The ophiolitic rocks of the Attic-Cycladic crystalline belt are considered of key importance for ... more The ophiolitic rocks of the Attic-Cycladic crystalline belt are considered of key importance for understanding the Mesozoic tectonic evolution of the Aegean region. Unresolved questions concern their tectono-stratigraphic relationships across the region. The mode of occurrence of the Cycladic ophiolites varies, as they appear as: (a) dismembered blocks (olistoliths) within the supra-detachment units of Paros and Naxos; (b) mélange formations in the upper structural unit of western Samos and Skyros; and (c) meta-ophiolitic mélange in the Cycladic Blueschist Unit (CBU) from central Samos. The trace element geochemistry and Pb-Sr-Nd isotopes of the mafic ophiolitic rocks indicate four geochemical groups: (a) the upper unit metabasites from Paros and western Samos (Kallithea) display an evolved basaltic composition (Mg# 40.2–59.6), with low Zr/Nb values (5–16) and high Ce/Y values (1.3 to 2.6) compared to MORB, indicating island-arc tholeiite affinities; (b) Naxos upper unit metabasalts show spider diagrams patterns indicating ocean island basalt (OIB-type) affinities; (c) Central Samos metagabbros (CBU) are primitive rocks with Back-Arc Basin basalt affinities; (d) the Skyros metadolerites and Tinos (Mt Tsiknias) and S. Evia (CBU) metagabbros, cluster as a separate geochemical group; they exhibit high MgO values (>10 wt %), very low TiO2 values (0.1–0.2 wt %), Y and Yb, and depleted trace element N-MORB normalized patterns, similar to volcanic rocks formed in modern oceanic fore-arc settings, such as boninites. A combination of the Pb- and Sr-isotopic compositions of Cycladic metabasites indicate that the Pb and Sr incorporated in the Cycladic ophiolites correspond to mixtures of magmatic fluids with seawater (206Pb/204Pb = 18.51–18.80; 207Pb/204Pb = 15.59–15.7; 208Pb/204Pb = 39.03–39.80 and initial 87Sr/86Sr80 = 0.705–0.707). Furthermore, peridotite relicts from Samos, Paros, and Naxos—irrespective of the structural unit—display chemical affinities of ocean floor peridotites formed in a supra-subduction zone. The characteristics of harzburgite relicts in Cycladic serpentinites and Skyros indicate a highly residual nature of the mantle source. Geochemical data from this study shed further light on the complex structure of the oceanic lithosphere from which the Cycladic ophiolites originated.
Vlaykov VruhElshitsa represents the best example of paired porphyry Cu and epithermal CuAu depo... more Vlaykov VruhElshitsa represents the best example of paired porphyry Cu and epithermal CuAu deposits within the Late Cretaceous ApuseniBanatTimokSrednogorie magmatic and metallogenic belt of Eastern Europe. The two deposits are part of the NW ...
Vlaykov Vruh–Elshitsa represents the best example of paired porphyry Cu and epithermal Cu–Au depo... more Vlaykov Vruh–Elshitsa represents the best example of paired porphyry Cu and epithermal Cu–Au deposits within the Late Cretaceous Apuseni–Banat– Timok–Srednogorie magmatic and metallogenic belt of Eastern Europe. The two deposits are part of the NW trending Panagyurishte magmato-tectonic corridor of central Bulgaria. The deposits were formed along the SW flank of the Elshitsa volcano-intrusive complex and are spatially associated with N110-120-trending hypabyssal and sub-volcanic bodies of granodioritic composition. At Elshitsa, more than ten lenticular to columnar massive ore bodies are discordant with respect to the host rock and are structurally controlled. A particular feature of the mineralization is the overprinting of an early stage high-sulfidation mineral assemblage (pyrite ± enargite ± covellite ± goldfieldite) by an intermediate-sulfidation paragenesis with a characteristic Cu–Bi–Te–Pb–Zn signature forming the main economic parts of the ore bodies. The two stages of mineralization produced two compositionally different types of ores—massive pyrite and copper–pyrite bodies. Vlaykov Vruh shares features with typical porphyry Cu systems. Their common geological and structural setting, ore-forming processes, and paragenesis, as well as the observed alteration and geochemical lateral and vertical zonation, allow us to interpret the Elshitsa and Vlaykov Vruh deposits as the deep part of a high-sulfidation epithermal system and its spatially and genetically related porphyry Cu counterpart, respectively. The magmatic– hydrothermal system at Vlaykov Vruh–Elshitsa produced much smaller deposits than similar complexes in the northern part of the Panagyurishte district (Chelopech, Elatsite, Assarel). Magma chemistry and isotopic signature are some of the main differences between the northern and southern parts of the district. Major and trace element geochemistry of the Elshitsa magmatic complex are indicative for the medium-to high-K calc-alkaline character of the magmas. 