Wagon Bow pegmatites, Aquarius Mountains, Mohave County, Arizona, USAi

Regional Level Types
Wagon Bow pegmatites	Pegmatite Field
Aquarius Mountains	Mountain Range
Mohave County	County
Arizona	State
USA	Country

Wagon Bow Pegmatites

The Wagon Bow Pegmatites, three included this study, are located in the general area of 34° 91’4.92”N, 113° 52’3.85”W. The 3 pegmatites, herein referred to as Wagon Bow #1, #2 and #3 (Figure 8), are all located within a few kilometers of each other (Figure 9). Each pegmatite was sampled and analyzed but only #3 was mapped and extensively sampled. This is because Wagon Bows #1 and #2 are poorly exposed. Wagon Bow #1 has only a small quarry and #2 has only a prospect pits cut into the pegmatite.

The Wagon Bow #3 pegmatite, the smallest pegmatite in the study, intrudes into fine grained granite which is composed of quartz, biotite and feldspar up to 1.5 cm. Contacts with the wall zone are only exposed on the southwestern edge of the pegmatite and are sharply defined. No reaction boundaries with the host rock are evident.

This tabular pegmatite has an average thickness of 9 m and measured approximately 100 m in length. The pegmatite strikes 295° and dips 40-65° NE. This pegmatite has undergone extensive mining and removal of most of the core and wall zone leaving only approximately 10 m of pegmatite unexposed. At least four small, 15 m, unexplored and pegmatites are found in the nearby vicinity, all with roughly the same attitude. Accessory minerals collected from the mine dumps include xenotime, monazite with xenotime inclusions and ilmenorutile with cassiterite inclusions (Hanson et. al, 2005).

Like the Kingman Feldspar and Rare Metals pegmatites, the Wagon Bow pegmatites are F poor with white microcline, features that are atypical for NYF pegmatites.

Wall zone

The wall zone varies in thickness from 1-2 m and is composed of massive feldspars and minor amounts of REE-bearing minerals. Small pockets contained monazite crystals, some measuring up to 5-5.5 cm. These pockets on average contained 4-6 monazite crystals ranging in size from 3-5.5 cm. Accessory minerals include; epidote, hematite and goethite. Replacement units bearing HREE oxides are notably absent. While it is possible that they were completely removed during mining, this is unlikely as no HREE oxides were found in the dump material.

Core zone

The composite core of the pegmatite was 7-8 m thick and 60 m long, comprised of massive quartz and flesh-toned microcline with lesser amounts of muscovite near the margins.

Line Rock

Mining has exposed the line rock unit only along the southeastern end of the pegmatite where it is 1.4 m thick. This unit is comprised of grey muscovite, fine grained quartz and white albite. The fabric of this unit is distinct from the Rare Metals line rock as it exhibits a more linear layering which dips downward into the pegmatite (Figure 10).

The Wagon Bow pegmatites all intrude compositionally and texturally similar mildly peraluminous granite. This leucocratic granite is holocrystalline and exhibits a medium grained texture. It is hypidiomorphic with subhedral quartz, euhedral biotite, subhedral plagioclase and subhedral...(feldspar ?). The contacts with the wall zone are only seen on the southwestern end and, where exposed, show sharp definition and no significant reaction boundaries.

A much darker spotted granite was found only in one boulder at the Wagon Bow #1 pegmatite (Figure 12). The overall appearance of the granite is somewhat reddish in color with white spots that average 5 cm in diameter and encompass approximately 25% of the rock. The granite straddles the boundary between granodiorite and quartz monzanite (sic) (Figure 11). The spots are mineralogically identical to the remainder of the rock and are likely the result of a lack of oxidation in these areas. This mesocratic granite as a whole is also medium-grained in texture. It is holocrystalline and is comprised of euhedral biotite, anhedral quartz, subhedral plagioclase and subhedral feldspar. It differs from the other granites in the area as a large amount of euhedral muscovite is present, which contains 154 ppm of Tl (Table 53). This boulder was probably moved during the mining process, thus the possible relationship to the pegmatite is impossible to ascertain.