Abstract
The strata-bound fluorite-(barite-)Pb-Zn ore deposits occurring within the more than 3,000 m thick Alpujarride Carbonate Formation of the Betic Cordillera, southern Spain, are linked to two defined stratigraphic positions (within the Anisian and at the Ladinian-Carnian transition) and to definite sedimentary contexts. These are highly restricted lagoons isolated from the open sea by calcarenitic barriers with noticeable development of algal mats in their inner margins. Preevaporitic deposition conditions are usually recognized. The ore-bearing horizons are located either at the transition from evaporitic to normal marine deposition (as in the case of the Anisian ore-bearing horizon) or at the transition from normal marine to evaporite deposition (as in the case of the uppermost Ladinian to lowermost Carnian ore-bearing horizon). These vertical facies changes correspond also to the transitions from predominantly terrigenous (continental and/or coastal) sedimentation to marine carbonate sedimentation (Anisian ore deposits) and vice versa (upper Ladinian-lower Carnian). It is proposed that the ore deposits in the Triassic Alpujarride Formation are controlled by certain facies associations in the lagoonal environment. The depositional environment determines the hydrologic regimes responsible for early diagenetic formation of fluorite and of the related ore minerals in a way similar to that of early-diagenetic dolomite. This hypothesis is consistent with field and petrographic observations and with available geochemical and itotopic data reported in other works. The present investigation intends to underline the role played by surface-linked ore formation processes, i.e., by ore-forming processes essentially linked to the environments in which sedimentation and early diagenesis takes place, in the genesis of numerous strata-bound Zn-Pb-(F-Ba) ore deposits in carbonate rocks.
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