Refractory minerals (pyrophyllite, andalusite), mining, processing and uses from paleohydrothermal centers Hillsborough and Efland 7.5 minute quadrangles, Orange County, North Carolina

Refractory minerals (pyrophyllite, andalusite), mining, processing and uses from paleohydrothermal centers Hillsborough and Efland 7.5-minute quadrangles, Orange County, North Carolina Kenny Gay, North Carolina Geological Survey ABSTRACT Recent detailed field mapping of Proterozoic metavolcanic rocks in the Hillsborough and Efland 7.5-minute quadrangles has shown a close relationship between the pyrophyllite ore bodies and paleohydrothermal centers. Bedded, quartzite-like rocks with a distinct hot spring texture, exist just west of the current mining operation. Three distinct units can be seen in outcrop, a lowermost thick-bedded massive quartzite-like siliceous rock is overlain by a medium bedded quartzite-like rock mixed with radial pyrophyllite rosettes. The uppermost unit is a distinct bedded siliceous rock consisting of bedded round nodules of fine-grain quartzite. A large lenses-shaped body of pyrophyllite and andalusite is being exploited by Piedmont Minerals, a division of Resco, Inc., in Hillsborough, North Carolina. The ore body parallels the regional strike of the metavolcanic and sedimentary rocks. The ore body contains, pyrophyllite, quartz, andalusite, diaspore, topaz, sericite, lazulite, pyrite, rutile, and secondary phosphate minerals. Numerous cubic molds of pyrite crystals are now partly filled with iridescent goethite. The pyrophyllite and andalusite are processed at the mine site. The high alumina refractory minerals are then transported to Greensboro, North Carolina. In Greensboro a new kiln has recently started operation to produce refractory bricks and blocks. The amount of Al203used in the bricks and blocks ranges from 33.3% to 51 .1%. The pyrophyllite and andalusite are desirable due to their chemical inertness, high dielectric strength, high melting point and low electrical conductivity. The use of the high alumina minerals decreases the thermal expansion and moisture expansion of the product during high temperature service, provides excellent volume stability and resistance to deformation at high temperatures, increases the firing range of the blocks and therefore decreases firing shrinkage, and increases the strength of the fired blocks and bricks. Site location map - (above) - Orange County, North Carolina is highlighted to show location. Andalusite (blue) in massive pyrophyllite - (left) - from the Piedmont Minerals Co., Inc.’s, Hillsborough Mine; (below) - enlarged view showing andalusite crystals (blue). Plate I. Bulletin 80 Orange County, N.C ж Mines tt Abandoned mines x Prospects C N. C. PYROPHYLLITE MINES & PROSPECTS L _ 1. Daniels Mountain 2. Bowlings Mountain 3 Robbins prospect 4. Jones prospect 5. R.E. Hilton property 6 E.C.Hilton property 7 Robbins-Uzzell property 8. Robbins prospect no 2 9. Murray prospect I0 Hillsborough mine l-Teer prospects I2 Snow Camp mine I3. Major Hill prospect 14 Hinshaw property 1 5 Staley deposit 16. Pilot Mountain prospecls 17. McConnell prospect PYROPHYLLITE DEPOSITS IN NORTH CAROLINA I8. Jackson prospect I9 Bates mine 20- Phi Mips mine 21.Womble mine 22. Reaves mine 23. Jones prospect 24. Currie prospect 25. Ruff prospect 26. Hallison prospect 27 Standard Mineral Co 28. Tucker 6 Williams pits 29. Sanders prospect 30. Ammons mine 31. North State property I 32.North State property 2 33. Cotton Stone Mtn 34.Standard Mineral Co Pyrophyllite deposits in North Carolina - (above) - from Stuckey, J.L., 1967, Pyrophyllite deposits in North Carolina: North Carolina Geological Survey, Bulletin 80. Sulphide-rich