petrology of ultramafic and related rocks along iraqi zagros thrust zone

(+Cr)]VI by [M 2+ Si 4+ ]VI, where M = Mg and Fe, occurs in majoritic garnet
and [Mg 2+ Na 1+ Al 3+ ]VI-VIII by [1.5Si 4+ ] occur in supersilicic clinopyroxene.
The effect of pressure drops on the genesis of exsolution lamellae, and
significance of their occurrences need to be systematically investigated.
Detailed characterization and experimental investigations regarding
exsolution microstructures of these minerals in UHP rocks will improve
our understanding of mantle processes and continental subduction.
1-2 Associated rocks with serpentinized ultramafic rocks
Rocks intimately associated with serpentinitized ultramafic rocks or
found as inclusion in serpentinite are of quite different types and sizes,
but are recognized as an integrated product of the serpentinization
process; they are rodingite, jadeitite and albitite (e.g., Coleman, 1980,
Harlow, 1994; Dubińska et al., 2004; Mohammad et al., 2007).
1-2-1 Rodingite
Rodingite is a Ca-rich, and SiO 2 -undersaturated rock, consisting of
Ca-Al and Ca-Mg silicates. It was formed by metasomatism of varied rock
types during serpentinization of host peridotite (e.g., Coleman, 1977;
Laech and Rodgers, 1978; Evans et al., 1979; Schandl et al., 1989;
ƠHanley et al., 1992; Mohammad et al., 2007). The protolith of rodingite
ranges from gabbro to quartzite (ƠHanley, 1996). Rodingite has been
reported from several ophiolite complexs (e.g., Carpedri et al., 1978;
Dubińska et al., 2004; Hatzipanagiotou and Tsikouras, 2001, Mohammad,
2004), as well as from Archean mafic sequences and present day ocean
floors (Honnorez and Kirst, 1975; Anhaeusser, 1979; Schandle et at.,
1989). In general rodingite is enveloped by chlorite shell labeled as
blackwall (e.g., Forst, 1975; Laech and Rodgers, 1978; Evans et al., 1979;
ƠHanley et al., 1992; ƠHanley, 1996; Mohammad et al., 2007).
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