The apparent lack of plate tectonics operating on the Moon (Taylor 1975) is also of importance in evaluating possible lunar material resources. Plate tectonics, which is characterized on Earth by a small number of large, broad crustal plates, each of which "floats" on a viscous underlayer (mantle) and moves more or less independently of the others, is fundamental to the development of most commercial type ore deposits and even petroleum deposits on Earth (Mitchell and Garson 1981, Hutchison 1983). One important aspect of plate tectonics on the Earth is the recycling and partial fusion of crustal materials to form granites and their related ore deposits and pegmatites (Mitchell and Garson 1981, Hutchison 1983). Even though a granite-like residual phase (mesostasis and "veinlets") and very small gr~nitic clasts in breccias occur in rocks on the Moon (Rutherford et al. 1976, Warren et al. 1983a), there is no evidence that large-scale granitic bodies occur on the Moon (Taylor 1975). Moreover, unlike the majority of similar Earth rocks, the granite-like Moon rocks are completely devoid of hydrous phases (Warren et al. 1983a).

Lunar Material Resources

The types of lunar materials available for exploitation (table ~1 can be grouped into four basic categories: whole rocks and minerals, regolith, fumarolic and vapor deposits, and nonlunar materials. We have very little direct knowledge of whole rocks in situ, and we know virtually nothing about possible fumarolic deposits. The Apollo and Luna missions were designed to study the lunar regolith, with cores taken a maximum of 3 meters deep (Carrier 1974, Taylor 1975). Thus, in the subsequent sections, I will mainly discuss the potential of the near-surface lunar regolith as a source of materials, especially as a source of volatile elements.

Rocks and Minerals

Rocks: The major rock types in, the maria are basalts, gabbros, pyroxene-rich peridotites, and breccias (Mason and Melson 1970, Levinson and Taylor 1971, Taylor 1975. Gillett 1983, Taylor 1984). The major rock types in the high1ands are various types of anorthosites; anorthositic gabbros;


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