Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

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A whole-rock chemical analysis of one sample of quartz latite porphyry dike is given in table1. This sample has less than 1 percent xenocrysts, but it is not clear if this is due to less xenocrysts incorporated or more complete resorbtion of xenocrystic phenocrysts in this dike. The sample is chemically classified as a latiandesite and plots close to the boundary with dacite (De la Roche and others, 1980). A comparison of the composition of the quartz latite porphyry dikes with the average composition of two types of Mount Aetna ring dikes and the average composition of andesibasalt (table 2) indicates that the overall composition of the quartz latite porphyry is compatible with mixing of an intermediate composition magma with a Mount Aetna-related magma. Table 2. Whole-rock chemical comparison of quartz latite porphyry hybrid dike with Mount Aetna ring dikes and average andesibasalt. [Tmaqmp and Tmaqlp analyses by X- Ray Assay Laboratories, Don Mills, Ontario; Tqlp analysis by ALS-Chemex, Sparks, Nevada.] _________________________________________________________ Tmaqmp Tmaqlp Tqlp Dike Andesibasalt SiO 2 67.7 67.5 58.53 53.44 Al 2 O 3 14.8 15.0 16.23 16.93 Fe 2 O 3 3.25 1 3.30 1 7.49 1 3.75 FeO - - - 5.58 CaO 2.17 2.50 4.57 8.36 MgO 1.07 1.00 3.33 4.76 Na 2 O 3.91 3.69 3.60 3.04 K 2 O 4.64 4.51 3.26 1.24 TiO 2 0.45 0.46 1.14 1.19 MnO 0.06 0.06 0.07 0.15 P 2 O 5 0.20 0.20 0.53 0.23 H 2 O + 1.08 1.16 0.88 2 0.86 H2O - - - - 0.52 TOTAL 99.3 99.38 99.63 100.05 _________________________________________________________ Tmaqmp 84-81-3 Mount Aetna Type 2 quartz monzonite porphyry ring dike (Shannon, 1988) Tmaqlp 85-42c Mount Aetna Type 3 quartz latite porphyry ring dike (Shannon, 1988) Tqlp Dike 05-258 Tertiary quartz latite porphyry hybrid dike Andesibasalt - Average andesibasalt- CLAIR database, 918 analyses (De la Roche and others, 1980) 1 2 Total Fe as Fe 2 O 3 Reported as LOI- Loss On Ignition (volatiles) 88
The age of the quartz latite porphyry dikes is uncertain. The dikes cut the Proterozoic rocks (Xgdf, Xag, Xhig, and Xgp) on the southeast slopes of Mount Shavano. In the Maysville quadrangle, projected float trends of quartz latite porphyry hybrid and rhyolite porphyry (Trp) dikes intersect, but cross-cutting age relationships could not be established. Similar dikes, but with less evidence of xenocrysts, cross cut the Mount Princeton pluton in the Garfield quadrangle and cross cut the Mount Princeton pluton and Mount Aetna quartz monzonite ring dike in the Mount Antero quadrangle. Thus, field relations of the quartz latite porphyry hybrid dikes in the Maysville, Garfield, and Mount Antero quadrangles suggest a dike event that is younger than the Mount Princeton pluton and the Mount Aetna quartz monzonite porphyry ring dikes. The field relations, petrographic and chemical character of the quartz latite porphyry hybrid dikes suggest they represent a late-Mount Aetna magmatic event where an intermediate composition, andesitic magma locally mixed with phenocryst-bearing Mount Aetna magma. Mount Aetna cauldron (~34.4 Ma) – The Mount Aetna cauldron represents a major magmatic event in the southern Sawatch Range. It is a highly eroded volcano-plutonic subsidence structure that represents the roots of a mid-Tertiary ash-flow caldera related to the middle Tertiary magmatic pulse. The Maysville quadrangle is situated almost entirely outside the southeastern margin of the Mount Aetna cauldron ring zone (fig. 4). The outermost ring zone cuts across the very northwestern corner of the Maysville quadrangle, about 2,500 ft northwest of the summit of Mount Shavano (plate 1). About 1,300 ft of the about 2,000 ft total width of the ring zone is in the Maysville quadrangle. The ring zone is very poorly exposed on the steep southeast talus slope of Tabeguache Peak in the Maysville quadrangle. On the basis of float mapping, the Mount Aetna ring zone here includes a Mount Aetna quartz monzonite ring dike (Tma), flinty crush rock (Tfcr), and brittle-ductile ring shears (Trs). The southeastern ring zone predominantly dips steeply (70° to 80°) inward to the northwest, but some ring shears dip steeply outward to the southeast (Shannon, 1988). The southeastern Mount Aetna cauldron ring zone is truncated by the younger Mount Antero leucogranites about 4,500 ft 89
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OPEN-FILE REPORT 06-10 Geologic Map
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TABLE OF CONTENTS Introduction…
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mylonitic, augen textures………
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INTRODUCTION LOCATION AND ACCESS Th
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SAWATCH RANGE RIFT-SHOULDER UPLIFT
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of the South Arkansas River (subseq
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EXPLANATION Rio Grande Rift Neogene
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in descriptions of the geologic uni
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During the Early and Middle Paleozo
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Mountains, and White River uplifts
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field are the largest remnants of t
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Figure 5. Detailed geologic-structu
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with the Colorado mineral belt (Boo
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Shannon, 2005). Widmann and others
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the Upper Arkansas graben (fig. 5)
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15-minute quadrangle, which is adja
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etween the northern and southern se
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on U.S. Forest Service color aerial
Page 37 and 38: We use fractional map units on the
Page 39 and 40: Qpt Pinedale till, undivided (late
Page 41 and 42: weathered, but Mount Princeton quar
Page 43 and 44: stratified, matrix-supported, bould
Page 45 and 46: as rockfalls, rock avalanches, rock
Page 47 and 48: stream-channel deposits of all pere
Page 49 and 50: Figure 10. View west up South Arkan
