Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

mylonitic, augen textures……………………………………………. 121
Figure 28. Subcropping contact between Proterozoic granodiorite (Xgd,
boulder upper left) and amphibolite gneiss (Xag; dark gray
clasts)…….......................................................................................... 124
Figure 29. Outcrop of epidote calc-silicates overprinting the matrix
of Proterozoic amphibolite agglomerate (Xaa)…………………….. 128
Figure 30. Outcrop of Proterozoic quartzite (Xq) representing lenses of
metachert ()……………………………………………………….. 132
Figure 31. Subcropping zone of muscovite-cordierite schist (Xmc) with
large porphyroblasts of cordierite (dark brown)…………………… 134
Figure 32. Photomicrograph of muscovite-cordierite schist (Xmc) showing
cluster of cordierite porphyroblasts………………………………… 135
Figure 33. Hand sample, billet and slab of muscovite-sillimanite gneiss
(Xmsg)……………………………………………………………… 137
Figure 34. Hands samples of Proterozoic muscovite felsic schist (Xmfs)
showing medium- to coarse-grained, quartz-rich variety (left)
and fine- to medium-grained muscovite porphyroblastic variety
(right)…….......................................................................................... 140
Figure 35. Outcrop of Proterozoic hornblende intermediate gneiss (Xhig)
with localized mylonitic fabrics…………………………………… 143
Figure 36. Outcrop of Proterozoic amphibolite agglomerate (Xaa) with mixed
mafic and felsic metavolcanic clasts……………………………….. 146
Figure 37. Outcrop of Proterozoic lineated amphibolite (Xal)………………... 148
Figure 38. Steep rift-related fault cutting California leucogranite (Tcm)
in upper Squaw Creek……………………………………………... 162
Figure 39. Summary of Rio Grande rift architecture and location of
Tertiary and Quaternary volcanic ash localities…………………... 170
Figure 40. Photomicrograph of mineralized calc-silicate gneiss (Xcs) from
the Bon Ton mine- SW adit……………………………………….. 194
LIST OF TABLES
Table 1. Whole-rock chemical analyses of select igneous rocks from the
Maysville quadrangle, Colorado…………………………………….. 78
Table 2. Whole-rock chemical comparison of quartz latite porphyry hybrid
dike with Mount Aetna ring dikes and average andesibasalt………... 88
Table 3. Whole-rock chemical comparison of Tertiary () andesite hybrid
dikes with average rhyolite and andesibasalt………………………... 107
Table 4. Compilation of Miocene-Pliocene and Quaternary volcanic ash
localities in the southern part of the Upper Arkansas Valley graben
and South Arkansas graben…………………………………………. 172
Table 5. Summary of landslide deposit areas, by map unit in the Maysville
quadrangle…………………………………………………………… 173
Table 6. Summary of measured earthquakes within a 6-mi radius of the
center of the Maysville quadrangle…………………………………. 177
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