Field_ID Latitude Longitude Rock_Type Rock_Description Alt_Minerals Alt_Style MO15_001 37.4648 -90.5169 Lake Killarney Formation "Float of maroon-colored, 15-20 percent alkali feldspar and 1 percent quartz, crystal-rich rhyolitic tuff. Contains stringers of flattened pumice." Clay (kaolinite?) "Weak deuteric, slight bleaching and weathering" MO15_002 37.4573 -90.501 Tuff at Little Rock Creek "Maroon-colored, crystal-lithic tuff with alkali (pink) feldspar greater than quartz phenocrysts. 10 percent phenocrysts and 10 percent lithics. Lithic clasts are dark gray, angular, and up to 1-2 cm diameter. Lithic clasts andesite to basaltic andesite?." None observed None MO15_003 37.4489 -90.5419 Basaltic andesite of Marble Creek campground "Fresh, dark gray, basalitc andesite. Very fresh. Sample collected for analysis of melt inclusions in zircon. Contains large, angular rhyolitic lithic clasts." None observed None MO15_004 37.5482 -90.5223 Lake Killarney Formation "Grayish-maroon, aphanitic groundmass with 10 percent phenocrysts (quartz>>alkali feldspar), with flattened pumice and lithophysae." None observed None MO15_005 37.5115 -90.6102 Grassy Mountain Ignimbrite Crystal-lithic tuff with course grained (1-2 mm diameter) phenocrysts of quartz and alkali feldspar (1-3 mm) set in a dark gray alkali feldspar phyric angular autholithic tuff None observed None MO15_006 37.5724 -90.6951 Royal Gorge Rhyolite Rhyolite "Hematite, quartz, alkali feldspar, sericite" Deuteric MO15_007 37.6167 -90.6556 Shepherd Mountain Rhyolite Site=MO13_003. Sampled for age date. Very weakly altered here "Hematite, alkali feldspar" Disseminated MO15_008 37.6112 -90.6311 Shepherd Mountain Rhyolite "Dark maroon-colored rhyolitic tuff with aphanitic groundmass with streaks of flattened (1:100 ratio) lithophysae that are 3-mm thick and lined with quartz+alkali feldspar+hematite. Possible devitrification features with late vapor phase gas alteration and unflattened pumice. Strike=130, dip=25 SW" "Hematite, alkali feldspar" Disseminated MO15_009 37.6144 -90.6062 Pilot Knob Felsite/Irontown Hollow Rhyolite "Light pink, crystsal-poor, aphanitic rhyolite with lighter and darker bands and autoliths. Lithic fragments are plastically deformed suggesting autoclastic origin as the flow cooled and brecciated during flow. Flow-banded rhyolite associated with a flow-dome complex? Late vugs filled with quartz+hematite+fluorite looks to be IOCG-type alteration. IOCG-type alteration weak to moderate, with epidote+fluorite+hematite+quartz" "Hematite, fluorite, epidote, quartz" Vug infilling MO15_010 37.6573 -90.6831 Graniteville Granite "Sample from quarry dump, near fence " None observed None MO16_001 37.4416 -90.5575 Rhyolite of Marble Creek/Lower Campground Chocolate-colored aphanitic matrix with 5-7 percent salmon-colored alkali feldspar phenocrysts. No quartz seen. Fluorite in vug. Sampled for high resolution U-Pb zircon geochronology. Outcrop along Marble Creek east and downstream of dam. Fluorite Weak MO16_002 37.5956 -90.5589 "Brown Mountain unit (Sides, 1983)" "Subvolcanic unit similar to the Silvermine Granite ring intrusion. Dark pink, holocrystalline subvolcanic texture with dark green anhedral ovoid-shaped mafic mineral (clinopyroxene?)" None observed None MO16_003 37.5953 -90.5589 "Brown Mountain unit (Sides, 1983)" "Dark pink, holocrystalline subvolcanic texture with dark green anhedral ovoid-shaped mafic mineral (clinopyroxene?)