Crustal contamination versus subduction zone enrichment: example from the lesser antilles and implications for mantle source compositions of island arc volcanic rocks

Journal Article · Sat Aug 01 04:00:00 EDT 1987 · Geochim. Cosmochim. Acta; (United States)

DOI:https://doi.org/10.1016/0016-7037(87)90268-7· OSTI ID:5064489

Davidson, J P

Isotopic and geochemical data are presented from the northern and central Lesser Antilles arc. Island arc tholeiites from the northern islands are restricted in /sup 143/Nd//sup 144/Nd and /sup 87/Sr//sup 86/Sr and show large enrichments in LILE relative to other trace elements, as exemplified particularly in high Ba/La ratios. In contrast, samples from the central islands (Martinique and St. Lucia) are highly variable in isotopic and trace element ratios, and reflect overprinting of primitive island arc magma chemistry by subsequent crustal contamination. Such magmas therefore do no represent island arc mantle source characteristics. Northern Lesser Antilles arc mantle sources are displaced from MORB Pb isotopic compositions towards the higher /sup 207/Pb//sup 204/Pb ratios characteristic of sediments. Also, Sr and Nd isotopic compositions are highly restricted and distinct from those of MORB. As a result, mixing models between MORB source and subducted sediment are tightly constrained in terms of the allowable proportion of sediment. Buffering of isotopic compositions together with considerable relative LILE enrichment might be achieved by mixing between mantle and a hydrous fluid which has equilibrated with not only sediment but also a large proportion of variably altered oceanic crust. High degrees of partial melting of mantle modified by a hydrous fluid reproduce the trace element pattern of the source in the derivative volcanic rocks and account for the depletion of HFSE and HREE relative to MORB.

• Research Organization: Souther Methodist Univ., Dallas, TX (USA)
• OSTI ID: 5064489
• Journal Information: Geochim. Cosmochim. Acta; (United States), Journal Name: Geochim. Cosmochim. Acta; (United States) Vol. 51:8; ISSN GCACA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580400* -- Geochemistry-- (-1989)
ALKALINE EARTH METALS
BARIUM
CHEMICAL COMPOSITION
CHEMISTRY
EARTH CRUST
EARTH MANTLE
ELEMENTS
GEOCHEMISTRY
GEOLOGIC MODELS
IGNEOUS ROCKS
ISLANDS
ISOTOPE RATIO
LANTHANUM
LEAD
LESSER ANTILLES
MAGMA
METALS
NEODYMIUM
OCEANIC CRUST
PETROCHEMISTRY
PETROGENESIS
PLATE TECTONICS
RARE EARTHS
ROCKS
STRONTIUM
SUBDUCTION ZONES
TECTONICS
TRACE AMOUNTS
VOLCANIC ROCKS
WEST INDIES