zone - (left) - pyrite crystal molds filled with goethite. Radial pyrophyllite - (right) - outcrop in Efland 7.5-minute quadrangle, NC. Close up view of image above - (right) - Outcrop detail of silicified hot spring deposit west of the Piedmont Minerals Co., Inc.’s, Hillsborough Mine. Outcrop view of silicified hot spring deposit - (left) - outcrop is west of the Piedmont Minerals Co., Inc.’s, Hillsborough Mine. Field staff scale interval is 0.5 feet. Photomicrograph of silicified rock - (right) - west of the Piedmont Minerals Co., Inc.’s, Hillsborough Mine - 1 0x magnification. Refractory brick - (right) - finished product at Resco’s new Greensboro, N.C., kiln. Refractory brick - (left) - leaving Resco’s new Greensboro, N.C., kiln. HILLSBOROUGH 7.5-MINUTE GEOLOGIC MAP, ORANGE COUNTY, NORTH CAROLINA DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES DIVISION OF LAND RESOURCES This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program NORTH CAROLINA GEOLOGICAL SURVEY OPEN FILE REPORT 2005-02 GEOLOGIC MAP OF THE HILLSBOROUGH 7.5-MINUTE QUADRANGLE, ORANGE COUNTY, NORTH CAROLINA BY PHILIP J. BRADLEY AND NORMAN K. GAY Digital representation by Michael Л. Medina and Philip J. Bradley 2005 DESCRIPTION OF MAP UNITS Zft-g Zdlt-purple Zmt/ml Zadlt Zmt/ml Zgd-porphyritic Zmt/ml Zgddi-b Zmt/ml Zdlt Zml/mt Zgddi-b (Iporphyritic Zml/mt Zft-purple Zft-g Zgddi-b Zadlt m4 Zadlt Zmt/ml ^Zadlt Zaft Zmt/mU ® Trq-breccia Zadlt Zmst Zdi/gd Jd Zfs-cong si Zml ' Zft-cong Zdlt Zadlt Zdi/gd Zadlt Zmst Zdi/gd Zmst Zmst Zmst Zmst Qal Zmst Unidiitftional Rose Diapain of Pi unary Layering. Bedding. Welding Compaction Foliation, and Flow Banding N=305 Unidiiectional RoseDiagiain of Joints N=822 References for Map S'teieonet • Con touted Poles to Foliation, Cleavage. Spaced Cleavage, and Shear Foliation N=454 Unidiiectional Rose Diagiam of Foliations. Cleavage. Spaced Cleavage, and Shear Foliations N=454 CONTACTS Litliologic contacts - Disfiibution and conccntiation of stiuctuinl symbols indicates dcgicc of ichability - geologic contact concealed geologic coirtact . concealed fault fault - D indicates dowutliown side. U indicates iiptluown side anti form ■ A' a oss section lagli stiani zone SEDIMENTARY UNITS Qal - Alluvium Unconsolidated clay, silt, sand and gravel to cobble-sized clasts, subroinided to angular, deposited ui drainages Qcv - Colluvium: Accumulations of angular cobbles and boulders INTRUSIVE AND META-INTRUSIVE UNITS Jd - Olivine diabase: Black to greenish-black: fine- to medium-grained: dense: consists primarily of plagioclase. augite. and olivine Occurs as dikes up to 80 ft wide Diabase typically occurs as spheriodally weathered boulders with a grayish-brown weathering rind. Red station location indicates outcrop or boulders of diabase. Zgd - Graiiodiaite Exhibits a variety of cola s and textures ranging frail grayish-white, fine- to medium-grained hornblende granodiorite: pinkish-white, medium-grained hornblende granodiorite: and gray, fine-grained granodiorite. Zgd-fme - Fine-grained granodiorite Light-gray to green, ranges from equigranular very fine-grained granodiorite to very fine-grained papliyritic graiiodia ite w ith plagioclase phenociysts (1 nun to -4 nun) Black colored ampliibole. when visible, occurs as phenociysts (< 1 nun to 1 nun) and as intergrowths with plagioclase: ampliibole intergrowths distinguish rock from fine-grained tuffs Zgddi-b - Granodiorite and diorite Composite phitai of dominantly medium-grained, hornblende granodiorite: lesser amounts of medium-grained hornblende diorite. fine-grained granodiorite. and diorite. Unit caitains abundant xenolidis of volcanic rock and enclaves!?) of fine-grained granodiorite to diorite. Zdigd-b - Diorite and granodiorite Composite phitai of dominantly medium-grained hornblende diorite. lesser amounts of medium-grained hornblende granodiorite. fine-grained granodiorite. poiphyntic diorite with plagioclase phenociysts. minor amounts of poiphyntic granodiorite with plagioclase phenociysts. porphyritic granodiorite with potassnun feldspar phenociysts, and gabbro. Unit caitains abiuidant xenohths of volcanic rocks and enclaves!?) of fine-grained granodiorite to diorite. Zgd-porphyritic - Poiphyntic granodiorite Greenish-gray with a pinkish-hue: amphibole-bearing. porphyritic granodiorite with plagioclase phenociysts. Plagioclase phenociysts are green from saussuritizatiai and range from 2 to S nun m a matrix of veiy fine-grained quartz and alkali-feldspar. Weathered surfaces exhibit a distinct strongly porphyritic texture. Porphyritic rhyolite of Newton (1983). Zgdgr-p - Graiiodia ite and granite of Piney Mountain Creek area: Canposite pluton of dominantly niediiun-grained hornblende graiiodiaite with lesser amounts of medium-grained hornblende granite Zdi - Diorite Greenish-gray to gray, medium-grained: equigranular: hanblende diorite Major minerals include plagioclase and hornblende Greenish-white plagioclase crystals canpose up to 50% of the rock and are typically serialized and saussiu itized Zdigd - Diorite and granodiorite: Small plutomc bodies of dominantly medium-grained hornblende diorite with lesser amounts of medium-gramed hanblende graiiodiaite. Zgb - Gabbro: Fine-grained pyroxene gabbro dike METAVOLCANIC UNITS Ze p - Mixed epiclastic-pyroclastics: Grayish-green to greenish-gray: tuffaceous; sandstones, siltstaies and minor phyllite The siltstones typic ally are weakly pliyllitic Unit contauis lesser amounts of coarse tuff and lapilli tuff. Zaft - Altered felsic tuffs Very light-gray, light-greenish-gray to white, with red and yellow mottling: altered, felsic tuffs Alteratiai of felsic tuffs have produced sericite-quartz phyllite. pods of pyrophyllite. and quartz + pyrophyllite rock: all with conunon 1 nun to 2 nun diameter cubic pyrite aggregates and goethite-hned molds of pyrite crystals Fine-grained poiphyrob lasts of clilor itoid (■ 1 nun) and andalusite (up to 4 nun) are present ui some pyrophyllite bearing rocks Relict litluc clasts and kaoluutized feldspar crystal shards are visible in some outcrops. Relict structures are obliterated in heavily altered rocks Mapped area contains boulders, up to several feet in diameter, and aitcrops of massive milky quartz and quaitzite-hke rock. Occaieechee Mountain contauis abiuidant white, beige, to reddish and tan: massive: sugary to porcelaneous: vay fine- to mediiun-grained quartzite-like rock Quartzite-like rock is often mixed with micaeous senate phyllite The micaeous sericite phyllite gives die othawise massive quaitzite-hke rock a foliation Zmst - Matrix suppated tuffs Greai-gray to green, w eakly foliated to well foliated: matrix supported, polymictic. lapilli tuffs and tuff breccias. Angular to sub-rounded. Iitlnc fragments range from 1 nun up to 1 m diametei Unit is interpreted as a resedimented syn-eruptive volcanic lastic deposit m which texturally unmodified voicanidastic debris and entrained texturalh more mature accidaital clasts are mcorporated into a rapidly resedimented package of sediment May be emplaced via submarine mass flows, subaerial landslides and a lahars. Outcrop in Few's Ford area of Elio River State Park has been interpreted as a laliar deposit (Allen and Wilson. 1968 and Rochester. 