." Disseminated magnetite Disseminated MO16_004 37.4353 -90.6008 "Lower Ridge tuff (Brown, 1988)" Crystal-rich lithic-bearing ash flow tuff with 15 percent phenocrysts of broken feldspar (plagioclase?) and silicified flattend pumice/fiamme set in a maroon-colored matrix. "Hematite, quartz" Disseminated MO16_005 37.425 -90.6092 "Upper Ridge tuff (Brown, 1988)" "Lithic-rich rhyolitic ash flow tuff with maroon-colored fine-grained tuff matrix with flattened pumice/fiamme. Lithic fragments are dark gray (andesite?), angular, up to 5 cm in diameter " "Hematite, quartz" Disseminated/incipient MO16_006 37.4239 -90.581 "Ridgetop volcanic rocks (Brown, 1998)" Heterolithic tuff breccia with angular to subangular cobble- to pebble-sized clasts of rhyolitic tuff set in dark red rhyolitic matrix. 15 percent phenocrysts (plagioclase>quartz) Hematite Weak MO16_007 37.4243 -90.5732 "Upper Ridge tuff (Brown, 1988)" "Maroon-colored lithic-rich tuff with cobble- to pebble-sized angular fragments and flattened pumice in martix. Alteration ~1 percent hematite disseminated in matrix, reddening as well. Pumice with quartz+hematite. " "Hematite, quartz" Weak MO16_008 37.4276 -90.5694 "Lower Ridge tuff (Brown, 1988)" Dark maroon-colored crystal-rich tuff with 15-20 percent plagioclase phenocryts set in a fine-grained matrix. Late fluorite alteration in lithophysae Fluorite Disseminated and in lithophysae MO16_009 37.4317 -90.5555 "Upper andesite (Brown, 1988)" Basaltic andesite with 10 percent green glassy mafic (olivine?) with radiating clusters of plagioclase phenocrysts set in dark gray matrix. Alteration of late calcite+epidote "Epidote, calcite, hematite" Disseminated and in lithophysae MO16_010 37.4409 -90.5472 "Upper andesite (Brown, 1988)" Basaltic andesite flow. Vesiculated flow top with calcite crystallized in lithophysal cavities. "Epidote, calcite, hematite" Disseminated and in lithophysae MO16_011 37.4228 -90.545 "Upper Ridge tuff (Brown, 1988)" Maroon-colored lithic-rich tuff with angular rhyolite clasts. Alteration of disseminated hematite with reddening of matrix near hematite (alkali feldspar?). "Hematite, reddening" Disseminated MO16_012 37.428 -90.5178 "Upper andesite (Brown, 1988)" "Very distinctive unit. Approximately 5 percent plagioclase laths set in dark gray aphanitic matrix. Unusual calcite+quartz+epidote+chlorite infilling of amygdules, with minimal secondary alteration minerals." "Epidote, chlorite, calcite, quartz" Amygdule infillings MO16_013 37.431 -90.5142 "Lower andesite (Brown, 1988)" "Dark gray to black, aphanitic amgydaloidal basalt to basaltic andesite. Amygdules filled with epidote+chlorite+calcite+quartz" "Epidote, chlorite, calcite, quartz" Amygdule infillings MO16_014 37.4318 -90.5092 "Lower andesite (Brown, 1988)" Aphanitic basalt with late epidote alteration "Epidote, chlorite, calcite, quartz" Amygdule infillings MO16_015 37.4133 -90.5829 "Tile red tuff (Brown, 1988)" """Red tile"" colored, aphanitic matrix with 5-7 percent broken phenocrysts of plagioclase and lesser smokey quartz. Has distintive concoidal fracturing. No alteration seen." None observed None MO16_016 37.4687 -90.6175 "Lower andesite (Brown, 1988)" Basaltic andesite with distinctive epidote-coated fractures. 5 percent plagioclase phenocrysts. Outcrop about 0.85 km south of Crane Mtn lookout outcrop. "Epidote, calcite, quartz" Fractures and disseminated MO16_017 37.4765 -90.6216 Rhyolite clasts in trachyandesite of South Crane Mountain Rhyolite clast in trachyandesite flow. Sampled for dating. Titanite fills late vug. Light pinkish-gray clasts set in dark gray to black fine-grained trachyandesite matrix with 15 to 20% large phenocrysts of feldspar. Epidote alteration in pods and cavities "Epidote, calcite, quartz" Pods and cavity infilling MO16_018 37.6294 -90.6441 Rhyolitic breccia; Cedar Hill area Polylithic volcanic breccia with clasts of various rhyolite tuffs. Some fragments are flattened; may mean have been hot at the time of deposition. Rock was an agglomerate or a lithic-rich ash flow tuff. Matrix looks to be silicified. Alteration=silica+ hematite (specularite in intersticies. IOCG = 2-3 