Granite may have more alkali feldspar, whereas a granite derived from partial melting of metaigneous rocks may be richer in plagioclase. It is on this basis that the modern "alphabet" classification schemes are based. The letter-based Chappell & White classification system was proposed initially to divide granites into I-type (igneous source) granite and S-type (sedimentary sources). Both types are produced by partial melting of crustal rocks, either metaigneous rocks or metasedimentary rocks. M-type granite was later proposed to cover those granites that were clearly sourced from crystallized mafic magmas, generally sourced from the mantle. However, this proposal has been rejected by
Granite Wash Pass Granite Wash Pass Granite Wash Pass is a gap between the Granite Wash Mountains and the Little Harquahala Mountains, in La Paz County, Arizona. Granite Wash Pass is located at the southwest end of the Granite Wash Mountains and the northwest end of the Little Harquahala Mountains. The apex of the pass is at an elevation of 1,834 feet/559 meters. The Granite Wash Pass has been a route between the Colorado River and the interior of Arizona from November 1863 when teamsters Gird and Sage discovered a route what became the La Paz - Wikenburg Road through Granite Wash Pass.