19"8). Zft - Felsic tuffs: Gray-green to green, massive to foliated coarse tuff and lapilli luff. Locally plagioclase crystal-fragment-rich coarse tuffs are present Zft-m - Felsic tuffs west of Ml Hainan Church Grayish-green to greenish -gray; massive to foliated, thin to thickly layered fine to coarse tuff with lessa amounts of lapilli tuff 1-5% accessory sulfide minerals commonly present Outcrops and boulders typically display a white w eathering rind Zft-c - Felsic tuffs of the Code quany area Greenish-gray, massive to strongly foliated, daise. plagioclase crystal-fragment-rich coarse tuffs. Strong foliation is intapreted to be result of primary volcanic welding and or compactiai 1-5% accessay sulfide mmerals commonly present. Outcrops and boulders typically display a white weathering rind. Zft-f - FeLsic tuffs of the Few's Ford area: Dominantly light-green to dark-green: massive to weakly foliated coarse tuffs. Interlayered with light-gray to gray; massive to weakly foliated lapilli tuff; a distinctive purple-colored coarse tuff; polymict caiglomerate (Zft-caig). and dark-gray to black, ciyptocrystalline lava similar in appearance to the lavas present in the Zadlt unit 1-5% accessory sulfide minerals commonly present. Zft-cong - Conglomerate interlayed in felsic tuffs of Few’s Fa d area (Zft-f) Caiglomerate composed of subrainded to rounded: polymictic clasts (up to 4 cm) Clast types include graiiodiaite and diorite. black, papliyritic lava with plagioclase phenociysts: and fine to coarse tuff Zft-p - Felsic tuffs west of Piney Grove Damnantly gray to green-gray: massive to weakly foliated: layered in places coarse tuff' with lessa- amounts of lapilli tuff Mina mta layers of voicanidastic sandstaie and thinly bedded (possible burrowed!?)) siltstaie are present 1-5° о accessory sulfide minerals commonly present especially near contact zone with the Buckwater Creek plutai Zft-t - Felsic tuffs east of Temple of Truth Church Green to gray-greai. massive to weakly foliated, layered in places coarse tuff with lesser amounts of lapilli tuff Plagioclase crystal fragments compose 1-5% of typical sample Zft-s - Felsic tuff's of die St Mary's Church area: Gray-green to gray: massive to weakly foliated coarse tuff with lessa- amaints of lapilli tuff. Minor interlayers of very thinly bedded coarse tuff Crystal fragments, when present, are dominantly plagioclase. Clast types include black, poiphyntic lavas with plagioclase phenociysts similar to the Zdlt lavas and gray fine tuff clasts Zft-b - Felsic tuffs of the Blackwood area Green-gray to gray coarse tuff and lapilli tuff Plagioclase crystals and crystal fragments are common. Litluc clast types includes dark-gray to black, magnetic: 1 to 20 nun. ciyptocrystalline lava, or clasts of papliyritic lava with feldspar phaiociysts. Papliyritic clasts are idaitical to the papliyritic phases of mill Zdlt. Outcrops and thui sectiais show a prominent welding and or compactiai foliation with fianune-shaped clasts. Outcrops typically occiu as vay resistant fin-like outcrops Zft-g - Felsic tuffs of the Governor Burke's Grave area: Damnantly gray, greenish-gray, grayish-green; massive to strongly foliated, fine to coarse tuff and lapilli tuff Plagioclase crystal fragniait-rich coarse tuff and litluc lapilli tuff are caiunon Mina interlay as of strongly foliated muscovite saicite phyllite. welded compacted lapilli tuft's with glassy eye-shaped quartz: and altered tuffs Map scale inter layers of apparait epic lastic rocks (Ze p) are present in imit Zft-purple - Purple felsic tuffs Light-piuplish-gray. reddlsh-hght-piirple. and gray, slaty cleavage parallel to bedding: mad ix supported; polymictic lapilli tuff and tuff breccia. Interlayered with plagioclase- and quartz -crystal coarse tuff: welded tuff, quartz-crystal tuff: and slatey argillites Litluc clast types include: angular, sericite-rich rock flattened parallel to the foliation; black, subangular to subrounded. porphyritic lava with plagioclase phenociysts: and green, stibangular. mafic tuff and or lava. Plagioclase occurs in dace to minor amounts as angular fragmaits of crystals up to 3 nun in size Welded phases of this unit caitain flattened relict pumice fragmaits that are now altaed to chat-like quartz. Zgfll - Gray felsic tuff' of the Cates Creek area Gray to dark-gray: massive to foliated fine to coarse tuft' Rare plagioclase crystal fragments are present. 