weak/moderate. "Hematite, quartz" Disseminated MO16_018A 37.6298 -90.6442 Flow-banded rhyolitic tuff; Cedar Hill area "Pink flow-banded rhyolite overlain by 1 m thick homogeneous rhyolite tuff. Flow banding in rhyoolite Strike=260, dip=46." "Hematite, quartz" Disseminated MO16_019 37.6301 -90.6439 Massive ryholite tuff horizon; Cedar Hill area Pale red massive rhyolite tuff "Hematite, quartz" Disseminated MO16_020 37.6306 -90.6439 Flow-banded rhyolitic tuff; Cedar Hill area "Flow banded, dark red/maroon-colored rhyolite. Spherulitic texture. IOCG alteration code=2, disseminated hematite and clay" "Hematite, quartz, clay" Disseminated MO16_021 37.6322 -90.6448 Hydrothermal breccia; Cedar Hill area Hydrothermal breccia at the top of the hill "Hematite, quartz" Fracture and matrix filling MO16_022 37.6314 -90.6458 Cedar Hill hematite ore Breccia zone with ore. Hematite and jasper ore within brecciated rock. "Hematite, jasper" Fracture and matrix filling MO16_022A 37.6323 -90.6459 Cedar Hill hematite ore Trenched mine workings strike northwest at 305-310. "Hematite, jasper" Fracture and matrix filling MO16_023 37.6329 -90.6468 Matrix-supported polylithic volcanic breccia; NW side of Cedar Hill Volcanic breccia. Heterolithic breccia with clasts of light and dark rhyolite. Matrix-supported polylithic breccia with clasts of banded tuffs and fine-grained dark gray volcanic and dark marroon rhyolite. Matrix looks silicified. More heterolithic than the polylithic tuff at MO16-18. IOCG type alteration is weak; hematite Hematite Disseminated MO16_023B 37.6329 -90.6407 Matrix-supported polylithic volcanic breccia; NW side of Cedar Hill "Composite sample for geophysical study of potassium metasomtism. IOCG-hematite, weak, veins." Hematite Veins MO16_023C 37.6334 -90.6470 Matrix-supported polylithic volcanic breccia; NW side of Cedar Hill Matrix supported polylithic breccia-same as MO16_023. Hematite Veins MO16_024 37.5853 -90.5826 Grassy Mountain Ignimbrite Rhyolite along MO hwy 72 at Stouts Shut-in. Sampled for precise U-Pb zircon age Hematite Disseminated MO16_025 37.5925 -90.5740 Lake Killarney Formation Crystal poor tuff. Sampled for high resolution U-Pb zircon geochronology. Freshest zone within road cut. Hematite Vein and disseminated MO16_026 37.5591 -90.5488 Granite of Brown Mountain Brown Mountain ring intrusion. Pink fine- to medium-graned hypabyssal intrusion. Dark mafic clots. Minor biotite with anhedral alkali feldspar. Trace quartz. Fe-oxide disseminated throughout. Hematite Disseminated MO16_027 37.1721 -91.2441 Lower unit of Coot Mountain Grayish pink rhyolite ash flow tuff; groundmass has graphic intergrowth of quartz and feldspar. MO16_028 37.1662 -91.2504 Upper unit of Coot Mountain Grayish red rhyolite ash flow tuff. MO16_029 37.1688 -91.2514 Lower unit of Coot Mountain "Grayish red rhyolite ash flow tuff; groundmass: weakly devitrified ash(?); intergrowth of quartz, feldspar, and opaque oxide minerals. Densely welded ash-flow tuff. Abundant secondary SiO2 filling elongate lithophysae." MO16_030 37.1723 -91.2514 Upper unit of Coot Mountain "Grayish red rhyolite ash flow tuffs: groundmass is devitrified/recrystallized ash(?); intergrowth of quartz, feldspar, and opaque oxide minerals. Densely welded ash-flow tuff. Secondary SiO2 in veinlets and filling elongate interlayers; some secondary epidote." MO16_031 37.1676 -91.2508 "Volcaniclastic conglomerate, breccia, sandstone" "Grayish orange volcaniclastic sandstone related to rhyolite ash flow tuffs; volcanic sandstone is matrix supported, and poorly sorted; contains subangular quartz and alkali feldspar clasts. Clasts are 0.2 to 1 (0.5) mm. Clasts include granophyric tuff and minor pumice fragments." MO16_050 37.6131 -90.6414 Shepherd Mountain Rhyolite Collected from boulders at foot of mountain for geophysical