Implications of Eocene age Philippine Sea and fore-arc basalts for initiation and early history of the Izu-Bonin-Mariana Arc

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doi: 10.1016/j.gca.2018.02.047
Author(s): Yogodzinski, Gene M.; Bizimis, Michael; Hickey-Vargas, Rosemary; McCarthy, Anders; Hocking, Benjamin D.; Savov, Ivan P.; Ishizuka, Osamu; Arculus, Richard J.
Author Affiliation(s): Primary:
University of South Carolina, School of Earth, Ocean, and Environment, Columbia, SC, United States
Florida International University, United States
University of Lausanne, Switzerland
University of Leeds, United Kingdom
Japanese Geological Survey, Japan
Australian National University, Australia
Volume Title: Geochimica et Cosmochimica Acta
Source: Geochimica et Cosmochimica Acta, Vol.228, p.136-156. Publisher: Elsevier, New York, NY, International. ISSN: 0016-7037 CODEN: GCACAK
Note: In English. Includes appendices. 88 refs.; illus., incl. 5 tables, sketch map
Summary: Whole-rock isotope ratio (Hf, Nd, Pb, Sr) and trace element data for basement rocks at ocean drilling Sites U1438, 1201 and 447 immediately west of the KPR (Kyushu-Palau Ridge) are compared to those of FAB (forearc basalts) previously interpreted to be the initial products of IBM subduction volcanism. West-of-KPR basement basalts (drill sites U1438, 1201, 447) and FAB occupy the same Hf-Nd and Pb-Pb isotopic space and share distinctive source characteristics with εHf mostly > 16.5 and up to εHf = 19.8, which is more radiogenic than most Indian mid-ocean ridge basalts (MORB). Lead isotopic ratios are depleted, with 206Pb/204Pb = 17.8-18.8 accompanying relatively high 208Pb/204Pb, indicating an Indian-MORB source unlike that of West Philippine Basin plume basalts. Some Sr isotopes show affects of seawater alteration, but samples with 87Sr/86Sr < 0.7034 and εNd > 8.0 appear to preserve magmatic compositions and also indicate a common source for west-of-KPR basement and FAB. Trace element ratios resistant to seawater alteration (La/Yb, Lu/Hf, Zr/Nb, Sm/Nd) in west-of-KPR basement are generally more depleted than normal MORB and so also appear similar to FAB. At Site U1438, only andesite sills intruding sedimentary rocks overlying the basement have subduction-influenced geochemical characteristics (εNd ∼ 6.6, εHf ∼ 13.8, La/Yb > 2.5, Nd/Hf ∼ 9). The key characteristic that unites drill site basement rocks west of KPR and FAB is the nature of their source, which is more depleted in lithophile trace elements than average MORB but with Hf, Nd, and Pb isotope ratios that are common in MORB. The lithophile element-depleted nature of FAB has been linked to initiation of IBM subduction in the Eocene, but Sm-Nd model ages and errorchron relationships in Site U1438 basement indicate that the depleted character of the rocks is a regional characteristic that was produced well prior to the time of subduction initiation and persists today in the source of modern IBM arc volcanic rocks with Sm/Nd > 0.34 and εNd ∼ 9.0.
Year of Publication: 2018
Research Program: DSDP Deep Sea Drilling Project
IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 02 Geochemistry; 05 Petrology, Igneous and Metamorphic; Alkaline earth metals; Basalts; Basement; Basins; Cenozoic; Crust; DSDP Site 447; Deep Sea Drilling Project; Eocene; Expedition 351; Fore-arc basins; Hafnium; IODP Site U1438; IPOD; Igneous rocks; International Ocean Discovery Program; Island arcs; Isotope ratios; Isotopes; Izu-Bonin Arc; Kyushu-Palau Ridge; Lead; Leg 195; Leg 59; Major elements; Mariana Islands; Metals; Micronesia; Mid-ocean ridge basalts; North Pacific; Northwest Pacific; ODP Site 1201; Ocean Drilling Program; Oceania; Oceanic crust; Pacific Ocean; Paleogene; Philippine Sea; Philippine Sea Plate; Plate tectonics; Rare earths; Sr-87/Sr-86; Stable isotopes; Strontium; Tertiary; Trace elements; Volcanic rocks; West Pacific; West Philippine Basin
Coordinates: N272300 N272301 E1341907 E1341905
Record ID: 2018059324
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands