Archaean basic magmas
This chapter discusses Archaean basic magmatism, concentrating in particular on komatiite, komatiitic basalt and tholeiitic basalt suites. Archaean tholeiites are chemically distinct from their more modern counterparts and they are the most abundant magma type represented in greenstone belts, and thus they warrant significant attention. Several magma types are not discussed in this chapter since, although they were erupted during the Archaean, they are commonplace in more recent assemblages. These basalt types include those from typical continental bimodal suites (e.g. Bo wen et al, 1986), calc-alkaline (high-Al) basalts (e.g. Barley et al., 1984) and alkaline basalts (e.g. Cooke and Moorhouse, 1969). Also excluded from this account is a discussion of the parental magmas of Archaean gabbro-anorthosite complexes (Weaver et al, 1981; Windley et al, 1981), which are described in Chapter 4. Representative analyses of rocks discussed in this chapter are presented in Table 2.1.
KeywordsIncompatible Element Platinum Group Element Greenstone Belt Tholeiitic Basalt Komatiitic Basalt
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