Subduction polarity reversal typically occurs in intra-oceanic arc settings;the existence of an ancient intraoceanic arc and its associated back-arc system within the Neotethyan plate has been deliberated.In this stud...Subduction polarity reversal typically occurs in intra-oceanic arc settings;the existence of an ancient intraoceanic arc and its associated back-arc system within the Neotethyan plate has been deliberated.In this study,we investigate the possible role of subduction initiation of polarity reversal in the formation of Nagaland-Manipur ophiolite(NMO),evaluate the petrological and geochronological data and compare it with the neighboring natural examples of subduction polarity reversal of the Andaman-Nicobar ophiolite(ANO).The ancient intra-oceanic arc,namely the Incertus-Woyla Arc,and its associated back-arc remnant have been correlated with the back-arc mafic of the ANO.We found that the geochemical signatures of mafic rocks of NMO and ANO are comparable,and the available geochronology data of~145 Ma from the NMO basalt and chert fit well with the evolution and formation of the intra-oceanic arc,i.e.,Incertus-Woyla Arc.The evolution and age of the Incertus-Woyla Arc are between 135 and 150 Ma.Although the oldest age of the ANO has been reported from metamor-phic sole at about 106.4 and 105.3 Ma,the back-arc affinity of the amphibole has been credited to the back-arc spreading that occurred behind the Woyla Arc.Previous paleomagnetic and geochronological studies have suggested that the development of the back-arc basin behind the Incertus-Woyla Arc was a result of divergent double subduction.Therefore,we have inferred a similar scenario for the development of the back-arc affinity rocks of the NMO behind the Incertus-Woyla Arc and the reinterpretation for the evolution of the supra-subduction zone affinity rocks of NMO and ANO during subduction initiation after subduction polarity reversal.展开更多
基金supported by the Ministry of Earth Sciences(MoES),Government of India,New Delhi,through a research grant(No.MoES/P.O.(Geo)/80/2015)to A.K.Singh.
文摘Subduction polarity reversal typically occurs in intra-oceanic arc settings;the existence of an ancient intraoceanic arc and its associated back-arc system within the Neotethyan plate has been deliberated.In this study,we investigate the possible role of subduction initiation of polarity reversal in the formation of Nagaland-Manipur ophiolite(NMO),evaluate the petrological and geochronological data and compare it with the neighboring natural examples of subduction polarity reversal of the Andaman-Nicobar ophiolite(ANO).The ancient intra-oceanic arc,namely the Incertus-Woyla Arc,and its associated back-arc remnant have been correlated with the back-arc mafic of the ANO.We found that the geochemical signatures of mafic rocks of NMO and ANO are comparable,and the available geochronology data of~145 Ma from the NMO basalt and chert fit well with the evolution and formation of the intra-oceanic arc,i.e.,Incertus-Woyla Arc.The evolution and age of the Incertus-Woyla Arc are between 135 and 150 Ma.Although the oldest age of the ANO has been reported from metamor-phic sole at about 106.4 and 105.3 Ma,the back-arc affinity of the amphibole has been credited to the back-arc spreading that occurred behind the Woyla Arc.Previous paleomagnetic and geochronological studies have suggested that the development of the back-arc basin behind the Incertus-Woyla Arc was a result of divergent double subduction.Therefore,we have inferred a similar scenario for the development of the back-arc affinity rocks of the NMO behind the Incertus-Woyla Arc and the reinterpretation for the evolution of the supra-subduction zone affinity rocks of NMO and ANO during subduction initiation after subduction polarity reversal.
