Cuencas Petroliferas De Venezuela
Located on thesouthern border of the Eastern Venezuela basin. Estudio geoquirnico en la Cuenca Oriental y Faja Petrolifera de Venezuela. INTEVEP, S.A.
. 136 Downloads.AbstractUltramafic-hosted deposits of magnesite (MgCO 3) have been studied on Margarita Island, Venezuela, to elucidate the source of carbon and conditions of formation for this type of ore. Petrographic, mineralogic, and δ 18O data indicate that magnesite precipitated on Margarita in near-surface environments at low P and T. Δ 13C ranges from −9 to −16‰ PDB within the magnesite and −8 to −10‰ PDB within some calcite and dolomite elsewhere on the island. The isotopically light dolomite fills karst and the calcite occurs as stock-work veins which resemble the magnesite deposits. These carbon isotopic ratios are consistent with a deep-seated source rather than an overlying source from a zone of surficial weathering. However, there is not much enrichment of precious metals and no enrichment of heavy rare-earth elements, as would be expected if the carbon had migrated upward as aqueous carbonate ions.
Cuencas Petroliferas De Venezuela Maracaibo Falcon
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The carbon probably has risen as a gaseous mixture of CO 2 and CH 4 which partially dissolved in near-surface water before leaching cations and precipitating as magnesite and other carbonates. The process probably is ongoing, given regional exhalation of carbonaceous gases.