Κυριακή, 16 Ιουλίου 2017

The X-MINE project re-considers ore deposit modeling, and re-assesses the exploration and economic geology potential of Bergslagen

The historical and classical mining province of Bergslagen in Sweden remains a potential exploration target. New metallogenetic interpretations, 3D/4D geological modeling, performance of advanced multidisciplinary methodologies and innovative technology applications may generate further challenging opportunities in terms of locating deeper seated ore bodies and unlock feasible critical raw materials associations. A major mineralised belt is the one defined, from north to south, by the well known mines and occurrences in Stråssa, Håkansboda, Lovisa, Stripa, Guldsmedshyttan, Fanthyttan and Leja. A regional scale N20-40oS striking shear zone, imposed upon a lithostratigraphic sequence of acidic metavolcanic rocks interbedded with horizons of crystalline carbonates, seems to be the main structure controlling the spatial extension, and most probably the oxide and sulfide ore forming mechanism in the area.  Shear-related ductile and brittle deformation appears more likely to be the reason for the origin of the banding, folding and fracturing observed. Up to now the genetic origin of the mineralizing processes and ore forming systems were referred to either sedimentary exhalative (SEDEX), mainly due to the occurrence of Banded Iron Formations (BIF), and/or to carbonate replacement skarn-related deposition.

Major questions and issues to be highlighted and addressed, particularly as part of the recently started EU-funded X-MINE project, are:
·        The presence of SEDEX mineralisations and they relate timely to ore formation
·        The role of shear-zone deformation in controlling mineralizing fluids and ore deposition in relation to the metavolcanic and interbedded marble contact zones
·        The role of carbonate/marble beds in the formation of skarn/manto-style deposits
·        The role of crosscutting fault systems and their intersections with shear zone and carbonate rocks in forming ore concentrations
·        The identification and characterisation of alteration processes in relation to mineralisations, based on both mineralogy and lithogeochemistry
·        A better understanding of why various types of mineralisations, in terms of mineralogical and geochemical composition, are formed and found in different locations and parts within a pretty similar setting of bedrock lithologies, though strikingly controlled alongside the shear-zone structure and carbonate rocks lithostratigraphy, such as,
o   Iron ore in Stråssa 
o   Cu, Co, As, Sb, Au, Bi in Håkansboda
o   Zn, Pb in Lovisa
o   Iron ore in Stripa
o   Ag, Pb in Guldsmedshyttan
o   Cu,… in Leja
·        How is this part of the belt, ore geologically connected and linked to its northward extension towards Bastnäs and Norberg, where also a potential REE component is added to the mineral system, to form the so called REE-line  
·        Finally which is the role of the granitic, but also the metamafic intrusions in sourcing heat, mobilizing hydrothermal fluids and providing metals













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