Aulacogen formation in response to opening the ailaoshan ocean: Origin of the qin-fang trough, South China

Yajun Xu, Peter A. Cawood, Yuansheng Du, Lisha Hu

Research output: Contribution to journalArticleResearchpeer-review

Abstract

The Qin-Fang Trough, South China, trends northeast-southwest, orthogonal to the adjoining southern margin of the craton. The Devonian strata within the trough are unconformable on late Neoproterozoic units of the Yunkai Massif, indicating that strata within the trough are autochthonous. U-Pb ages and Hf isotope compositions of detrital zircons from the Silurian to Devonian succession are consistent with derivation from the massif. In comparisons of our data with those frome quivalent units in the Ailaoshan Belt and Hainan Island, detrital zircons from the Silurian strata show similar age distributions and Hf isotope compositions, indicating that the three areas shared a common source and were adjacent to each other during the Silurian. In contrast, the age distributions of detrital zircons preserved in Devonian strata in the Qin-Fang area are different from those of equivalent units in the Ailaoshan Belt. This, along with the absence of Devonian strata on Hainan Island, suggests that the Qin-Fang area had separated from the Ailaoshan Belt by the Devonian. This change is linked to opening of the Ailaoshan Ocean, which was synchronous with expansion of the Qin-Fang Trough and the adjoining Youjiang Basin into epicontinental basins during the Devonian and Carboniferous. Combining these findings with temporal and spatial correlations, we conclude that the Qin-Fang Trough originated as an aulacogen: a “failed” rift of a three-armed rift system, with the other two rift arms evolving into the Ailaoshan Ocean during the opening of Paleo-Tethys. The Ailaoshan Ocean was an Atlantic-type oceanic basin with rifting commencing in the Early Silurian.

Original languageEnglish
Pages (from-to)531-550
Number of pages20
JournalJournal of Geology
Volume125
Issue number5
DOIs
Publication statusPublished - 2017

Cite this

@article{17aec039985d425da8d3f34fc0c32300,
title = "Aulacogen formation in response to opening the ailaoshan ocean: Origin of the qin-fang trough, South China",
abstract = "The Qin-Fang Trough, South China, trends northeast-southwest, orthogonal to the adjoining southern margin of the craton. The Devonian strata within the trough are unconformable on late Neoproterozoic units of the Yunkai Massif, indicating that strata within the trough are autochthonous. U-Pb ages and Hf isotope compositions of detrital zircons from the Silurian to Devonian succession are consistent with derivation from the massif. In comparisons of our data with those frome quivalent units in the Ailaoshan Belt and Hainan Island, detrital zircons from the Silurian strata show similar age distributions and Hf isotope compositions, indicating that the three areas shared a common source and were adjacent to each other during the Silurian. In contrast, the age distributions of detrital zircons preserved in Devonian strata in the Qin-Fang area are different from those of equivalent units in the Ailaoshan Belt. This, along with the absence of Devonian strata on Hainan Island, suggests that the Qin-Fang area had separated from the Ailaoshan Belt by the Devonian. This change is linked to opening of the Ailaoshan Ocean, which was synchronous with expansion of the Qin-Fang Trough and the adjoining Youjiang Basin into epicontinental basins during the Devonian and Carboniferous. Combining these findings with temporal and spatial correlations, we conclude that the Qin-Fang Trough originated as an aulacogen: a “failed” rift of a three-armed rift system, with the other two rift arms evolving into the Ailaoshan Ocean during the opening of Paleo-Tethys. The Ailaoshan Ocean was an Atlantic-type oceanic basin with rifting commencing in the Early Silurian.",
author = "Yajun Xu and Cawood, {Peter A.} and Yuansheng Du and Lisha Hu",
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language = "English",
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journal = "Journal of Geology",
issn = "0022-1376",
publisher = "The University of Chicago Press",
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Aulacogen formation in response to opening the ailaoshan ocean : Origin of the qin-fang trough, South China. / Xu, Yajun; Cawood, Peter A.; Du, Yuansheng; Hu, Lisha.

In: Journal of Geology, Vol. 125, No. 5, 2017, p. 531-550.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Aulacogen formation in response to opening the ailaoshan ocean

T2 - Origin of the qin-fang trough, South China

AU - Xu, Yajun

AU - Cawood, Peter A.

AU - Du, Yuansheng

AU - Hu, Lisha

PY - 2017

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N2 - The Qin-Fang Trough, South China, trends northeast-southwest, orthogonal to the adjoining southern margin of the craton. The Devonian strata within the trough are unconformable on late Neoproterozoic units of the Yunkai Massif, indicating that strata within the trough are autochthonous. U-Pb ages and Hf isotope compositions of detrital zircons from the Silurian to Devonian succession are consistent with derivation from the massif. In comparisons of our data with those frome quivalent units in the Ailaoshan Belt and Hainan Island, detrital zircons from the Silurian strata show similar age distributions and Hf isotope compositions, indicating that the three areas shared a common source and were adjacent to each other during the Silurian. In contrast, the age distributions of detrital zircons preserved in Devonian strata in the Qin-Fang area are different from those of equivalent units in the Ailaoshan Belt. This, along with the absence of Devonian strata on Hainan Island, suggests that the Qin-Fang area had separated from the Ailaoshan Belt by the Devonian. This change is linked to opening of the Ailaoshan Ocean, which was synchronous with expansion of the Qin-Fang Trough and the adjoining Youjiang Basin into epicontinental basins during the Devonian and Carboniferous. Combining these findings with temporal and spatial correlations, we conclude that the Qin-Fang Trough originated as an aulacogen: a “failed” rift of a three-armed rift system, with the other two rift arms evolving into the Ailaoshan Ocean during the opening of Paleo-Tethys. The Ailaoshan Ocean was an Atlantic-type oceanic basin with rifting commencing in the Early Silurian.

AB - The Qin-Fang Trough, South China, trends northeast-southwest, orthogonal to the adjoining southern margin of the craton. The Devonian strata within the trough are unconformable on late Neoproterozoic units of the Yunkai Massif, indicating that strata within the trough are autochthonous. U-Pb ages and Hf isotope compositions of detrital zircons from the Silurian to Devonian succession are consistent with derivation from the massif. In comparisons of our data with those frome quivalent units in the Ailaoshan Belt and Hainan Island, detrital zircons from the Silurian strata show similar age distributions and Hf isotope compositions, indicating that the three areas shared a common source and were adjacent to each other during the Silurian. In contrast, the age distributions of detrital zircons preserved in Devonian strata in the Qin-Fang area are different from those of equivalent units in the Ailaoshan Belt. This, along with the absence of Devonian strata on Hainan Island, suggests that the Qin-Fang area had separated from the Ailaoshan Belt by the Devonian. This change is linked to opening of the Ailaoshan Ocean, which was synchronous with expansion of the Qin-Fang Trough and the adjoining Youjiang Basin into epicontinental basins during the Devonian and Carboniferous. Combining these findings with temporal and spatial correlations, we conclude that the Qin-Fang Trough originated as an aulacogen: a “failed” rift of a three-armed rift system, with the other two rift arms evolving into the Ailaoshan Ocean during the opening of Paleo-Tethys. The Ailaoshan Ocean was an Atlantic-type oceanic basin with rifting commencing in the Early Silurian.

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U2 - 10.1086/693036

DO - 10.1086/693036

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VL - 125

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EP - 550

JO - Journal of Geology

JF - Journal of Geology

SN - 0022-1376

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