5-10% accessay sulfide minerals commonly present Rock is relatively featureless Zgfl2 - Gray felsic tuft's of die upper Little Creek area Gray to ligiii-greenish-gray; massive to foliated fine tuff 1-5° о accessay sulfide niinaals conunonlv presait Zq - Quartz bodies White, beige, red. and tan: sugary to porcelaneous: vay fine- to medium-grained quaitzite-hke rock Outcrops are usually massive Quartzite-like rock is occasiaially mixed with sericite and or pyrophyllite. The addition of sericite and a piyophylhte gives the otherwise massive quaitzite-like rock a foliation Pyrite is presait as cubic crystals and empty cubic molds of crystals (up to 12 nun). Map areas caitnui boulders (up to several feet in diameter) and outcrops of white colored massive quartz Zdlt - Dacitic lavas and tuffs Distinctive dark-gray to black, siliceous: cryptociystalhne lava, poiphyntic lava with plagioclase phaiociysts. and flow banded dacitic lavas Interlayered with gray to black, welded and nai-welded coarse tuff and lapilli tuff. Tuffs oftai contain black-colored fianune. lip to 10 cm, inteipieted as flattaied pmnice Clast types include black cryptociystalluie lava and papliyritic lava with plagioclase phaiociysts Dift'aentiatiai betweai lavas and massive tuffs is difficult in hand sample ui most cases The lavas are interpreted to have been coherent magma that were extrusive a vay shallow intrusions associated with dacite domes Tuff' interlayers are intapreted as episodic pyroclastic flow deposits and air fall tuffs generated during eruption of domes Zdlt-purple - Dacitic lavas with distinctive ptuple cola Reddish-light-puiple to lilac-colored, massive, miciociystalline to cryptociystalhne; poiphyntic dacitic lava with plagioc lase phaiociysts Zadlt - Andesitic to dacitic lavas and tuft's of Poplar Ridge area Distinctive black, siliceous; massive; cryptociystalluie lava, poiphyntic lava with plagioclase phenociysts (up to 4 nun), and flow banded lava with local ainygdules. Interlayed with the lavas are gray to black, welded and nai-welded. coarse tuff, lapilli tuff, and tuff breccia Tuffs range from massive to strongly welded tuff with fianune-shaped clasts up to 15 cm. Clast types include: black ciyptocrystalline lava and papliyritic lava with plagioclase phenociysts. The lavas and tuffs are veiy resistant to weathering and typically have a whitish-gray weathering raid Differaitiation betweai lava and massive tuff is difficult ui hand sample in most cases The lavas are intapreted to have beai coherent magma that were extrusive a vay shallow intmsiais associated with dacite to andesite domes Tuffs are intapreted as episodic pyroclastic flow deposits and air fall tuft's gaia ated during auptiai of domes Zml - Mafic lavas Green, gray-green, black: aiuygdaloidal basalt, porphyritic basalt with plagioclase phenociysts. and microcrystalline basalts. Inter layered with coarse plagioclase crystal tuff and coarse ampliibole crystal tuft' Basalts are interpreted to be lava flows or shallow mhusives The tuffs are fine-grained and caitain plagioclase crystal fragments, caiunaih- alta ed to epidote. and ampliibole crystals as 1-2 nun prismatic crystal fragmaits. Zinl-c - Malic lava of the Cun-ie Hill area Distinctive, very dark-gray to black, veiy fine-grained; magnetic, mafic lava( ’) hi thin section the rock is composed of a vay fine matrix of plagioclase latlis and apparent relict ainygdules in-filled with epidote and quartz Zml nit - Mafic lava and tuffs: Dominantly veiy dark-gray, greaush-gray. black: massive; andesitic to basaltic; inicrocrystallme lava, amygdaloulal lava, and papliyritic lava with plagioclase phenociysts. This mut contains inina- plagioclase crystal-fragment coarse tuffs and ampliibole crystal-fi aginait coarse tuffs Inteipieted pillow structures are presait in sane mafic lavas Zmt ml - Mafic tuffs and lavas: Dominantly dark -green, greaiish-gray. grayish-green; massive to foliated, fine and coarse tuffs of andesitic(?) to basaltic!?) composition. Unit uidudes crystal-free, fine tuffs, matrix supported: plagioclase- and amphibole-ciystal-fi agmait coarse tuff; and crystal-litluc lapilli tuffs. Clasts are subangular (up to 5 nun) and dark green Mina thui mafic lava flows with relict ainygdules and inteipi eted pillow structures are presait in unit. FAULT ROCKS Trq-breccia - Quartz breccia White; massive to brecciated: vttggy quaitz Typically contains angular clasts of altered volcanic rock suspended in a quaitz matrix Some zones exhibit a lacey pattern of intersecting quaitz veins with a matrix of altered wall rock St я eon Я • Contour ed Poles ro Pnmniy Layering. Bedding. W elchng Compaction Foliation, and Flow Banding N=305 All pre-Mesozoic rocks of the Hillsborough quadrangle have beai metamoiphosed to at least the chlorite zaie of the greenschist metamapluc facies. Many of the rocks display a weak or strong metamoiplnc foliation Althaigh subjected to metamorphism, the rocks retain relict igneous, pyroclastic, and sedimentary textures and structures that allow for the idaitification of protolith rocks As such, the prefix "meta" is not included in the nomaiclature of the pre-Mesozoic rocks described in the quadrangle. The nomaiclature of the Intanatiaial Union of Geological Sciaices subcommission on igneous and volcanic rocks (JUGS) after Streckeisai (19?3 and 19?9) is used in classification and naming of the units. The dassificatiai and naming of the rocks Is based on relict igneous textures, modal mineral assemblages, or normalized nunaal assemblages when «hole-rock geochemical data is available Past «’orkers in die Hillsborough quadrangle (But la-. 1964. Allen and Wilson. 1968; Sykes. 1976. Black. 19 . and Newton. 1983) have used various nanaiclatiu e systems for die lgneais rocks The raw data of diese earlier workers was recalculated and plated on ternary diagrams and classified based on IUGS nomenclature. Pyroclastic rock terminology follows that of Fisher and Sclinunke (1984). ~9 0(T 36 0*'30" Owe J \ J \ +- tMWttM ф MNittWIsmltt: / \ X МГЯ1СП 1W / \ ▼ Be* »C77 / ’ ♦ \* \\ / f J / \ *x\ v-»» \ v / / / \ - * 4 \ да in г «in* A * /. ' /. PlafkctoM Buckw.ilf Creek QAPPLOT OF NORMALIZED WHOLE ROCK ANALYSES OF PAST WORKERS DISTRIBUTION OF PRE-MESOZOIC- PLUTONIC ROCKS AND INFORMAL PLUTON NAMES S()() 1000 1500 Meters 124.000 SCALE CONTOUR INTERVAL 10 FEET Base toposiapluc map is digital raster aaplut ullage of die Hillsborough 7. 