Postorogenic alkali feldspar granite and associated pegmatites in West Avalonia: the petrology of the Neoproterozoic Georgeville Pluton, Antigonish Highlands, Nova Scotia

Abstract

The 579.8 ± 2.2 Ma ( 40 Ar-39 Ar, muscovite) Georgeville Pluton in mainland Nova Scotia is an epizonal body consisting of alkali feldspar granite and related pegmatite. The pluton intrudes the ca. 619-608 Ma arc-related rocks of the Georgeville Group, which comprises part of West Avalonia, the largest terrane in the Canadian Appalachians. The granite is characterized by above-average SiO 2 , Th, Nb, Y, and Zr; very low CaO, TiO 2 , MgO, FeO, and MnO; and most notably by positively sloped rare earth element (REE) profiles generated by extreme light REE depletion. Tectonic discrimination diagrams suggest a within-plate environment, with many, but not all, geochemical and mineralogical features resembling A-type granites. Numerous local and regional geological constraints indicate that the pluton was intruded in a trancurrent setting following the cessation of Neoproterozoic arc-related magmatism along the West Avalonian portion of the Gondwanan continental margin. Geochemical data are consistent with derivation by partial melting of depleted crust or upper mantle followed by extreme fractionation, including REE-rich accessory phases.

Age and tectonic setting of Neoproterozoic granitoid rocks, Antigonish Highlands, Nova Scotia, Canada: implications for Avalonia in the northern Appalachian orogen

“…Some mineralogical and chemical features resemble those of A-type, within-plate granite. Muscovite yielded a 40 Ar/ 39 Ar plateau age of 579.8 6 2.2 Ma, interpreted by Murphy et al (1998) as the age of intrusion. The unique mineralogy associated with the granite and associated niobium-yttriumfluorine-type pegmatite dykes (e.g., amazonitic microcline, topaz, Hf-rich zircon, with minor ferrocolumbite and polycrase) have been studied previously (e.g., Hay 2001;Anderson et al 2008;Dalby et al 2010).…”

“…The Georgeville Pluton (Murphy et al 1998) or Georgeville Granite (Anderson et al 2008) is a small (ca. 1.5 km across) epizonal body that is exposed along the shoreline northeast of the Greendale Plutonic Suite.…”

Investigation of Feldspar Raw Material Potential of Alkali Feldspar Granites and Alkali Feldspar Syenites Within Central Anatolia

“…The major oxide % element contents of alkali feldspar granite and alkali feldspar syenites examined in the study are given in table 3. The results of the geochemical analysis were interpreted by comparing with some of the alkaline feldspar granites in the literature (Junggar-Mongolia, Changyi-China, Alvand-Iran, Katharina-Egypt, Scotland, Klipberg-Africa) (Table 4) (Data were taken from Scheepers and Schoch, 1988;Murphy et al, 1998;Katzir et al, 2007;Geng et al, 2009;Aliani et al, 2011;Lan et al, 2015).…”