Mantle plumes, associated intraplate tectonomagmatic processes and ore systems

Abstract

Intraplate tectonic and magmatic phenomena are linked to deep mantle plumes and asthenospheric upwellings. Resulting magmas, which include layered mafic-ultramafic intrusions, sill complexes, continental and oceanic flood lavas, giant dyke swarms and anorogenic A-type granitic rocks, are responsible, directly or indirectly, for a large number of intraplate and anorogenic ore systems. These ore systems can be considered in terms of 1) magma-associated, such as orthomagmatic Ni-Cu-PGE, Cr in mafic-ultramafic rocks and magmatichydrothermal ore systems in anorogenic A-type magmas (e. g. greisen Sn-W, Fe oxide-Cu-Au); and 2) hydrothermal systems powered by the large thermal energy that results from the emplacement of plume-derived melts into the crust. These hydrothermal ore systems include lowS epithermal, porphyry, VMS and Carlin style deposits. Campbell and Davies (2006 and references therein) and Campbell (2005) discussed the mantle plume hypothesis. Here I provide an overview of mantle plumes with some emphasis on associated tectonic and magmatic processes, in order to set the background for those ore systems that are linked to these mantle processes. Tectonic, magmatic and geomorphological effects of mantle upwellings are summarised in Table 1 (Pirajno, 2004a). Ore systems that are directly or indirectly linked with mantle processes are discussed in the next section. Mantle plume activities in the geological record are comprehensively treated in Ernst and Buchan (2003)

Vanadium bearing titaniferous magnetite ore bodies of Ganjang, Karbi-Anglong District, Northeastern India

“…Alkaline-carbonatite magmatism and associated Vanadium bearing titaniferous magnetite mineralization can be attributed to a complex interplay of several tectonomagmatic processes (Gaspar and Wyllie, 1983;Piranjo, 2007;Reguir et al 2008). The occurrence and geological relationships of Ganjang vanadium bearing titaniferous magnetite ores indicate that their genesis is intimately related to fractional crystallization processes that were responsible for the formation of their silicate host rocks as it has been documented from Bushveld Complex (Reynolds, 1985).…”

“…A wide range of ore-forming processes are known to be related to the mechanism of intracontinental rifting and the resulting alkaline-carbonatite magmatism (Piranjo, 2007).The various processes of magmatic differentiation operating in a fluid enriched environment, sometimes aided by metasomatic effects on the parent melt, favour intrusions of alkaline-mafic-ultramafic rocks and carbonatites. This is accompanied by late stage enrichment of elements like Ti, V, Fe, Mn, Zr, Ni, Co, Cr, Cu etc.…”

“…Titanium, Vanadium and Fe oxides are generally derived from magmas that are richer in Fe, Ca and alkali. Economically important, orthomagmatic, vanadium bearing titaniferous magnetite ores are formed by late stage segregation from volatile rich, differentiated alkaline magmas triggered by episodic increases in fO 2 (Piranjo, 2007). The present article reports for the first time the occurrence of orthomagmatic vanadium pyroxenite and alkali gabbro.…”

Magmatic sulfide-rich nickel-copper deposits related to picrite and (or) tholeiitic basalt dike-sill complexes: A preliminary deposit model

“…Although magmatic activity in LIPs can have lifespans of 50 million years (Myr) or more, the largest proportion ( greater than 75 percent) of the total igneous volume is generally emplaced during a short duration pulse(s) of approximately 1 to 5 Myr (Courtillot and Renne, 2003;Bryan and Ernst, 2008). The emplacement of such large volumes of mafic and ultramafic magma is attributed to the rise and impingement of mantle plumes on continental and oceanic lithospheric plates (Condie, 2001;Pirajno, 2007).…”

“…Extension, rifting, and development or reactivation of deeply penetrating faults typically accompany development of LIPs and play an important role in providing zones of weakness and dilation along which magma may ascend into the crust (Pirajno, 2007). These magma-focusing structures facilitate development of dynamic subvolcanic feeder systems that typically host sulfide-rich Ni-Cu±PGE deposits (Arndt, 2005).…”