TY - JOUR
T1 - Permo-Triassic granitoids, Hainan Island, link to Paleotethyan not Paleopacific tectonics
AU - He, Huiying
AU - Wang, Yuejun
AU - Cawood, Peter A.
AU - Qian, Xin
AU - Zhang, Yuzhi
AU - Zhao, Guofeng
PY - 2020/9/1
Y1 - 2020/9/1
N2 - Hainan Island may have lain at the boundary between the Tethyan and Pacific domains since the late Paleozoic. Permo-Triassic granitoids outcropped on the island provide insight into Mesozoic tectonic evolution and potential dynamics. Based on analyses of zircon U-Pb geochronological and Hf-O isotopic data, along with whole-rock elemental and Sr-Nd isotopic data, the Permo-Triassic granitoids are divided into three groups: Late Permian (256-252 Ma) gneissic granitoids (Group 1), Early-Middle Triassic (247-244 Ma) massive granitoids (Group 2), and Middle-Late Triassic (242-225 Ma) massive granitoids (Group 3). Groups 1 and 2 exhibit similar elemental and Sr-Nd isotopic compositions with εNd(t) values ranging from -6.71 to -3.25. Group 1 is characterized by gneissic foliation and calc-alkaline I-type geochemical affinities with negative Nb-Ta and Ti anomalies; it has low εHf(t) (-4.2~+0.2) and high γ18O values (9.35-10.46‰), possibly related to derivation of a metabasite source in a continental arc setting. The Group 2 samples are peraluminous massive granitoids with slightly high A/CNK ratios of 1.00-1.31, d18O values (8.85-11.75‰), and high Sr/Y ratios but low εHf(t) (-8.7~+1.6) values. They may have originated from the mixed source of greywacke and metabasite, indicating a compressive tectonic setting. The Group 3 high-K calc-alkaline granitoids have high zircon temperatures (842-867 °C) and show the geochemical signatures of A-type granites. They are featured by slightly low whole- rock εNd(t) and zircon εHf(t) values, suggestive of the derivation from a metabasite-greywacke source in an extensional setting. In combination with other geochronological and geochemical data from Hainan Island, it is proposed that the Permian-Triassic igneous magmatism in Hainan Island reflects a continuous amalgamation process from back-arc consumption (272-252 Ma) to orogenic assembly (251-243 Ma) and orogenic collapse (242-225 Ma) between the South China and Indochina Blocks. Such a temporal- spatial pattern for the Hainan granitoids is consistent with that along the Truong Son, Jinshajiang-Ailaoshan-Song Ma tectonic zone, suggesting dominant control of Paleotethyan domain instead of Paleopacific tectonics.
AB - Hainan Island may have lain at the boundary between the Tethyan and Pacific domains since the late Paleozoic. Permo-Triassic granitoids outcropped on the island provide insight into Mesozoic tectonic evolution and potential dynamics. Based on analyses of zircon U-Pb geochronological and Hf-O isotopic data, along with whole-rock elemental and Sr-Nd isotopic data, the Permo-Triassic granitoids are divided into three groups: Late Permian (256-252 Ma) gneissic granitoids (Group 1), Early-Middle Triassic (247-244 Ma) massive granitoids (Group 2), and Middle-Late Triassic (242-225 Ma) massive granitoids (Group 3). Groups 1 and 2 exhibit similar elemental and Sr-Nd isotopic compositions with εNd(t) values ranging from -6.71 to -3.25. Group 1 is characterized by gneissic foliation and calc-alkaline I-type geochemical affinities with negative Nb-Ta and Ti anomalies; it has low εHf(t) (-4.2~+0.2) and high γ18O values (9.35-10.46‰), possibly related to derivation of a metabasite source in a continental arc setting. The Group 2 samples are peraluminous massive granitoids with slightly high A/CNK ratios of 1.00-1.31, d18O values (8.85-11.75‰), and high Sr/Y ratios but low εHf(t) (-8.7~+1.6) values. They may have originated from the mixed source of greywacke and metabasite, indicating a compressive tectonic setting. The Group 3 high-K calc-alkaline granitoids have high zircon temperatures (842-867 °C) and show the geochemical signatures of A-type granites. They are featured by slightly low whole- rock εNd(t) and zircon εHf(t) values, suggestive of the derivation from a metabasite-greywacke source in an extensional setting. In combination with other geochronological and geochemical data from Hainan Island, it is proposed that the Permian-Triassic igneous magmatism in Hainan Island reflects a continuous amalgamation process from back-arc consumption (272-252 Ma) to orogenic assembly (251-243 Ma) and orogenic collapse (242-225 Ma) between the South China and Indochina Blocks. Such a temporal- spatial pattern for the Hainan granitoids is consistent with that along the Truong Son, Jinshajiang-Ailaoshan-Song Ma tectonic zone, suggesting dominant control of Paleotethyan domain instead of Paleopacific tectonics.
UR - http://www.scopus.com/inward/record.url?scp=85089411648&partnerID=8YFLogxK
U2 - 10.1130/B35370.1
DO - 10.1130/B35370.1
M3 - Article
AN - SCOPUS:85089411648
VL - 132
SP - 2067
EP - 2083
JO - Geological Society of America Bulletin
JF - Geological Society of America Bulletin
SN - 0016-7606
IS - 9-10
ER -