Page 51 and 52: Figure 11. View west up South Arkan
Page 53 and 54: valley near the eastern map boundar
Page 55 and 56: lithologies are variable and depend
Page 57 and 58: Arkansas River in parts of Redman C
Page 59 and 60: angular to subangular. Deposits gen
Page 61 and 62: elations, age constraints from foss
Page 63 and 64: elated to the inferred Squaw Creek
Page 65 and 66: Figure 14. Crude bedding in coarse
Page 67 and 68: microcline, and muscovite. The latt
Page 69 and 70: Volcanic Ash Figure 17. View of eas
Page 71 and 72: Figure 18. Close-up view of intense
Page 73 and 74: The western zone of brecciated Pale
Page 75 and 76: Tr Rhyolite dikes (early to late Ol
Page 77 and 78: as the overall N47°E trend of the
Page 79 and 80: One age determination on the rhyoli
Page 81 and 82: northwest-trending fault. Thus, fie
Page 83 and 84: on the North Fork leucogranite intr
Page 85 and 86: A small 400 by 400 foot body of Nor
Page 87: N12°E, 62°NW (about 6,000 ft sout
Page 91 and 92: Tma Mount Aetna quartz monzonite po
Page 93 and 94: of the Maysville quadrangle and the
Page 95 and 96: Mount Aetna ring dikes (Tma), one i
Page 97 and 98: the margins of the pluton, includin
Page 99 and 100: Shannon (1988). The average of seve
Page 101 and 102: indicating a granite b composition
Page 103 and 104: analysis by Crawford (1913), two an
Page 105 and 106: locally tanish to pinkish gray. It
Page 107 and 108: quadrangle (tables 1 and 3) were fr
Page 109 and 110: slices of Paleozoic sedimentary roc
Page 111 and 112: south-southwest of Maysville is a 9
Page 113 and 114: There is one additional Paleozoic s
Page 115 and 116: near the southwest margin of the qu
Page 117 and 118: eastern contact of the diorite intr
Page 119 and 120: endoskarn zones. The two widely sep
Page 121 and 122: Xhig) along the southeastern contac
Page 123 and 124: Xgd Granodiorite (Early Proterozoic
Page 125 and 126: Hybrid granodiorite is locally deve
Page 127 and 128: Xcs Calc-silicate gneiss (Early Pro
Page 129 and 130: Many of the calc-silicate gneiss zo
Page 131 and 132: typically expressed by intermittent
Page 133 and 134: The field relations and characteris
Page 135 and 136: the north side of all three segment
Page 137 and 138: eplaced by muscovite. The western m
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sillimanite-quartz-muscovite that a
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sillimanite gneiss (Xmsg) and the m
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Figure 35. Outcrop of Proterozoic h
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samples) indicates they are compose
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Xal Lineated amphibolite (Early Pro
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of the Proterozoic metamorphic rock
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that the present structural configu
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elated to rotation of domain blocks
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sometimes terminate at a cross stru
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limestone that is exposed in a wind
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quadrangle are intimately associate
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of the quadrangle. The north-northw
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quartz monzonite ring dikes (Tma).
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that truncates the Upper Arkansas g
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as at the mouth of Squaw Creek. How
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adjacent to the southwestern edge o
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graben and the Upper Arkansas Valle
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GEOLOGIC HAZARDS Potential geologic
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In addition, older landslides may h
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sparse vegetation. One such area is
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Table 7. Historical (pre-instrument
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4262272N. ECONOMIC GEOLOGY Currentl
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A number of the larger pegmatite bo
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River placers near Buena Vista (Van
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The small mines and prospects along
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elatively recent (post-1970) explor
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contact of two Quaternary gravels (
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quadrangle. The first area is a clu
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y Sharp (1976) to be a fault slice
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quadrant of the Maysville quadrangl
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the large Paleozoic rock outlier) i
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WATER RESOURCES Water resources on
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water near Maysville is being produ
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to Rudy C. Epis: Colorado School of
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University, M.Sc. thesis, 50 p. Din
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Hutchinson, R.M., and Hedge, C.E.,
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Litsey, L.R., 1958, Stratigraphy an
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County, Colorado, in Berg, R.R., an
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Stark, J.T., and Barnes, F.F., 1935
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Tweto, O., 1987, Rock units of the
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quadrangle, Colorado: U.S. Geologic
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94A 391996 4263422 Prospect YXp;Xbf
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336A 396189 4274961 Prospect Xgdf B
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854 391849 4268852 42 Adit; Geochem
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Geologic Map of the Maysville Quadrangle, Chaffee County, Colorado

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