaltic volcanism since at least 600 ka. The data indicate that Jabal Ibayl and Jabal Alhayyirah represent separate older volcanic events, whereas the younger Jabal Abyad and Jabal Bayda volcanoes appear to be coeval, and their spatial proximity implies that they share a magmatic lineage and maybe a common plumbing system. Zircon age spectra of the comendites reveal obvious xenocrysts and antecrysts indicating assimilation of basement and plutonic progenitors, but otherwise they define broad unimodal populations of crystallization ages that overlap within error with the respective eruption ages. We interpret this to indicate that zircon crystallization continued up to the time of eruption. The cosmogenic ages of Jabal Aluthmor and Jabal Qidr reveal that these centers erupted as recently as ca. 2000 and 760 years ago, respectively. Broadly coeval young silicic and basaltic eruptions at northern Harrat Rahat, the harrat immediately south of Harrat Khaybar, may imply a shared geodynamic forcing between the two adjacent volcanic fields. [ABSTRACT FROM AUTHOR] |
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| Items | – Name: Title Label: Title Group: Ti Data: Refined chronology of late Quaternary eruptions at Harrat Khaybar, Saudi Arabia, with implications for magma dynamics and regional volcanic history. – Name: Author Label: Authors Group: Au Data: <searchLink fieldCode="AR" term="%22Alohali%2C+Abdullah%22">Alohali, Abdullah</searchLink><relatesTo>1,2</relatesTo><i> alohalia@oregonstate.edu</i><br /><searchLink fieldCode="AR" term="%22de+Silva%2C+Shanaka%22">de Silva, Shanaka</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22de+León%2C+Alejandro+Cisneros%22">de León, Alejandro Cisneros</searchLink><relatesTo>1,3</relatesTo><br /><searchLink fieldCode="AR" term="%22Lewis%2C+Charles%22">Lewis, Charles</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Schmitt%2C+Axel+K%2E%22">Schmitt, Axel K.</searchLink><relatesTo>4</relatesTo><br /><searchLink fieldCode="AR" term="%22Danišík%2C+Martin%22">Danišík, Martin</searchLink><relatesTo>4</relatesTo><br /><searchLink fieldCode="AR" term="%22Stelten%2C+Mark+E%2E%22">Stelten, Mark E.</searchLink><relatesTo>5</relatesTo><br /><searchLink fieldCode="AR" term="%22Mukhopadhyay%2C+Sujoy%22">Mukhopadhyay, Sujoy</searchLink><relatesTo>6</relatesTo><br /><searchLink fieldCode="AR" term="%22Duncan%2C+Robert%22">Duncan, Robert</searchLink><relatesTo>1</relatesTo><br /><searchLink fieldCode="AR" term="%22Ramos%2C+Frank+C%2E%22">Ramos, Frank C.</searchLink><relatesTo>7</relatesTo> – Name: TitleSource Label: Source Group: Src Data: <searchLink fieldCode="JN" term="%22Geological+Society+of+America+Bulletin%22">Geological Society of America Bulletin</searchLink>. Mar2026, Vol. 138 Issue 3/4, p1729-1748. 20p. – Name: Subject Label: Subject Terms Group: Su Data: *<searchLink fieldCode="DE" term="%22Volcanic+eruptions%22">Volcanic eruptions</searchLink><br />*<searchLink fieldCode="DE" term="%22Volcanic+fields%22">Volcanic fields</searchLink><br />*<searchLink fieldCode="DE" term="%22Volcanic+hazard+analysis%22">Volcanic hazard analysis</searchLink><br />*<searchLink fieldCode="DE" term="%22Uranium-lead+dating%22">Uranium-lead dating</searchLink><br />*<searchLink fieldCode="DE" term="%22Geological+time+scales%22">Geological time scales</searchLink><br />*<searchLink fieldCode="DE" term="%22Magmatism%22">Magmatism</searchLink> – Name: SubjectGeographic Label: Geographic Terms Group: Su Data: <searchLink fieldCode="DE" term="%22Saudi+Arabia%22">Saudi Arabia</searchLink> – Name: Abstract Label: Abstract Group: Ab Data: Determining accurate and precise ages for Quaternary volcanic centers is essential for reconstructing volcanic field histories, understanding magmatic processes, and assessing potential hazards or risk. Harrat