The JTGM is essentially composed of harzburgite and dunite, but
lherzolite has also been reported from the lowermost part of the massif (Mahmood et al., 1995).
The residual character of the harzburgitic mantle xenoliths (believed tobe consistent with melting and basalt-component removal) is also indicated by the decrease in the cpx/opx modal ratio with decreasing modal cpx, which fits the model variation trend induced by partial melting of
lherzolite [56, 63].
Real in-situ measurement and rock sampling for laboratory measurement were carried out in the southern part of Balmuccia massif at a flat outcrop of the
lherzolite in the Sesia River Valley, between Balmuccia and Isola villages (Fig.
The relationship between these rocks and the adjacent units is tectonic, having been overthrusted on the Eocene flysch and Miocene marl and sandstone.Inside the serpentinites still traces of Pridotites of Harzburgite and sometimes
Lherzolite combination is observed in the form of floating pieces.
The Sabalan lavas are relatively similar to Salmas Quaternary basalts, characterized by low degree of partial melting (<0.1%) of a mantle source containing clinopyroxene-garnet
lherzolites (Figure 9).
The foliated peridotite is mainly harzburgite with minor dunite and
lherzolite. The dunite present is either interlayered with harzburgite or occurs as envelopes around harzburgite containing mostly podiform chromite deposits.
The second type recognized in the mafic-ultramafic bodies is dominated by variably metamorphosed ultramafic rocks (
lherzolite, harzburgite, wehrlite, dunite, and pyroxenite; Fig.
Xenoliths of eclogite and
lherzolite suggest a mantle origin; isotopic studies indicate an emplacement age around 35.6 to 70.5 million years.
This feature emphasizes their primitive source (garnet
lherzolite origin) and the absence of plagioclase in the early crystallization process.
Arc-related calc-alkalic and tholeiitic basalts typically show moderate degrees of light rare-earth-element (LREE) enrichment, and flat heavy rare-earth-element (HREE) profiles, indicating an origin in a shallow (spinel
lherzolite) mantle.
Although debated, primary magmas are thought to have Mg# values of about 0.72 as a result of equilibration with [Fo.sub.92] olivine that is found in most mantle
lherzolite xenoliths (Roeder and Emslie, 1970).