Composite synvolcanic intrusions associated with Precambrian VMS-related hydrothermal systems

Introduction and Geological Setting of the Iberian Pyrite Belt

“…Additionally, basaltic subvolcanic sills predate massive sulphides in Rio Tinto and Tharsis (Tornos et al 1998(Tornos et al , 2000, although in Aznalcóllar they occur beneath the massive sulphide deposits and therefore a link was suggested between mafic volcanism and VHMS deposits as possible in Aznalcóllar Sáez et al 1999). In fact, in other VHMS belts there are massive sulphide deposits interpreted as formed by magmatic-hydrothermal fluids derived from subvolcanic felsic igneous complexes accompanied by mafic-ultramafic rocks (Galley 2003;Díez-Montes and Bellido-Mulas 2008). An alternative to the magmatic contribution to the hydrothermal seawater fluid could be metamorphic or crustal fluids (Sánchez-España et al 2003;Moura 2005).…”

Regional setting and characteristics of the Neoproterozoic Wadi Hamama Zn–Cu–Ag–Au prospect: evidence for an intra-oceanic island arc-hosted volcanogenic hydrothermal system

“…Using the classification criteria for tonalite-trondhjemite suites of Barker and Arth (1976), the TTP is classified as a low-alumina (<15 wt%) intrusion. This type of intrusions is formed within the oceanic arc extensional zone due to low-pressure partial melting or fractional crystallization (Galley 2003). The bimodal nature of the WH area hypothesizes the low-pressure partial melting of the tholeiitic basalt to form these three assemblages.…”

“…As the porphyritic granite dykes intruded both the altered and the volcaniclastic hanging wall sequence the WH prospect, the candidate intrusions that may be responsible for hydrothermal convection could be the dacite, TTP or the quartz-diorite intrusion. The subvolcanic intrusions, which act as heat engines, are characterized by the lack of significant metamorphic aureole due to the convective heat transfer during crystallization (Cathles et al 1997) and by the presence of fracture-controlled alteration assemblages within the intrusions (Galley 2003). These two features characterize both the dacite and the TTP, but not the quartz-diorite stock.…”

“…These intrusions have been interpreted as possible heat engines, which drive the mineralizing hydrothermal systems (Galley 2003). As the porphyritic granite dykes intruded both the altered and the volcaniclastic hanging wall sequence the WH prospect, the candidate intrusions that may be responsible for hydrothermal convection could be the dacite, TTP or the quartz-diorite intrusion.…”

Structural, textural, geochemical and isotopic signatures of synglaciogenic Neoproterozoic banded iron formations (BIFs) at Bafq mining district (BMD), Central Iran: The possible Ediacaran missing link of BIFs in Tethyan metallogeny

“…The green color of the actinolite is a reflection of the high iron content of the mineral and probably of ferroactinolite group. Similar actinolites have been reported to form at temperatures of 350-450º C in exhalative ore deposits (Galley, 2003). Chlorites form greenish euhedral, radiating and stretched crystals.…”