HEAVY MINERALS OF THE INNER CONTINENTAL SHELF OFFSHORE THE AÇU RIVER'S DELTA (NORTHEASTERN BRAZIL)

HELENICE VITAL, INGRED M. GUIMARÃES GUEDES

Resumo


Provenance and sediment dispersal has been investigated in the northeastern Brazil. Most precisely on the inner continental shelf offshore the Açu river's delta (Rio Grande do Norte State). The heavy mineral assemblages delineated along the inner shelf faithfully reflect the various petrographic units of the source area. The distribution patterns of the principal heavy minerals indicate the major point sources of sediment supply onto the shelf and reveal intensive mixing, sorting processes and that an westerly (from east to west) longshore current plays an important role in the sediment dispersal. As a result, the mineral distribution east of the Açu River is rich in stable heavy minerals (mainly zircon and tourmaline) whilst west of the Açu River is rich in unstable ones (mainly hornblende and epidote). A mixing zone occur in front of the river where stable and unstable minerals are present. In addition to provenance-induced variability, mineralogical differences between E and W provinces could indicate that environmental processes have contributed to the total variability of the inner continental shelf sediments.

Palavras-chave


Heavy minerals; Provenance; Sediment dispersal; Brazil; Northeastern continental shelf.

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