Soil genesis involving felsic rocks frequently involves understanding the r
oles of climate and time on the transformations of the primary minerals int
o secondary products. This study focuses on the weathering of peralkaline f
elsics in a semiarid climate. Soils and fresh parent materials were collect
ed from different microclimate regimes in the Chisos Mountains of Big Bend
National Park, Texas. Soils in the Chisos mountains generally have either a
mollic-argillic-rock or a mollic-rock horizon sequence, whereas other site
s at lower and drier locations have an ochric-rock horizon sequence. Atmosp
heric deposition of Ca and Sr and wind deflation of clay are important attr
ibutes of soil genesis. Elemental loss rates of Si, Al, K, Na, and other el
ements are appreciable, suggesting that leaching has been important to the
soil formation. Iron oxide formation, which is related to the moisture regi
me, is greater in soils having wetter microclimates. Solution chemistry sug
gests that Mg concentrations are appropriate for smectite synthesis and mai
ntenance, potassium concentrations reflect the presence of feldspar, sodium
concentrations reflect their loss rates because of leaching, and calcium r
eflects the presence of calcite. The rare earth elements similarly demonstr
ate loss rates consistent with chemical weathering. In general, chemical we
athering of feldspars, atmospheric deposition of Ca and Sr, and wind deflat
ion are important pedogenic processes.