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Yaoling Niu - One of the best experts on this subject based on the ideXlab platform.
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Tholeiite boninite terrane in the north qilian suture zone implications for subduction initiation and back arc basin development
Chemical Geology, 2012Co-Authors: Xiaohong Xia, Shuguang Song, Yaoling NiuAbstract:Abstract A Tholeiite–boninite terrane occurs as a ~ 4.5-km-thick massif with lavas and intrusions in the Dachadaban (DCDB) area, the middle part of the North Qilian oceanic-type suture zone. It comprises two distinct lithological groups: the lower Tholeiite unit and the upper boninite unit. The lower Tholeiite unit consists of massive lava flows and subordinate gabbro intrusions with MORB-like characteristics that could represent 5–6% melting of an enriched MORB mantle. In contrast, the overlying boninite unit consists of pillow lavas, dolerite dykes and gabbro intrusions and shows high-Ca boninite features that may be formed by continuous melting of the extremely refractory mantle with the aid of a combination of the elevated mantle potential temperature of 1380–1460 °C at depths of 42–66 km and involvement of slab-derived hydrous fluids/melts. Zircon U–Pb SHRIMP dating shows that lower Tholeiite magmatism lasted for at least 12 M.y. from 517 Ma to 505 Ma and upper boninite volcanism occurred between 505 and 487 Ma, which is consistent with the earliest age (486 ± 7 Ma) of the SSZ-type ophiolite belt immediately north of the Dachaidaban (DCDB) Tholeiite–boninite terrane. The lower Tholeiites are considered to represent the products of earliest infant arc magmatism by decompression-induced partial melting of the relatively “dry” and fertile upwelling mantle in response to the onset of subduction. The upper boninite unit with younger age of 487 ± 9 Ma is interpreted as earliest products of infant arc splitting and subsequent back-arc basin development. Therefore, the long-lived DCDB Tholeiite–boninite sequence presents a key lithological record of early stages of supra-subduction zone magmatic activity evolved from subduction initiation at ~ 517 Ma to back-arc extension at ~ 487 Ma.
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Tholeiite–Boninite terrane in the North Qilian suture zone: Implications for subduction initiation and back-arc basin development
Chemical Geology, 2012Co-Authors: Xiaohong Xia, Shuguang Song, Yaoling NiuAbstract:Abstract A Tholeiite–boninite terrane occurs as a ~ 4.5-km-thick massif with lavas and intrusions in the Dachadaban (DCDB) area, the middle part of the North Qilian oceanic-type suture zone. It comprises two distinct lithological groups: the lower Tholeiite unit and the upper boninite unit. The lower Tholeiite unit consists of massive lava flows and subordinate gabbro intrusions with MORB-like characteristics that could represent 5–6% melting of an enriched MORB mantle. In contrast, the overlying boninite unit consists of pillow lavas, dolerite dykes and gabbro intrusions and shows high-Ca boninite features that may be formed by continuous melting of the extremely refractory mantle with the aid of a combination of the elevated mantle potential temperature of 1380–1460 °C at depths of 42–66 km and involvement of slab-derived hydrous fluids/melts. Zircon U–Pb SHRIMP dating shows that lower Tholeiite magmatism lasted for at least 12 M.y. from 517 Ma to 505 Ma and upper boninite volcanism occurred between 505 and 487 Ma, which is consistent with the earliest age (486 ± 7 Ma) of the SSZ-type ophiolite belt immediately north of the Dachaidaban (DCDB) Tholeiite–boninite terrane. The lower Tholeiites are considered to represent the products of earliest infant arc magmatism by decompression-induced partial melting of the relatively “dry” and fertile upwelling mantle in response to the onset of subduction. The upper boninite unit with younger age of 487 ± 9 Ma is interpreted as earliest products of infant arc splitting and subsequent back-arc basin development. Therefore, the long-lived DCDB Tholeiite–boninite sequence presents a key lithological record of early stages of supra-subduction zone magmatic activity evolved from subduction initiation at ~ 517 Ma to back-arc extension at ~ 487 Ma.
Timothy L. Grove - One of the best experts on this subject based on the ideXlab platform.
