Petrogenesis of the Late Cenozoic volcanics of Hispaniola

Conference · Tue Jan 01 04:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6070079

Vespucci, P D

Late Cenozoic volcanic rocks of Hispaniola are subdivided into two geochemically contrasting series, a mafic alkaline series (MA-series) and a calc-alkaline series (CA-series). MA-series basalts show slight to moderate silica undersaturation, high TiO/sub 2/ and MgO contents and moderately high total alkalis. MA types are strongly enriched in K, Rb, Sr, Ba, U, Th and LREEs with Ba/La ratios of 0.98. REE patterns are highly fractionated (La/sub n//Yb/sub n/ ratios = 62, and La/sub n//Sm/sub n/ ratios = 6.3). HFS elements Zr, Hf, Nb and Ta are high resembling intraplate basalts. 87Sr/86Sr ratios are high (.7059 to .7079) with low Rb/Sr ratios (.03 to .15). The basalts, basaltic andesites, trachyandesites and dacites of the CA-series show lower TiO2 and MgO contents and moderately high total alkali contents. Strong enrichment is seen in K, Rb, Sr, Th, U and LREEs with Ba/La ratios as high as 5.6. REE patterns are fractionate to a lesser degree compared to the MA-series (average La/sub n//Yb/sub n/ = 23.4, and La/sub n//Sm/sub n/ ratios less than 5). HFS elements are lower resembling typical island arc types. CA-series show lower 87Sr/86Sr ratios (.7043 to .7053), with similarly low Rb/Sr ratios as seen in the MA-series. The MA-series and CA-series must have two separate primary sources as constrained by isotopic and trace element differences. Suggested models involve multi-stage, multi-component petrogenesis. Enrichment of depleted sub-arc mantle by a metasomatic melt fluid followed by second stage partial melting and final fractional crystallization are the principle elements of the preferred model.

• Research Organization: George Washington Univ., Washington, DC (USA)
• OSTI ID: 6070079
• Report Number(s): CONF-8510489-
• Conference Information: Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580300* -- Mineralogy
Petrology
& Rock Mechanics-- (-1989)
580400 -- Geochemistry-- (-1989)
ALKALINE EARTH ISOTOPES
CENOZOIC ERA
CHEMICAL COMPOSITION
CHEMISTRY
CRYSTALLIZATION
GEOCHEMISTRY
GEOLOGIC AGES
GEOLOGIC MODELS
GREATER ANTILLES
HISPANIOLA
IGNEOUS ROCKS
ISLANDS
ISOTOPES
PETROGENESIS
PHASE TRANSFORMATIONS
QUATERNARY PERIOD
ROCKS
STRONTIUM ISOTOPES
VOLCANIC ROCKS
WEST INDIES