5 liiiuitc USGS qiiaibangle (1994). Noitii Carohua State Plane NAD S3 nictcis projection Research suppated by die U S. Gcologic.4 Survey. National Cooperative Geologic Mapping Piogiaiu, tuidci USGS award iiiiiibci 04HQAQ0059. Pie crews and coudusiais contained in Hus doctunent aie tliose of Hie million and slioidd not be inteipieted as uccessanh'icpicsciiluig the official policies, cillici expressed or implied, of Hie U.S. Government. Disclaimer Tins Open-File report is preliminary and has not been reviewed for conformity with the North Carolina Geological Survey editorial standards or with tire North American Stratigraphic Code Further revisions or corrections to tins preliminary map may occur prior tc lts release as a North Carolina Geological Survey map 1 5 Miles STRUCTURAL SYMBOLS Feet MN Г Qti V pninaiy betiding and lay ciing are at th X intersection point of multiple symbols ^itical pnniaiy bedding and la>-cnug N 2У stnke anti dip of Jcax-ngc / vertical stnke of clea\aage * V stnke and tfcp olpiinniv' ok.iu. conipactiou and oi welding >Ti1ical stnke of pnniaiy volcauc compaction and oi welding "4b 1 » MILS X V V stiikc and <hp of inctainoipiuc tohation X veitical stnke of inctainoipiuc tobation UTM 0F.C> AND 1994 UA ONE TIC NORTH DECLINATION AT CENTER OF SHEET V stnke and dip of joints / 'CI til Д I slllkc of joints- V stnke and tfcp of uitcijHctcd slieai foliation X \citKal stnke of inteipieted slteai foliation LOCATION OF THE HILLSBOROUCH 7 .5. MINUTE QUADRANGLE. NORTH CAROLINA 1-77 1-85 1-95 . 4 •' PM t — ■/ Л Aj- — j_26 n\y# / Л ~vT /7 Yi/ > i / x W5i l Y/ \ \ * M5 M у mo / / ology mapped October 2004 through August 2005 stnke and dip of spaced cleavage stnke and dip of quaitz vein bend and plunge of luicatioii bend and plunge of skckcnlinc luieation bend and plunge of sketching line ali on diabase obscn'atioii location observation station location Ф fault gouge vcitiial stnke of spaced cleavage <4nkc and dip ofpiunaiy vole mu v flow banding 31 b end and plunge of cicnulatiou fold axis 6 b end and plunge of f cicnulatiou lineation * *8 b end and plunge of fold lunge 5* active пенс abaiulaicil nunc Zdlt-purple Zadlt Zgft2 Qcv Zgd-fine Zgddi-b Zdigd-b Zgd- porphyritic Zgdgr-p Zdi Zdigd Ze/ p Zaft Zmst Zft-m Zft-c Zft-f Zft-cong Zft-b Zft-puiple Zft-s Zgftl Trq-breccia Zft-g Zdlt лир / Jd-« ЛГ Zft-purple Zmt/ml scale 1:24.000 no vertical cxaggei aliou ineasureinriil in feet Allen, EP . and Wilson. W F . 1968. Geology and mineral resources of Orange County. North Carolina Division of Mineral Resources. North Carolina Department of Conservation and Development. Bulieiin 81 . 58 p Butler. JR . 1964. Chanical analyses of rocks of the Carolina Slate belt. Southeastern Geology, v 5.p 101-111 Black. WAV. . 1977. The geochronology and geocheniistiy of the Carolina Slate belt of noith-caiti al Nath Carolina PhD thesis. University of North Carolina. Chapel Hill. 1 IS p. Fisher. R V and Schmincke H-U. 1984. Pyroclastic rocks. Berlin. West Germany. Springer- Verlag. 4" 2 p Newton. M.C.. 1983. A late Precambrian resurgent cauldron in the Carolina slate belt of Nath Carolina. USA. M S thesis. Virginia Polytechnic Institute and Stale University. 89 p Rochester. L L. 1978. A geologic investigation of die Cates fad [Fews ford] area. Orange County. North Carolina, unpublished Senior Thesis. University of North Carolina. Chapel Hill. 1 1 p Streckeisai. A L . 1973. Plutanc rocks: Classification and nomaiclature recommended by the IUGS subconmiissiai on die systanatics of igneais rocks Geotiines. v. 18. p 26-31 Streckeisai. A.L.. 19”9. Classification and nanenclature of volcanic rocks, lamprophyres, carbaiatites. and nielilitic Recanniaidaliais and suggestions of (lie IUGS subcaiunission on the systanics of igneous rocks. Geology, v 7. p 331-335 Sykes. M L . 1976. Pyrophyllite genesis in the Carolina slate belt A study of the Hillsba ough. North Carolina deposit. M S thesis. University of North Carolina. Chapel Hill. 52 p For additional information: Kenny Gay, North Carolina Geological Survey 1612 Mail Service Center Raleigh, North Carolina 27699-1612 919.733.2423 - http://www.geology.enr.state.nc.us .45 A A IV C. - - Г / 4 a