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melt harzburgite reaction in the petrogenesis of tholeiitic magma from kilauea volcano hawaii
Contributions to Mineralogy and Petrology, 1998Co-Authors: T P Wagner, Timothy L. GroveAbstract:We use the results of elevated pressure melting experiments to constrain the role of melt/mantle reaction in the formation of tholeiitic magma from Kilauea volcano, Hawaii. Trace element abundance data is commonly interpreted as evidence that Kilauea Tholeiite is produced by partial melting of garnet lherzolite. We experimentally determine the liquidus relations of a tightly constrained estimate of primary Tholeiite composition, and find that it is not in equilibrium on its liquidus with a garnet lherzolite assemblage at any pressure. The composition is, however, cosaturated on its liquidus with olivine and orthopyroxene at 1.4 GPa and 1425 °C, from which we infer that primary Tholeiite is in equilibrium with harzburgite at lithospheric depths beneath Kilauea. These results are consistent with our observation that Tholeiite primary magmas have higher normative silica contents than experimentally produced melts of garnet lherzolite. A model is presented whereby primary Tholeiite forms via a two-stage process. In the first stage, magmas are generated by melting of garnet lherzolite in a mantle plume. In the second stage, the ascent and decompression of magmas causes them to react with harzburgite in the mantle by assimilating orthopyroxene and crystallizing olivine. This reaction can produce typical Tholeiite primary magmas from significantly less siliceous garnet lherzolite melts, and is consistent with the shift in liquidus boundaries that accompanies decompression of an ascending magma. We determine the proportion of reactants by major element mass balance. The ratio of mass assimilated to mass crystallized (Ma/Mc) varies from 2.7 to 1.4, depending on the primary magma composition. We use an AFC calculation to model the effect of melt/harzburgite reaction on melt rare earth and high field strength element abundances, and find that reaction dilutes, but does not significantly fractionate, the abundances of these elements. Assuming olivine and orthopyroxene have similar heats of fusion, the Ma/Mc ratio indicates that reaction is endothermic. The additional thermal energy is supplied by the melt, which becomes superheated during adiabatic ascent and can provide more thermal energy than required. Melt/harzburgite reaction likely occurs over a range of depths, and we infer a mean depth of 42 km from our experimental results. This depth is well within the lithosphere beneath Kilauea. Since geochemical evidence indicates that melt/harzburgite reaction likely occurs in the top of the Hawaiian plume, the plume must be able to thin a significant portion of the lithosphere.
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Melt/harzburgite reaction in the petrogenesis of tholeiitic magma from Kilauea volcano, Hawaii
Contributions to Mineralogy and Petrology, 1998Co-Authors: T P Wagner, Timothy L. GroveAbstract:We use the results of elevated pressure melting experiments to constrain the role of melt/mantle reaction in the formation of tholeiitic magma from Kilauea volcano, Hawaii. Trace element abundance data is commonly interpreted as evidence that Kilauea Tholeiite is produced by partial melting of garnet lherzolite. We experimentally determine the liquidus relations of a tightly constrained estimate of primary Tholeiite composition, and find that it is not in equilibrium on its liquidus with a garnet lherzolite assemblage at any pressure. The composition is, however, cosaturated on its liquidus with olivine and orthopyroxene at 1.4 GPa and 1425 °C, from which we infer that primary Tholeiite is in equilibrium with harzburgite at lithospheric depths beneath Kilauea. These results are consistent with our observation that Tholeiite primary magmas have higher normative silica contents than experimentally produced melts of garnet lherzolite. A model is presented whereby primary Tholeiite forms via a two-stage process. In the first stage, magmas are generated by melting of garnet lherzolite in a mantle plume. In the second stage, the ascent and decompression of magmas causes them to react with harzburgite in the mantle by assimilating orthopyroxene and crystallizing olivine. This reaction can produce typical Tholeiite primary magmas from significantly less siliceous garnet lherzolite melts, and is consistent with the shift in liquidus boundaries that accompanies decompression of an ascending magma. We determine the proportion of reactants by major element mass balance. The ratio of mass assimilated to mass crystallized (Ma/Mc) varies from 2.7 to 1.4, depending on the primary magma composition. We use an AFC calculation to model the effect of melt/harzburgite reaction on melt rare earth and high field strength element abundances, and find that reaction dilutes, but does not significantly fractionate, the abundances of these elements. Assuming olivine and orthopyroxene have similar heats of fusion, the Ma/Mc ratio indicates that reaction is endothermic. The additional thermal energy is supplied by the melt, which becomes superheated during adiabatic ascent and can provide more thermal energy than required. Melt/harzburgite reaction likely occurs over a range of depths, and we infer a mean depth of 42 km from our experimental results. This depth is well within the lithosphere beneath Kilauea. Since geochemical evidence indicates that melt/harzburgite reaction likely occurs in the top of the Hawaiian plume, the plume must be able to thin a significant portion of the lithosphere.
