This Archaean greenstone belt is predominantly composed of tholeiitic basalt
lava and volcaniclastic deposits, ultramafic rocks, felsic volcanic rocks and sediments surrounded by younger Archaean granitoids.
The western segment is dominated by a thick sequence of tholeiitic basalt
with common BIF units, typical of the Southern Cross Granite Greenstone Terrane (Wyche, 1999).
The Cuillin centre is a composite confluent intrusion ranging in composition from peridotite to gabbro (Stuart et al., 2000) Although they post-date most basalts, the Cuillin intrusive complex is most likely coeval with the latest Skye Main Lava Series tholeiitic basalt
Kaersutite phyric tholeiitic basalt
The 1970 sample from the northwestern knoll is transitional basalt, plotting on the Hawaiian tholeiite-alkalic basalt boundary, whereas the 1994 lava is tholeiitic basalt
with a higher Si[O.sub.2] content (Fig.
Geochemical systematics of tholeiitic basalt
from the 2.7 Ga Ramagiri-Hungund composite greenstone belt, Dharwar craton.
The northwestern part of the island consists of early Jurassic tholeiitic basalt
(Trembath 1973; Wade et al.
2) 2.88-2.74 Ga--deposition of sequences of tholeiitic basalt
, komatiite, felsic turf, iron formation, and abundant clastic sedimentary rocks, accompanied by the emplacement of voluminous, synvolcanic tonalite-trondhjemite plutonic suites and coeval deformation.
This is overlain by voluminous tholeiitic basalt
and minor komatiite (2740-2700 Ma), probably indicating rifting and/or plume activity, at a scale comparable to that of modern large igneous provinces.
Different geochemical studies on the rocks of the Arquia Complex reveal an oceanic origin from tholeiitic basalts
in MORB or N-MORB environments types (Villagomez et al., 2011; Rodriguez and Arango, 2013; Ruiz et al., 2012).
This intercratonic area, including the westernmost fringe of the Parana Basin (PB), represents an undeformed basin along the western Gondwana (Figure 1), where the sedimentation, started in Cambrian times, was topped by Early Cretaceous tholeiitic basalts
of the Serra Geral Formation [8, 9] and followed by younger sedimentation (Figure 2).
Otherwise, the presence of alkaline basaltic series or enriched light REE tholeiitic basalts
(Tournon, 1984 and 1994; Hauff et al., 2000) suggest that various basaltic units were possibly generated in other geodynamic settings such as seamounts or even rifts.