USGS Professional Paper 1361 - State of Arizona Department of ...

6 GEOLOGY AND GOLD MINERALIZATION OF THE GOLD BASIN-LOST BASIN MINING DISTRICTS, ARIZONAUnconformityUnconformity8UnconformityCORRELATION OF MAP UNITSDESCRIPTION OF MAP UNITS~ Sedimentary deposits (Quaternary)-Includes sand and gravel alongactive stream washes. talus. colluvium. poorly consolidatedfanglomerate currently being dissected, and landslide deposits;also may include extensive high-level fanglomeratic deposits. westof Grand Wash Cliffs in general area of Grapevine Mesa, that maybe Tertiary and (or) Quaternary in ageIOTgIFanglomerate (Qullternary and (or) Tertiary)-Locally derivedfanglomerate deposits that include mostly clasts of metamorphicrock south-southeast of Senator Mountain and that do notcontain clasts of rapakivi granite or any interbedded tuffsMuddy Creek Formation (Tertiary)ITml I Hualapai Limestone Member-Includes limestone interbedded withthin beds of limy claystone, mudstone, and siltstone. Weatheredlimestone beds have a predominantly reddish color and form steepcliffs where they are dissected by Hualapai WashITmblIOTglUnconformityTmlTmbTmfUnconformityUnconformityI YdblUnconformity1".1"'I} I xgclIXbm11 x1ml~} I XfgI Xmg Xm0 IxmllIxgnl} Quaternary}Quaternary and(or) TertiaryTertiary} CretaceousCENOZOIC} MESOZOIC} PALEOZOICEARLYPROTEROZOICBasalt- As shown, flows at Senator Mountain. near west edgeof map area. and at Iron Spring Basin, near east edge. Basalt inthese two areas correlates probably with basalt Dows (not shown)that conformably underlie the Hualapai Limestone Member andalso are interbedded with fanglomerate 01 the Muddy Creek Formationnear northwest corner of map area. Whole-rock K-Ar agedetermination of basalt from this area yields age of 10.9 Ma (seesection by E.H. McKee, this report)}MIDDLEPROTEROZOICFanglomerate-Alluvial fanglomeratic deposits that include conglomerate.sandstone. siltstone. mudstone. and locally abundantgypsum lenses. Locally includes lenses and beds of rhyolitic tuffand, as shown near southwest corner of map area. fanglomeratemapped previously by Blacet (1975) as unit n. Unit is also intrudedby minor basalt dikes, especially in general area of Senator Mountain.Near northwest corner of map area. unit includes wellexposedDows of basaltG Volcanic rocks (Tertiary)-Includes mostly andesite. Map unit nearnorthwest corner of map area internally is highly broken bynumerous faults, and near here, unit also includes air-fall tuff andreddish·brown sandstone interbedded with chaotic sedimentarybreccia composed of fragments of Early Proterozoic gneiss. Inplaces, unit also includes massive porphyritic hornblende andesiteand basalt Dows and breccia and overall minor amounts of tightlycemented volcaniclastic rocks. Flow layering and bedding gener·ally dip at angles of 35' in contrast with shallow dips of about 5'in unconformably overlying basal fanglomerate of the MuddyCreek Formation. Age ranges of 11.8 to 14.6 Ma are reported neartype section of the Mount Davis Volcanics (Anderson and others,1972), whereas K·Ar age determination on sanidlne from air-Ialltuff near Salt Creek Wash in northwestern part of area yields ageof 15.4 Ma. The volcanic rocks may be equivalent of the MountDavis Volcanics or the Patsy Mine Volcanics (see section by E.H.McKee, this report).G Rhyolitic tuffaceous sedimentary rocks and fanglomerate (Tertiary)­Includes well·bedded mudDows and rhyolitic tuffaceous sedlmen·tary rocks and minor amounts of fanglomerate. Crops out as steeplydipping sequence of rocks, bounded by north-striking faults, nearsouth end of Lost Basin Range. Possibly equivalent to the MountDavis VolcanicsG Fanglomerate (Tertiary)-Coarse fanglomeratic deposits that locallyinclude landslide or mudDow breccia. Overlain unconlormably byfanglomeratic deposits of the Muddy Creek Formation, and apparentlyIntercalated with andesite possibly equivalent to theMount Davis VolcanicsI Tmf IFIGURE 2.-Continued.Two·mica monzogranite (Cretaceous)-Includes mostly highlyleucocratic muscovite-biotite monzogranite and some minoramounts of felsic muscovite granodiorite and episyenitic-alteredmuscovite-biotite monzogranite. Some facies are fluorite bearing.Porphyritic variants contain as much as 5 percent quartzphenocrysts. In places, contains very weakly defined primary layeringof dimensionally oriented potassium feldspar and biotite8 Sedimentary rocks, undivided (Paleozoic)-Includes Cambrian TapeatsSandstone, Bright Angel Shale, and Muav LimestoneIYdb I Diabase (Middle Proterozoic)-·Includes normally zoned laths ofplagioclase set In very fine grained matrix of granules of opaquemineral(s) and clinopyroxene. Close to chilled margins of some&esh outcrops of undeformed diabase. olivine is found in concentrationsof as much as 10 volume percent. Small masses of finegraineddiabase crop out sporadically in Early Proterozoic igneousand metamorphic rocks. Most extensive exposures are about 2 kmeast of Gamet Mountain. Subophitlc textures are dominant. Lowerchilled margins of some sills contain sparse hornblende and biotitemicroveinlets. Presumed to be correlative with the diabase ofSierra Ancha, Ariz., having an emplacement age of 1,150 Ma(Silver, 1963)IXpm I Porphyritic monzogranite of Garnet Mountain (Early Proterozoic)­Includes conspicuous. large potassium feldspar phenocrysts, setin a Iight·pinkish-gray, coarse-grained hypidiomorphic ground·mass. Many exposures show tabular phenocrysts as much as 10cm long. Some phases are predominantly subporphyritic seriateand show an almost continual gradation in size of their euhedralpotassium feldspar phenocrysts. Most widely exposed mass cropsout in the general area of Garnet Mountain, in the southeasternpart of the area, and extends discontinuously from there to northalong the low hills leading to Grand Wash Cliffs. Dated by Wasserburgand Lanphere (1965) to be about 1,660 Ma