87 Sr/ 86 Sr (i) ratios of igneous rocks in the range of 0.70464 to 0.70612 and 143 Nd/ 144 Nd (i) ratios in the range of 0.51241 to 0.51255 indicate mixed crustal–mantle
Ore-related structures at the Zn-Pb Mississippi Valley-type San Vicente deposit, Central Peru, di... more Ore-related structures at the Zn-Pb Mississippi Valley-type San Vicente deposit, Central Peru, display a systematic geometry with respect to bedding and a regional thrust, interpreted as Miocene in earlier studies. Sparry dolomite veins and breccia bodies have a constant NS direction, and are either perpendicular to bedding with dips ~70° to the east, or parallel to bedding, dipping ~25-30° westerly.
1D6partement de Min&alogie, Universit6 de Gen6ve, Rue des Maraichers 13, CH-1... more 1D6partement de Min&alogie, Universit6 de Gen6ve, Rue des Maraichers 13, CH-1211 Gen6ve 4, Switzerland 2Arica 343, Lima 9, Chorrillos, Peru Escuela de Geologia, Universidad Nacional de Ingenieria, Lima, Peru 3Institut de Min6ralogie, Universit6 de Lausanne, CH-1015 ...
... By contrast little is known about the genesis of the base metal prospects in southern Gaspé, ... more ... By contrast little is known about the genesis of the base metal prospects in southern Gaspé, although some studies of those prospects suggest a porphyry and/or skarn affinity (Williams-Jones, 1982; Roy, 1991; Malo et al., 1993; Moritz et al., 1993). ...
The ophiolitic rocks of the Attic-Cycladic crystalline belt are considered of key importance for ... more The ophiolitic rocks of the Attic-Cycladic crystalline belt are considered of key importance for understanding the Mesozoic tectonic evolution of the Aegean region. Unresolved questions concern their tectono-stratigraphic relationships across the region. The mode of occurrence of the Cycladic ophiolites varies, as they appear as: (a) dismembered blocks (olistoliths) within the supra-detachment units of Paros and Naxos; (b) mélange formations in the upper structural unit of western Samos and Skyros; and (c) meta-ophiolitic mélange in the Cycladic Blueschist Unit (CBU) from central Samos. The trace element geochemistry and Pb-Sr-Nd isotopes of the mafic ophiolitic rocks indicate four geochemical groups: (a) the upper unit metabasites from Paros and western Samos (Kallithea) display an evolved basaltic composition (Mg# 40.2–59.6), with low Zr/Nb values (5–16) and high Ce/Y values (1.3 to 2.6) compared to MORB, indicating island-arc tholeiite affinities; (b) Naxos upper unit metabasalts show spider diagrams patterns indicating ocean island basalt (OIB-type) affinities; (c) Central Samos metagabbros (CBU) are primitive rocks with Back-Arc Basin basalt affinities; (d) the Skyros metadolerites and Tinos (Mt Tsiknias) and S. Evia (CBU) metagabbros, cluster as a separate geochemical group; they exhibit high MgO values (>10 wt %), very low TiO2 values (0.1–0.2 wt %), Y and Yb, and depleted trace element N-MORB normalized patterns, similar to volcanic rocks formed in modern oceanic fore-arc settings, such as boninites. A combination of the Pb- and Sr-isotopic compositions of Cycladic metabasites indicate that the Pb and Sr incorporated in the Cycladic ophiolites correspond to mixtures of magmatic fluids with seawater (206Pb/204Pb = 18.51–18.80; 207Pb/204Pb = 15.59–15.7; 208Pb/204Pb = 39.03–39.80 and initial 87Sr/86Sr80 = 0.705–0.707). Furthermore, peridotite relicts from Samos, Paros, and Naxos—irrespective of the structural unit—display chemical affinities of ocean floor peridotites formed in a supra-subduction zone. The characteristics of harzburgite relicts in Cycladic serpentinites and Skyros indicate a highly residual nature of the mantle source. Geochemical data from this study shed further light on the complex structure of the oceanic lithosphere from which the Cycladic ophiolites originated.
Vlaykov VruhElshitsa represents the best example of paired porphyry Cu and epithermal CuAu depo... more Vlaykov VruhElshitsa represents the best example of paired porphyry Cu and epithermal CuAu deposits within the Late Cretaceous ApuseniBanatTimokSrednogorie magmatic and metallogenic belt of Eastern Europe. The two deposits are part of the NW ...
Vlaykov Vruh–Elshitsa represents the best example of paired porphyry Cu and epithermal Cu–Au depo... more Vlaykov Vruh–Elshitsa represents the best example of paired porphyry Cu and epithermal Cu–Au deposits within the Late Cretaceous Apuseni–Banat– Timok–Srednogorie magmatic and metallogenic belt of Eastern Europe. The two deposits are part of the NW trending Panagyurishte magmato-tectonic corridor of central Bulgaria. The deposits were formed along the SW flank of the Elshitsa volcano-intrusive complex and are spatially associated with N110-120-trending hypabyssal and sub-volcanic bodies of granodioritic composition. At Elshitsa, more than ten lenticular to columnar massive ore bodies are discordant with respect to the host rock and are structurally controlled. A particular feature of the mineralization is the overprinting of an early stage high-sulfidation mineral assemblage (pyrite ± enargite ± covellite ± goldfieldite) by an intermediate-sulfidation paragenesis with a characteristic Cu–Bi–Te–Pb–Zn signature forming the main economic parts of the ore bodies. The two stages of mineralization produced two compositionally different types of ores—massive pyrite and copper–pyrite bodies. Vlaykov Vruh shares features with typical porphyry Cu systems. Their common geological and structural setting, ore-forming processes, and paragenesis, as well as the observed alteration and geochemical lateral and vertical zonation, allow us to interpret the Elshitsa and Vlaykov Vruh deposits as the deep part of a high-sulfidation epithermal system and its spatially and genetically related porphyry Cu counterpart, respectively. The magmatic– hydrothermal system at Vlaykov Vruh–Elshitsa produced much smaller deposits than similar complexes in the northern part of the Panagyurishte district (Chelopech, Elatsite, Assarel). Magma chemistry and isotopic signature are some of the main differences between the northern and southern parts of the district. Major and trace element geochemistry of the Elshitsa magmatic complex are indicative for the medium-to high-K calc-alkaline character of the magmas. 87 Sr/ 86 Sr (i) ratios of igneous rocks in the range of 0.70464 to 0.70612 and 143 Nd/ 144 Nd (i) ratios in the range of 0.51241 to 0.51255 indicate mixed crustal–mantle
Ore-related structures at the Zn-Pb Mississippi Valley-type San Vicente deposit, Central Peru, di... more Ore-related structures at the Zn-Pb Mississippi Valley-type San Vicente deposit, Central Peru, display a systematic geometry with respect to bedding and a regional thrust, interpreted as Miocene in earlier studies. Sparry dolomite veins and breccia bodies have a constant NS direction, and are either perpendicular to bedding with dips ~70° to the east, or parallel to bedding, dipping ~25-30° westerly.
1D6partement de Min&alogie, Universit6 de Gen6ve, Rue des Maraichers 13, CH-1... more 1D6partement de Min&alogie, Universit6 de Gen6ve, Rue des Maraichers 13, CH-1211 Gen6ve 4, Switzerland 2Arica 343, Lima 9, Chorrillos, Peru Escuela de Geologia, Universidad Nacional de Ingenieria, Lima, Peru 3Institut de Min6ralogie, Universit6 de Lausanne, CH-1015 ...
... By contrast little is known about the genesis of the base metal prospects in southern Gaspé, ... more ... By contrast little is known about the genesis of the base metal prospects in southern Gaspé, although some studies of those prospects suggest a porphyry and/or skarn affinity (Williams-Jones, 1982; Roy, 1991; Malo et al., 1993; Moritz et al., 1993). ...
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