Whole-rock geochemistry of some tonalite and high Mg/Fe gabbro, diorite, and granodiorite plutons (sanukitoid suites) in the Kuhmo district, eastern Finland

Abstract

New whole-rock geochemical analyses (major and trace elements) of three tonalite plutons and high Mg/Fe granodiorites and diorites, termed sanukitoid suites, are presented from Neoarchaean Kuhmo district, eastern Finland. The 2.83 Ga and 2.78 Ga tonalites display only moderate fractionation of LREE/HREE thus demanding only minor or no residual garnet in their respective source regions. However, the more prominent HREE depletion in the 2.75 Ga tonalites requires more significant garnet residue. The relatively wide compositional variation in the tonalites implies that Archaean TTG (tonalite-trondhjemite-granodiorite) magmatism was derived in general from sources that exhibited considerable mineralogical heterogeneity. The ~2.70 -2.74 Ga high-Mg/Fe granodiorites and diorites are characterised by strong fractionation of LREE/HREE, relatively high Ba and Sr, and elevated abundances of Cr and Ni as well systematic depletions in P and Ti, which are all typical features of Archaean sanukitoid suites. Some of the granodiorite plutons contain compositionally intermediate high-K enclaves, which share these geochemical characteristics, implying a contribution of mafic-intermediate LILE-and LREE-enriched source for the magma. The geochemical characteristics of the studied plutonic rocks demonstrate the role of contrasting sources for the tonalites and sanukitoid suites in the Kuhmo district.

Geochemical and Nd isotope constraints on petrogenesis of granitoids from NW part of the eastern Dharwar craton: Possible implications for late Archaean crustal accretion

“…However, compared to Archaean TTG rocks of some other cratons (e.g. Condie, 1981Condie, , 2005Kapyaho, 2006;Whalen et al, 2004a) they show markedly higher enrichments of LILE (Rb, Ba, U, K and La).…”

Age and isotopic geochemical characteristics of Archean carbonatites and alkaline rocks of the Baltic shield

“…Granulite-facies metamorphism is dated at 2.70-2.62 Ga. (3) The outer zone is formed by an array of 'younger' granite bodies (2.69-2.58 Ga) and local manifestations of granulite-facies metamorphism. Thus, the main development trend was rapid expansion of the area [Mints, 2015a, based on data of [Bibikova et al, 1996[Bibikova et al, , 2005Halla, 2002Halla, , 2005Heilimo et al, 2007;Käpyaho, 2006;Mutanen, Huhma, 2003;Lobach-Zhuchenko et al, 1993Lobach-Zhuchenko, Chekulaev, 2007;Samsonov et al, 2004].…”

Age and petrology of the Kaapinsalmi sanukitoid intrusion in Suomussalmi, eastern Finland

“…Taylor & McLennan, 1985). Kaapinsalmi sanukitoid data from Heilimo (2006b); Arola, Loso, Siikalahti sanukitoids analyses after Käpyaho (2006); Nilsiä and Koitere data from Halla (2005); Western sanukitoid zone data from Lobach-Zhuchenko et al (2005) and Eastern Finland TTG patterns after Martin (1987).…”

“…Granitoids of the Kianta terrain are metamorphosed, but they have preserved their magmatic texture. Käpyaho et al (2006) and Käpyaho (2006) have divided the Kianta granitoids into three magmatic episodes: 1) TTG-granitoids 2.83 -2.74 Ga, 2) sanukitoids 2.74 -2.70 Ga and 3) leucocratic granites and granodiorites 2.70 -2.68 Ga.…”

“…Sanukitoid intrusions in the Russian part of the Karelian craton are divided into Eastern and Western sanukitoid zones, which differ in composition and age (�obach-Zhuchenko et al, 2005;Bibikova et al, 2005). Seven sanukitoid intrusions located in Finland have been described: Kuittila (O'Brien et al, 1993), Nilsiä, Koitere (Halla, 2005), Arola, �oso, Siikalahti Käpyaho 2006) and the recently recognised Kaapinsalmi sanukitoid intrusion (Heilimo, 2006a;2006b) (Fig. 1).…”