TY - JOUR
T1 - Oxygen- and strontium-isotopic investigations of subduction zone volcanism
T2 - the case of the Volcano Arc and the Marianas Island Arc
AU - Ito, Emi
AU - Stern, Robert J.
PY - 1986/1
Y1 - 1986/1
N2 - Recent, fresh, volcanic rocks of the intra-oceanic Mariana and Volcano Arcs were analyzed for O and Sr isotopic compositions in order to determine the source of these magmas. Fresh, non-arc, volcanic rocks from the regions surrounding the Mariana-Volcano Arcs and some DSDP sediments were also analyzed for comparison. The oxygen isotopic ratios of the arc lavas (5.5-6.8‰) exhibited a small inter-island variation that cannot be entirely explained by fractional crystallization. The Sr isotopic composition of the arc lavas is remarkably uniform (0.70332-0.70394 for the Marianas). Three models are considered in order to explain the observed isotopic characteristics: (1) bulk mixing and melting of MORB-type mantle with (a) subducted sediments, and (b) subducted oceanic crust (excluding sediments); (2) melting of a mixture of sediment-derived fluids and MORB-type mantle; and (3) melting of a mixture of sediment-derived fluids and oceanic island or "hot-spot" type mantle. The last model fits the data best. The conclusion that very small, and variable, amounts of sediment-derived fluid (≤ 1%) are required to explain the observed inter-island O isotopic variation, is consistent with that of other workers who used different isotopic and trace element methods. The generation of magmas in the Mariana-Volcano Arcs involves very little sediment and the source region of Mariana lavas is isotopically indistinguishable from that of hot-spot basalts.
AB - Recent, fresh, volcanic rocks of the intra-oceanic Mariana and Volcano Arcs were analyzed for O and Sr isotopic compositions in order to determine the source of these magmas. Fresh, non-arc, volcanic rocks from the regions surrounding the Mariana-Volcano Arcs and some DSDP sediments were also analyzed for comparison. The oxygen isotopic ratios of the arc lavas (5.5-6.8‰) exhibited a small inter-island variation that cannot be entirely explained by fractional crystallization. The Sr isotopic composition of the arc lavas is remarkably uniform (0.70332-0.70394 for the Marianas). Three models are considered in order to explain the observed isotopic characteristics: (1) bulk mixing and melting of MORB-type mantle with (a) subducted sediments, and (b) subducted oceanic crust (excluding sediments); (2) melting of a mixture of sediment-derived fluids and MORB-type mantle; and (3) melting of a mixture of sediment-derived fluids and oceanic island or "hot-spot" type mantle. The last model fits the data best. The conclusion that very small, and variable, amounts of sediment-derived fluid (≤ 1%) are required to explain the observed inter-island O isotopic variation, is consistent with that of other workers who used different isotopic and trace element methods. The generation of magmas in the Mariana-Volcano Arcs involves very little sediment and the source region of Mariana lavas is isotopically indistinguishable from that of hot-spot basalts.
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U2 - 10.1016/0012-821X(86)90082-8
DO - 10.1016/0012-821X(86)90082-8
M3 - Article
AN - SCOPUS:0022554992
VL - 76
SP - 312
EP - 320
JO - Earth and Planetary Sciences Letters
JF - Earth and Planetary Sciences Letters
SN - 0012-821X
IS - 3-4
ER -