evaluation of potasium metasomatism Hematite Facture surfaces MO16_051 37.6132 -90.6427 Shepherd Mountain Rhyolite "Dark purple rhyolite with flattened pumice, 10-15 percent alkali feldspar phenocrysts set in a matrix containing disseminated 1-2 percent opaque oxide minerals. Fracture surfaces are coated with Fe-oxide and silica. Outcrop is 4 m north of path in natural boulder field. " "Hematite, quartz" Facture surfaces and disseminated in matrix MO16_052 37.6131 -90.6438 Shepherd Mountain Rhyolite Rhyolite subcrop collected for geophysical physical properties measuresments. MO16_053A 37.6124 -90.6459 Shepherd Mountain Rhyolite Rhyolite collected for geophysical physical properties measuresments. MO16_053A 37.6124 -90.6462 Shepherd Mountain Rhyolite Rhyolite tuff MO16_054 37.6114 -90.6461 Shepherd Mountain Rhyolite Rhyolite collected for geophysical physical properties measuresments. MO16_055 37.6111 -90.6464 Shepherd Mountain Rhyolite Top of mine dump. Mine workings trend N55E. Geophysical measurements made on the soils on atop the dump. MO16_056 37.6113 -90.6461 Shepherd Mountain Rhyolite Middle of the annular potassium geophysical anomaly. NE tip of south trench. Dark purple altered rhyolite with alkali feldspar and quartz phenocrysts. Allteration is strong. Mineralogy= hematite + jasper replacing pumice fragments. Sampled for alteration extent determination approximately 10 m south of pit. "Hematite, jasper" MO16_057 37.6059 -90.6466 Shepherd Mountain Rhyolite Rhyolite tuff Disseminated MO16_058 37.6114 -90.6408 Shepherd Mountain Rhyolite Dark marron colored. Alkali feldspar phyric rhyolite with flattened pumice. Matrix is altered with Fe-oxide+japser+alkali feldspar "Hematite, jasper, alkali feldspar" Disseminated MO16_059 37.6992 -90.6395 Iron Mountain felsite Taum Sauk caldera sequence. Dark gray plagioclase-phyric rhyolite with distinct flattened pumice with moderate to strong amount of epidote veining and dissemination; highly magnetic Epidote Veining and in groundmass MO16_061 37.6814 -90.5991 Tribby Breccia Lithic tuff with light greenish gray fine-grained lithic fragments set in dark purplish gray matrix white feldspar and fine grained white lithic franments of quartz-phyreic rhyolite; weathers light pink; lithic tuff or tuff breccia? Alteration: epidote replacing clasts and disseminated in matrix Epidote Veining and in groundmass MO16_062 37.6784 -90.6006 Tribby Breccia Polylithic tuff breccia. Weak epidote alteration. Lacks epitdote veining like other nearby outcrops Epidote Disseminated MO17_001 37.84355 -90.27299 Silver Mines basaltic andesite "Dark gray, intermediate composition dike with distinctive 1-2 cm alkali feldspar and 2-4 mm quartz phenocrysts, has been correlated with Silver Mines basaltic andesite" "Pyrite, chlorite, epidote" None MO17_002 37.84185 -90.26603 Breadtray Granite Medium grained biotite granite with major quartz and alkali feldspar and minor plagioclase; exposed along south fork of Jonca Creek Chlorite None MO17_003 37.58999 -90.36959 Skrainka Diabase "Very fresh, dark gray, equigranular Skrainka diabase. Contains about 50 percent plagioclase, greater than 20 percent clinopyroxene and olivine, and about 3 percent biotite" Chlorite None MO17_004 37.55830 -90.44192 Silver Mines basaltic andesite "Dark gray, aphanitic Silver Mines basaltic andesite dike with abundant plagioclase microlites" Clay None MO17_005 37.53944 -90.83775 Cope Hollow Formation-basalt "Dark gray, aphanitic Cope Hollow basalt flow interlayered with Cope Hollow rhyolite ash-flow tuffs. Contains abundant plagioclase microlites" Clay None MO17_006 37.56880 -90.14969 Amidon syenogranite Castor River Shut-ins inequigranular hypersolvus granite. Contains abundant quartz and perthitic alkali feldspar and minor hornblende None observed None