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- A novel conceptual model of intrusion related gold bearing systems and
exploration tools
Authors: Eugen Orlandea et al.
Abstract: Despite numerous debates conducted in the last two decades, the concept of intrusion related gold systems IRGS remains controversial and sometimes befuddling. The key issue drifts from case to case, i.e., initial to subsequent proposed classifications, presence of gold in reduced fluids-porphyritic environments, non-porphyry gold in orogenic terrains and participation of non-magmatic gold fluids in depositional processes. Trying to avoid atypical or particular aspects of certain deposits, a genuine metallogenetic depiction intends to enhance the intrusion related systems meaning. Gold is either a major constituent or a mere byproduct. A vertical metal zonation develops from surface to depth: Au, Ag → Cu, Pb, Zn → Cu, Au → Cu, Mo (Au), W → Fe, Cu, Au (Co,W) → U, Ce, La. Whether the relationship between different intrusion related occurrences is well known at shallow depth (epithermal, mesothermal, porphyry), so far less knowledge and understanding is assigned to deep seated mineralization (porphyry, Iron Oxides- Copper-Gold/IOCG). A specific relationship between those two deep seated ore styles emerges, that is the IOCG, confined to magmatic-hydrothermal type, is situated in the root zone of a deep porphyry system. Complementary information about updated classic exploration tools encompasses specifically geochemical association, geophysical signature, key alteration minerals, Au/Ag ratio and, last but not least, type minerals that contain/include gold in each intrusion related environment. A further valuable tool is given by the estimate of Au grade range specific to each gold bearing mineral sample in shallow or deep seated setting.
PubDate: Wed, 12 Feb 2020 12:36:54 PST
- Monographic study of the Late Cretaceous representatives of the
bolivinoidid benthic foraminifera
Authors: Marius Dan Georgescu
Abstract: A high resolution taxonomy and classification framework is developed for the representatives of the calcareous benthic foraminiferal family Bolivinoididae; this family consists of 24 species assigned to three genera. This new classification includes data pertaining of the test ultrastructure, ornamentation and porosity, which are obtained with the aid of careful and extensive study of the specimens under the scanning electron microscope. Two new taxa are described: Bolivinoides antiquum – n. sp. and Swiecickina – n. gen. A biostratigraphical framework consisting of eleven biozones based on bioevents given by species of the genera Bolivinoides and Swiecickina is developed for the middle Santonian-Maastrichtian stratigraphical interval; its resolution is more than double when compared to those of the previously developed biostratigraphical frameworks based on the representatives of this group.
PubDate: Fri, 13 Apr 2018 12:55:50 PDT
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