Khaybar, western Saudi Arabia, is one of the youngest and potentially most active volcanic fields on the Arabian plate, has been active since ca. 1.7 Ma, and is characterized by a spectrum of rock compositions ranging from predominantly alkalic basalt to trachyte and comendite. Previous work in Harrat Khaybar utilizing 40Ar/39Ar incremental heating geochronology to constrain morphological preservation and superpositional relationships bracketed the volcanic activity into broad age groups in intervals of ~150 k.y., and the youngest and most compositionally evolved volcanoes, including Jabal Abyad, Jabal Bayda, and Jabal Qidr, were assigned to the age groups between ca. 300 ka and present. Herein, we establish a detailed chronology of prehistoric silicic and historical basaltic eruptions at central Harrat Khaybar using four independent eruption age determination techniques: zircon double-dating (ZDD), which combines 238U-230Th disequilibrium or U-Pb with (U-Th)/He dating; zircon U-Pb dating; cosmogenic ³He dating; and cosmogenic 36Cl geochronology. These were employed to accurately date six volcanic centers, including the comenditic Jabal Abyad, Jabal Bayda, Jabal Ibayl, and Jabal Alhayyirah, the trachytic Jabal Aluthmor, and the basaltic Jabal Qidr. Additionally, our previously published 40Ar/39Ar ages have been recalculated using isochron intercept (nonatmospheric) 40Ar/36Ar for the trapped Ar component. Our new results reveal that zircon rims from Jabal Abyad and Jabal Bayda define isochron 238U-230Th crystallization ages of 125 ± 4 ka and 144 ± 6 ka, concordant with ZDD eruption ages of 132 ± 4 ka and 149 ± 5 ka, respectively. Zircon U-Pb crystallization and (U-Th)/He eruption ages from Jabal Alhayyirah are concordant at 471 ± 14 ka and 458 ± 18 ka, respectively. Finally, zircons from the nearby Jabal Ibayl yield a U-Pb weighted mean crystallization age of 566 ± 16 ka concordant with the corresponding (U-Th)/He eruption age of 554 ± 12 ka, both of which are notably older than the previously proposed eruption ages of 300–150 ka. Recalculations of published 40Ar/39Ar ages for the youngest volcanoes at central Harrat Khaybar are now in excellent agreement with new geochronological data.Determining accurate and precise ages for Quaternary volcanic centers is essential for reconstructing volcanic field histories, understanding magmatic processes, and assessing potential hazards or risk. Harrat Khaybar, western Saudi Arabia, is one of the youngest and potentially most active volcanic fields on the Arabian plate, has been active since ca. 1.7 Ma, and is characterized by a spectrum of rock compositions ranging from predominantly alkalic basalt to trachyte and comendite. Previous work in Harrat Khaybar utilizing 40Ar/39Ar incremental heating geochronology to constrain morphological preservation and superpositional relationships bracketed the volcanic activity into broad age groups in intervals of ~150 k.y., and the youngest and most compositionally evolved volcanoes, including Jabal Abyad, Jabal Bayda, and Jabal Qidr, were assigned to the age groups between ca. 300 ka and present. Herein, we establish a detailed chronology of prehistoric silicic and historical basaltic eruptions at central Harrat Khaybar using four independent eruption age determination techniques: zircon double-dating (ZDD), which combines 238U-230Th disequilibrium or U-Pb with (U-Th)/He dating; zircon U-Pb dating; cosmogenic 3He dating; and cosmogenic 36Cl geochronology. These were employed to accurately date six volcanic centers, including the comenditic Jabal Abyad, Jabal Bayda, Jabal Ibayl, and Jabal Alhayyirah, the trachytic Jabal Aluthmor, and the basaltic Jabal Qidr. Additionally, our previously published 40Ar/39Ar ages have been recalculated using isochron intercept (nonatmospheric) 