Xiaohong Xia - One of the best experts on this subject based on the ideXlab platform.
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Tholeiite boninite terrane in the north qilian suture zone implications for subduction initiation and back arc basin development
Chemical Geology, 2012Co-Authors: Xiaohong Xia, Shuguang Song, Yaoling NiuAbstract:Abstract A Tholeiite–boninite terrane occurs as a ~ 4.5-km-thick massif with lavas and intrusions in the Dachadaban (DCDB) area, the middle part of the North Qilian oceanic-type suture zone. It comprises two distinct lithological groups: the lower Tholeiite unit and the upper boninite unit. The lower Tholeiite unit consists of massive lava flows and subordinate gabbro intrusions with MORB-like characteristics that could represent 5–6% melting of an enriched MORB mantle. In contrast, the overlying boninite unit consists of pillow lavas, dolerite dykes and gabbro intrusions and shows high-Ca boninite features that may be formed by continuous melting of the extremely refractory mantle with the aid of a combination of the elevated mantle potential temperature of 1380–1460 °C at depths of 42–66 km and involvement of slab-derived hydrous fluids/melts. Zircon U–Pb SHRIMP dating shows that lower Tholeiite magmatism lasted for at least 12 M.y. from 517 Ma to 505 Ma and upper boninite volcanism occurred between 505 and 487 Ma, which is consistent with the earliest age (486 ± 7 Ma) of the SSZ-type ophiolite belt immediately north of the Dachaidaban (DCDB) Tholeiite–boninite terrane. The lower Tholeiites are considered to represent the products of earliest infant arc magmatism by decompression-induced partial melting of the relatively “dry” and fertile upwelling mantle in response to the onset of subduction. The upper boninite unit with younger age of 487 ± 9 Ma is interpreted as earliest products of infant arc splitting and subsequent back-arc basin development. Therefore, the long-lived DCDB Tholeiite–boninite sequence presents a key lithological record of early stages of supra-subduction zone magmatic activity evolved from subduction initiation at ~ 517 Ma to back-arc extension at ~ 487 Ma.
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Tholeiite–Boninite terrane in the North Qilian suture zone: Implications for subduction initiation and back-arc basin development
Chemical Geology, 2012Co-Authors: Xiaohong Xia, Shuguang Song, Yaoling NiuAbstract:Abstract A Tholeiite–boninite terrane occurs as a ~ 4.5-km-thick massif with lavas and intrusions in the Dachadaban (DCDB) area, the middle part of the North Qilian oceanic-type suture zone. It comprises two distinct lithological groups: the lower Tholeiite unit and the upper boninite unit. The lower Tholeiite unit consists of massive lava flows and subordinate gabbro intrusions with MORB-like characteristics that could represent 5–6% melting of an enriched MORB mantle. In contrast, the overlying boninite unit consists of pillow lavas, dolerite dykes and gabbro intrusions and shows high-Ca boninite features that may be formed by continuous melting of the extremely refractory mantle with the aid of a combination of the elevated mantle potential temperature of 1380–1460 °C at depths of 42–66 km and involvement of slab-derived hydrous fluids/melts. Zircon U–Pb SHRIMP dating shows that lower Tholeiite magmatism lasted for at least 12 M.y. from 517 Ma to 505 Ma and upper boninite volcanism occurred between 505 and 487 Ma, which is consistent with the earliest age (486 ± 7 Ma) of the SSZ-type ophiolite belt immediately north of the Dachaidaban (DCDB) Tholeiite–boninite terrane. The lower Tholeiites are considered to represent the products of earliest infant arc magmatism by decompression-induced partial melting of the relatively “dry” and fertile upwelling mantle in response to the onset of subduction. The upper boninite unit with younger age of 487 ± 9 Ma is interpreted as earliest products of infant arc splitting and subsequent back-arc basin development. Therefore, the long-lived DCDB Tholeiite–boninite sequence presents a key lithological record of early stages of supra-subduction zone magmatic activity evolved from subduction initiation at ~ 517 Ma to back-arc extension at ~ 487 Ma.
Shuguang Song - One of the best experts on this subject based on the ideXlab platform.
