Petrology and K-Ar ages of rift-related basaltic rocks, offshore northern Brazil, 3/sup 0/N

Journal Article · Tue Jul 01 00:00:00 EDT 1986 · J. Geol.; (United States)

OSTI ID:7063118

Fodor, R V; McKee, E H

Tholeiitic basaltic rock in three cores from Petrobras drill site APS-21, 1960-2480 m depths, Amapa basin, offshore Brazil is compositionally similar to rift-related basaltic rock associated with the opening of both the North and South Atlantic Oceans (SiO/sub 2/ 52-54 wt %; K/sub 2/O 0.7-1.3%; TiO/sub 2/ 1.3-2%). Whole-rock K-Ar ages are 185.4, 183.2, and 126.5 m.y. If these represent crystallization ages, then the older samples correspond to North Atlantic tectonism (as represented by the Liberian dike system) and the younger correlates with South Atlantic rift-related magmatism (of which Serra Geral flood basalts are the best example). Trace- and REE-elements identify T-type mantle source-areas (La/Sm/sub (n)/ approx. 2; Zr/Nb 8-11) that feasibly were mixes of N-type and P-type components (metasomatized or veined upper mantle). These Amapa basin mafic rocks document the southernmost magmatism related to North Atlantic rifting, as well as early Mesozoic mantle source-areas and processes beneath Gondwanaland such as those identified with basalts in the South Atlantic basin.

• Research Organization: North Carolina State Univ., Raleigh
• OSTI ID: 7063118
• Journal Information: J. Geol.; (United States), Vol. 94
• Country of Publication: United States
• Language: English

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