40Ar/36Ar for the trapped Ar component. Our new results reveal that zircon rims from Jabal Abyad and Jabal Bayda define isochron 238U-230Th crystallization ages of 125 ± 4 ka and 144 ± 6 ka, concordant with ZDD eruption ages of 132 ± 4 ka and 149 ± 5 ka, respectively. Zircon U-Pb crystallization and (U-Th)/He eruption ages from Jabal Alhayyirah are concordant at 471 ± 14 ka and 458 ± 18 ka, respectively. Finally, zircons from the nearby Jabal Ibayl yield a U-Pb weighted mean crystallization age of 566 ± 16 ka concordant with the corresponding (U-Th)/He eruption age of 554 ± 12 ka, both of which are notably older than the previously proposed eruption ages of 300–150 ka. Recalculations of published 40Ar/39Ar ages for the youngest volcanoes at central Harrat Khaybar are now in excellent agreement with new geochronological data. Our new age data reveal several new insights into the development of Harrat Khaybar. It is now clear that the comenditic eruptions do not belong to the same eruptive phase and indicate an extended history during which comendites have episodically punctuated the basaltic volcanism since at least 600 ka. The data indicate that Jabal Ibayl and Jabal Alhayyirah represent separate older volcanic events, whereas the younger Jabal Abyad and Jabal Bayda volcanoes appear to be coeval, and their spatial proximity implies that they share a magmatic lineage and maybe a common plumbing system. Zircon age spectra of the comendites reveal obvious xenocrysts and antecrysts indicating assimilation of basement and plutonic progenitors, but otherwise they define broad unimodal populations of crystallization ages that overlap within error with the respective eruption ages. We interpret this to indicate that zircon crystallization continued up to the time of eruption. The cosmogenic ages of Jabal Aluthmor and Jabal Qidr reveal that these centers erupted as recently as ca. 2000 and 760 years ago, respectively. Broadly coeval young silicic and basaltic eruptions at northern Harrat Rahat, the harrat immediately south of Harrat Khaybar, may imply a shared geodynamic forcing between the two adjacent volcanic fields. [ABSTRACT FROM AUTHOR] |
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| RecordInfo | BibRecord: BibEntity: Identifiers: – Type: doi Value: 10.1130/B38611.1 Languages: – Code: eng Text: English PhysicalDescription: Pagination: PageCount: 20 StartPage: 1729 Subjects: – SubjectFull: Volcanic eruptions Type: general – SubjectFull: Volcanic fields Type: general – SubjectFull: Volcanic hazard analysis Type: general – SubjectFull: Uranium-lead dating Type: general – SubjectFull: Geological time scales Type: general – SubjectFull: Magmatism Type: general – SubjectFull: Saudi Arabia Type: general Titles: – TitleFull: Refined chronology of late Quaternary eruptions at Harrat Khaybar, Saudi Arabia, with implications for magma dynamics and regional volcanic history. Type: main BibRelationships: HasContributorRelationships: – PersonEntity: Name: NameFull: Alohali, Abdullah – PersonEntity: Name: NameFull: de Silva, Shanaka – PersonEntity: Name: NameFull: de León, Alejandro Cisneros – PersonEntity: Name: NameFull: Lewis, Charles – PersonEntity: Name: NameFull: Schmitt, Axel K. – PersonEntity: Name: NameFull: Danišík, Martin – PersonEntity: Name: NameFull: Stelten, Mark E. – PersonEntity: Name: NameFull: Mukhopadhyay, Sujoy – PersonEntity: Name: NameFull: Duncan, Robert – PersonEntity: Name: NameFull: Ramos, Frank C. IsPartOfRelationships: – BibEntity: Dates: – D: 01 M: 03 Text: Mar2026 Type: published Y: 2026 Identifiers: – Type: issn-print Value: 00167606 Numbering: – Type: volume Value: 138 – Type: issue Value: 3/4 Titles: – TitleFull: Geological Society of America Bulletin Type: main |
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