Microfacies studies of carbonate rocks from Jurassic outcrops in the north of Faro, Southern Portugal

The Middle and Upper Jurassique limestones investigated were sub-divided into nine microfacies (MF) types. The firsts four represent Bathonian sediments with shallow water characteristics typical for carbonate platforms. They are comparable with Wilson's facies zones 6 to 8. Reef and reef debris, near-shore clastic-dominated limestones are not present. These MF-types are reiterated several times without cyclicity. The vertical development of the differentiated facies units indicates a close interfingering. The microfacies data are typical of inter to shallow subtidal environments; both authigenous quartz and low faunal and floral diversity of several layers point to temporary restricted conditions. The occurrence of Dictyoconus cayeuxi LUCAS and Callovian ammonites from the above lying strata argue for a Bathonian age. The MF-types 5-9 (Oxfordian-Kimmeridgian) show completely different sedimentation conditions. Fully marine nearshore recifal limestones alternate with pelagic sediments formed at deeper shelf areas. The pelagic micritic limestones of Oxfordian age are characterized by allodapic intercalations whereas the Oxfordian/Kimmeridgian limestones with tuberolithic fabrics often show intensive silifications. Only initial patch reef growth-stages were reached during the development of the Oxfordian and Kimmeridgian shallow water limestones.

Origem, transporte e deposição do ouro em Manica (Moçambique)

The different types of Archean gold deposits in the Manica greenstone belt of western Mozambique are briefely describcd in the context of their geological setting. Particular attention is devoted to the mineralogy, petrology, geological controls, refractoriness to treatment and prospection of these gold deposits. The genesis of gold was stratigraphically controled, but structural and metamorphic events related to the intrusion of late granites have concentrated and relocated the gold in different geological environments. The possibility of additional gold occurences in different rocks sequences is discussed as well as possible guidelines for future research and development.

The marine Neogene of Eastern Venezuela : a preliminary report

Proceedings of tile 1" R.C.A.N.S. Congress, Lisboa, October 1992