Hafnium isotope evidence for slab melt contributions in the Central Mexican volcanic belt and implications for slab melting in hot and cold slab arcs

Online Access: Get full text
doi: 10.1016/j.chemgeo.2014.04.002
Author(s): Cai, Yue; LaGatta, Alexandra; Goldstein, Steven L.; Langmuir, Charles H.; Gómez Tuena, Arturo; Martín del Pozzo, Ana Lillian; Carrasco Núñez, Gerardo
Author Affiliation(s): Primary:
Lamont-Doherty Earth Observatory, Palisades, NY, United States
Other:
Harvard University, United States
Universidad Nacional Autónoma de México, Mexico
Volume Title: Chemical Geology
Source: Chemical Geology, Vol.377, p.45-55. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0009-2541 CODEN: CHGEAD
Note: In English. Includes appendices. 120 refs.; illus., incl. sketch map
Summary: This study presents evidence that Quaternary frontal arc calc-alkaline lavas from Central Mexican Volcanic Belt (CMVB) contain contributions from partial melts of the subducting garnet-bearing eclogitic oceanic crust and sediment, based on chemical and Hf-Nd isotope data. The CMVB includes both calc-alkaline lavas with arc-type trace element patterns such as aqueous fluid mobile element enrichments and high field strength element depletions; and "high-Nb" alkaline lavas with trace element patterns similar to ocean island basalts. The two types of lavas are closely related geographically and temporally. Distinct from the high-Nb lavas, the calc-alkaline lavas show trends toward higher 176Hf/177Hf and 143Nd/144Nd ratios coupled with lower Lu/Hf. The high Hf-Nd isotope ratios fingerprint contributions of subducted basaltic ocean crust, while the correlation with low Lu/Hf indicates melting in the presence of residual garnet, which reflects conversion of the subducted oceanic crust to eclogite. Isotopic and chemical mass balance considerations indicate that the slab melts are ∼80% basaltic oceanic crust and ∼20% subducted sediment. The calc-alkaline lavas have higher SiO2 at a given Mg# compared to the high-Nb alkaline lavas, also reflecting melt contributions from the subducted slab. A survey of global arc lavas shows that calc-alkaline lavas with low Lu/Hf ratios, reflecting melting in the presence of residual garnet and preferential mobilization of Hf over Lu from the subducted slab, are generally associated with hot slab conditions. These include arcs where young (<30 Ma old) ocean crust is subducted (e.g. Mexican Volcanic Belt, Cascades, Austral Andes, Luzon, Setouchi), where slab tearing occurred and hot asthenospheric mantle could upwell through the slab window (e.g., western Aleutians, Sunda, southern Scotia), and where oblique or slow subduction leads to higher slab temperatures (e.g. Lesser Antilles, western Aleutians). In some of these hot slab arcs, where low Lu/Hf ratios are coupled with high Nd-Hf isotope ratios, slab melt contributions are dominated by partial melts from the subducted oceanic basalt (e.g., Mexican Volcanic Belt, Aleutians and Cascades). In other hot slab arcs, low Lu/Hf ratios are coupled with low Nd-Hf isotope ratios, reflecting slab contributions dominated by sediment melts (e.g. Setouchi, Lesser Antilles, Luzon, Sunda, and southern Scotia). Arcs associated with colder subducted oceanic crust (e.g. Izu-Bonin-Marianas, Tonga-Kermadec, central and northern Scotia) erupt lavas with high Lu/Hf along with high Hf-Nd isotope ratios, similar to mid-ocean ridge basalts, thus they lack the signature of residual garnet as well as significant slab melt input. Abstract Copyright (2014) Elsevier, B.V.
Year of Publication: 2014
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; 05 Petrology, Igneous and Metamorphic; Chemical composition; Crust; DSDP Site 487; Deep Sea Drilling Project; East Pacific; Hafnium; Hf-177/Hf-176; ICP mass spectra; IPOD; Igneous rocks; Island arcs; Isotope ratios; Isotopes; Leg 66; Lu/Hf; Magmas; Marine sediments; Mass spectra; Melting; Melts; Metals; Mexico; Middle America Trench; Nd-144/Nd-143; Neodymium; North Pacific; Northeast Pacific; Oceanic crust; Pacific Ocean; Pacific Plate; Partitioning; Plate tectonics; Rare earths; Sediments; Silicate melts; Slabs; Spectra; Stable isotopes; Subduction zones; Trans-Mexican volcanic belt; Volcanic belts; Volcanic rocks; X-ray fluorescence spectra
Coordinates: N183000 N193000 W0970000 W1000000
N155113 N155113 W0991031 W0991031
Record ID: 2014064504
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands