The Granitis area in the Southern Rhodope Massif (Greece) hosts a previously undocumented intrusion-related hydrothermal system characterized by systematic proximal-to-distal metal zoning surrounding the 32-26 Ma Granitis intrusion. The Granitis intrusion is a composite pluton consisting of quartz monzonite-granodiorite, quartz monzonite, and syenitic lithologies, with abundant monzodioritic enclaves. It is a metaluminous, high-K calcalkaline to shoshonitic intrusion interpreted to have evolved through fractional crystallization accompanied by episodic mafic magma mingling. Al-in-hornblende barometry indicates crystallization pressures of 5.0-7.0 +/- 1.0 kbar, recording magma storage at mid- to lower-crustal depths, whereas biotite geobarometry indicates shallow solidification pressures of approximately 0.8-0.9 +/- 0.3 kbar. Whole-rock Fe2O3/FeO ratios (0.6-0.7) and Fe-Ti oxide mineral chemistry, including Mn-rich ilmenite coexisting with magnetite, indicate transitional to reduced magmatic conditions and place the intrusion near the magnetite-ilmenite series boundary. Mineralization occurs in three principal styles: (1) intrusion-hosted Bi-W-Sn-Te-Au vein systems that are strongly overprinted by supergene oxidation; (2) proximal marble-hosted reduced skarns and hydrothermal breccias containing pyrrhotite, molybdenite, cassiterite, and geikielite; and (3) distal Mn-Ag-Zn-Pb mineralization developed within the surrounding carbonate sequence. The distal system records a multistage evolution from early Mn silicate-carbonate-sulfide assemblages (rhodonite-rhodochrosite-alabandite-pyrite-galena-hessite-argentite) to late-stage Mn oxide mineralization. Bulk-ore geochemistry reveals significant enrichment of metals within Mn oxides, particularly Ag (up to 2556 ppm), together with Zn, Pb, Au, Bi, Mo, and W. The Granitis hydrothermal system exhibits a coherent proximal-to-distal metal zonation pattern, forming the basis of a conceptual exploration model that links intrusionhosted, skarn, and distal Mn-Ag-Zn-Pb mineralization. This zonation reflects the progressive physicochemical evolution of hydrothermal fluids and demonstrates the capacity of Mn oxides to adsorb, concentrate, and retain metals transported during the late stages of hydrothermal activity. These results indicate that hydrothermal Mn mineralization can serve as a distal exploration vector toward concealed fertile intrusions and their associated mineralized systems. By integrating intrusion petrology, magmatic redox conditions, mineral chemistry, and ore geochemistry, this study provides new insights into metal distribution patterns and exploration vectors within intrusion-related hydrothermal systems in the Southern Rhodope Massif.
Geochemical and mineralogical characterization of the Granitis intrusion-related hydrothermal system, northern Greece: Implications for metal zoning and exploration
Konstantinos Mavrogonatos;
2027-01-01
Abstract
The Granitis area in the Southern Rhodope Massif (Greece) hosts a previously undocumented intrusion-related hydrothermal system characterized by systematic proximal-to-distal metal zoning surrounding the 32-26 Ma Granitis intrusion. The Granitis intrusion is a composite pluton consisting of quartz monzonite-granodiorite, quartz monzonite, and syenitic lithologies, with abundant monzodioritic enclaves. It is a metaluminous, high-K calcalkaline to shoshonitic intrusion interpreted to have evolved through fractional crystallization accompanied by episodic mafic magma mingling. Al-in-hornblende barometry indicates crystallization pressures of 5.0-7.0 +/- 1.0 kbar, recording magma storage at mid- to lower-crustal depths, whereas biotite geobarometry indicates shallow solidification pressures of approximately 0.8-0.9 +/- 0.3 kbar. Whole-rock Fe2O3/FeO ratios (0.6-0.7) and Fe-Ti oxide mineral chemistry, including Mn-rich ilmenite coexisting with magnetite, indicate transitional to reduced magmatic conditions and place the intrusion near the magnetite-ilmenite series boundary. Mineralization occurs in three principal styles: (1) intrusion-hosted Bi-W-Sn-Te-Au vein systems that are strongly overprinted by supergene oxidation; (2) proximal marble-hosted reduced skarns and hydrothermal breccias containing pyrrhotite, molybdenite, cassiterite, and geikielite; and (3) distal Mn-Ag-Zn-Pb mineralization developed within the surrounding carbonate sequence. The distal system records a multistage evolution from early Mn silicate-carbonate-sulfide assemblages (rhodonite-rhodochrosite-alabandite-pyrite-galena-hessite-argentite) to late-stage Mn oxide mineralization. Bulk-ore geochemistry reveals significant enrichment of metals within Mn oxides, particularly Ag (up to 2556 ppm), together with Zn, Pb, Au, Bi, Mo, and W. The Granitis hydrothermal system exhibits a coherent proximal-to-distal metal zonation pattern, forming the basis of a conceptual exploration model that links intrusionhosted, skarn, and distal Mn-Ag-Zn-Pb mineralization. This zonation reflects the progressive physicochemical evolution of hydrothermal fluids and demonstrates the capacity of Mn oxides to adsorb, concentrate, and retain metals transported during the late stages of hydrothermal activity. These results indicate that hydrothermal Mn mineralization can serve as a distal exploration vector toward concealed fertile intrusions and their associated mineralized systems. By integrating intrusion petrology, magmatic redox conditions, mineral chemistry, and ore geochemistry, this study provides new insights into metal distribution patterns and exploration vectors within intrusion-related hydrothermal systems in the Southern Rhodope Massif.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