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Tholeiite boninite terrane in the north qilian suture zone implications for subduction initiation and back arc basin development
Chemical Geology, 2012Co-Authors: Xiaohong Xia, Shuguang Song, Yaoling NiuAbstract:Abstract A Tholeiite–boninite terrane occurs as a ~ 4.5-km-thick massif with lavas and intrusions in the Dachadaban (DCDB) area, the middle part of the North Qilian oceanic-type suture zone. It comprises two distinct lithological groups: the lower Tholeiite unit and the upper boninite unit. The lower Tholeiite unit consists of massive lava flows and subordinate gabbro intrusions with MORB-like characteristics that could represent 5–6% melting of an enriched MORB mantle. In contrast, the overlying boninite unit consists of pillow lavas, dolerite dykes and gabbro intrusions and shows high-Ca boninite features that may be formed by continuous melting of the extremely refractory mantle with the aid of a combination of the elevated mantle potential temperature of 1380–1460 °C at depths of 42–66 km and involvement of slab-derived hydrous fluids/melts. Zircon U–Pb SHRIMP dating shows that lower Tholeiite magmatism lasted for at least 12 M.y. from 517 Ma to 505 Ma and upper boninite volcanism occurred between 505 and 487 Ma, which is consistent with the earliest age (486 ± 7 Ma) of the SSZ-type ophiolite belt immediately north of the Dachaidaban (DCDB) Tholeiite–boninite terrane. The lower Tholeiites are considered to represent the products of earliest infant arc magmatism by decompression-induced partial melting of the relatively “dry” and fertile upwelling mantle in response to the onset of subduction. The upper boninite unit with younger age of 487 ± 9 Ma is interpreted as earliest products of infant arc splitting and subsequent back-arc basin development. Therefore, the long-lived DCDB Tholeiite–boninite sequence presents a key lithological record of early stages of supra-subduction zone magmatic activity evolved from subduction initiation at ~ 517 Ma to back-arc extension at ~ 487 Ma.
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Tholeiite–Boninite terrane in the North Qilian suture zone: Implications for subduction initiation and back-arc basin development
Chemical Geology, 2012Co-Authors: Xiaohong Xia, Shuguang Song, Yaoling NiuAbstract:Abstract A Tholeiite–boninite terrane occurs as a ~ 4.5-km-thick massif with lavas and intrusions in the Dachadaban (DCDB) area, the middle part of the North Qilian oceanic-type suture zone. It comprises two distinct lithological groups: the lower Tholeiite unit and the upper boninite unit. The lower Tholeiite unit consists of massive lava flows and subordinate gabbro intrusions with MORB-like characteristics that could represent 5–6% melting of an enriched MORB mantle. In contrast, the overlying boninite unit consists of pillow lavas, dolerite dykes and gabbro intrusions and shows high-Ca boninite features that may be formed by continuous melting of the extremely refractory mantle with the aid of a combination of the elevated mantle potential temperature of 1380–1460 °C at depths of 42–66 km and involvement of slab-derived hydrous fluids/melts. Zircon U–Pb SHRIMP dating shows that lower Tholeiite magmatism lasted for at least 12 M.y. from 517 Ma to 505 Ma and upper boninite volcanism occurred between 505 and 487 Ma, which is consistent with the earliest age (486 ± 7 Ma) of the SSZ-type ophiolite belt immediately north of the Dachaidaban (DCDB) Tholeiite–boninite terrane. The lower Tholeiites are considered to represent the products of earliest infant arc magmatism by decompression-induced partial melting of the relatively “dry” and fertile upwelling mantle in response to the onset of subduction. The upper boninite unit with younger age of 487 ± 9 Ma is interpreted as earliest products of infant arc splitting and subsequent back-arc basin development. Therefore, the long-lived DCDB Tholeiite–boninite sequence presents a key lithological record of early stages of supra-subduction zone magmatic activity evolved from subduction initiation at ~ 517 Ma to back-arc extension at ~ 487 Ma.
T P Wagner - One of the best experts on this subject based on the ideXlab platform.
