Ongonite and topazite dikes in the Flying W ranch area, Tonto basin, Arizona

The petrogenesis of the topaz-rich ongonite and topazite dikes in the Flying W ranch area (Tonto basin, Arizona) was investigated, and the possible origin of the topaz in the Flying W rhyolite is discussed. The field, textural geochemical, and mineralogical characteristics of the topaz-bearing dikes in the Flying W ranch area all were found to support the genesis of the topaz-bearing bodies from a magma. The evidence obtained contradicts an origin for these rock types by greisenization or veining.