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melt harzburgite reaction in the petrogenesis of tholeiitic magma from kilauea volcano hawaii
Contributions to Mineralogy and Petrology, 1998Co-Authors: T P Wagner, Timothy L. GroveAbstract:We use the results of elevated pressure melting experiments to constrain the role of melt/mantle reaction in the formation of tholeiitic magma from Kilauea volcano, Hawaii. Trace element abundance data is commonly interpreted as evidence that Kilauea Tholeiite is produced by partial melting of garnet lherzolite. We experimentally determine the liquidus relations of a tightly constrained estimate of primary Tholeiite composition, and find that it is not in equilibrium on its liquidus with a garnet lherzolite assemblage at any pressure. The composition is, however, cosaturated on its liquidus with olivine and orthopyroxene at 1.4 GPa and 1425 °C, from which we infer that primary Tholeiite is in equilibrium with harzburgite at lithospheric depths beneath Kilauea. These results are consistent with our observation that Tholeiite primary magmas have higher normative silica contents than experimentally produced melts of garnet lherzolite. A model is presented whereby primary Tholeiite forms via a two-stage process. In the first stage, magmas are generated by melting of garnet lherzolite in a mantle plume. In the second stage, the ascent and decompression of magmas causes them to react with harzburgite in the mantle by assimilating orthopyroxene and crystallizing olivine. This reaction can produce typical Tholeiite primary magmas from significantly less siliceous garnet lherzolite melts, and is consistent with the shift in liquidus boundaries that accompanies decompression of an ascending magma. We determine the proportion of reactants by major element mass balance. The ratio of mass assimilated to mass crystallized (Ma/Mc) varies from 2.7 to 1.4, depending on the primary magma composition. We use an AFC calculation to model the effect of melt/harzburgite reaction on melt rare earth and high field strength element abundances, and find that reaction dilutes, but does not significantly fractionate, the abundances of these elements. Assuming olivine and orthopyroxene have similar heats of fusion, the Ma/Mc ratio indicates that reaction is endothermic. The additional thermal energy is supplied by the melt, which becomes superheated during adiabatic ascent and can provide more thermal energy than required. Melt/harzburgite reaction likely occurs over a range of depths, and we infer a mean depth of 42 km from our experimental results. This depth is well within the lithosphere beneath Kilauea. Since geochemical evidence indicates that melt/harzburgite reaction likely occurs in the top of the Hawaiian plume, the plume must be able to thin a significant portion of the lithosphere.
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Melt/harzburgite reaction in the petrogenesis of tholeiitic magma from Kilauea volcano, Hawaii
Contributions to Mineralogy and Petrology, 1998Co-Authors: T P Wagner, Timothy L. GroveAbstract:We use the results of elevated pressure melting experiments to constrain the role of melt/mantle reaction in the formation of tholeiitic magma from Kilauea volcano, Hawaii. Trace element abundance data is commonly interpreted as evidence that Kilauea Tholeiite is produced by partial melting of garnet lherzolite. We experimentally determine the liquidus relations of a tightly constrained estimate of primary Tholeiite composition, and find that it is not in equilibrium on its liquidus with a garnet lherzolite assemblage at any pressure. The composition is, however, cosaturated on its liquidus with olivine and orthopyroxene at 1.4 GPa and 1425 °C, from which we infer that primary Tholeiite is in equilibrium with harzburgite at lithospheric depths beneath Kilauea. These results are consistent with our observation that Tholeiite primary magmas have higher normative silica contents than experimentally produced melts of garnet lherzolite. A model is presented whereby primary Tholeiite forms via a two-stage process. In the first stage, magmas are generated by melting of garnet lherzolite in a mantle plume. In the second stage, the ascent and decompression of magmas causes them to react with harzburgite in the mantle by assimilating orthopyroxene and crystallizing olivine. This reaction can produce typical Tholeiite primary magmas from significantly less siliceous garnet lherzolite melts, and is consistent with the shift in liquidus boundaries that accompanies decompression of an ascending magma. We determine the proportion of reactants by major element mass balance. The ratio of mass assimilated to mass crystallized (Ma/Mc) varies from 2.7 to 1.4, depending on the primary magma composition. We use an AFC calculation to model the effect of melt/harzburgite reaction on melt rare earth and high field strength element abundances, and find that reaction dilutes, but does not significantly fractionate, the abundances of these elements. Assuming olivine and orthopyroxene have similar heats of fusion, the Ma/Mc ratio indicates that reaction is endothermic. The additional thermal energy is supplied by the melt, which becomes superheated during adiabatic ascent and can provide more thermal energy than required. Melt/harzburgite reaction likely occurs over a range of depths, and we infer a mean depth of 42 km from our experimental results. This depth is well within the lithosphere beneath Kilauea. Since geochemical evidence indicates that melt/harzburgite reaction likely occurs in the top of the Hawaiian plume, the plume must be able to thin a significant portion of the lithosphere.
