Geologic map of the Middleburg 7.5-minute quadrangle, Vance and Warren Counties, North Carolina

North Carolina Department of Environmental Quality North Carolina Geological Survey Kenneth B. Taylor, State Geologist Equal-Area Schmidt Net Projections and Rose Diagram Plots and calculations created using Stereonet v. 8.6.0 based on Allmendingeretal. (2013) and Cardozo and Allmendinger (2013) Allmendinger, R. W., Cardozo , N. C., and Fisher, D., 2012, Structural Geology Algorithms: Vectors & Tensors: Cambridge, England, Cambridge University Press, 289 pp. Cardozo, N., and Allmendinger, R. W., 2013, Spherical projections with OSXStereonet: Computers & Geosciences, v. 51, no. 0, p. 193-205, doi: 10. 1016/j.cageo. 201 2.07.021 Equal-Area Schmidt Net Projection of Contoured Poles to Foliation (Shear, C or C’, Regional, etc) Contour Interval = 2 sigma N = 609 Equal-Area Schmidt Net Projection of Contoured Mineral, stretching and Aggregate Lineations Contour Interval = 2 sigma N = 62 Unidirectional Rose Diagram of Joints N = 74 Outer Circle = 15% Mean vector = 315 degrees This Geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program North Carolina Geological Survey Open File Report 2016-04 ^ ZPwms / ZPum ZPwms ZPwms CZvbm MB07-487, MCsc. CZvbm / \ uumi M«i MCsc MCsc ZPwms' CZvbm ^SallkbvilY ZPwms MCsc CZvbm' CZvbm ZPmbs ZPmbs Manson ZPmbs ZPmbs ZPwms л fWT Geology mapped 2004 - 2005 by Stoddard in southern half of quadrangle. Geology mapped 2006 - 2007 by Blake and Buford in northern half of quadrangle. u xajM ' / X; t if Г / Ab* ш i f ^ H j m lv / У \ / / t'. —cSlUa ! r /' ~>Д /j/ J • • \ UTM GRID AND 1982 MAGNETIC NORTH DECLINATION AT CENTER OF SHEET SCALE 1:24 000 1 0.5 0 1 i — i i — i I - 1 I — I I — I I - I MilHs 1,000500 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 1 0.5 0 1 I— I I— I I — I I — l I — I I — — I KilcmiKlKis CONTOUR INTERVAL 10 FEET OXIDES IN PERCENT SELECTED ELEMENTS IN PPM Sample ID Unit Name Map Unit Si02 ТЮ2 AI203 Fe203 MnO MgO CaO Na20 K20 Cr203 LO Sum АЯ As Au Ba Ce Co Cu Nd Ni Sc Sr Та Y Zn Zr MB07-487 Foliated felsic gneiss CZfgf 73.7 0.13 14 3 1.08 0.02 0.22 0.61 3.88 4.71 <0 01 0.94 99.6 <1 <1 <1 21 19.2 2 <5 86 <5 0.7 211 0.4 3.5 24 67.7 Powder mitirtul |1пнччмпц «nulucicd ill the Petrology Prvpiinilion Lithonilorv оГ the Pcpnilnu'ni «Г Urography and Urologs ill ihc lihrnKi of North Ciirolinn Wilmington. I .roi In- mi> 1 1 nnnl)*r« omiplrird hjSfiS Mhirrak Toronto. ( nnaiti for III nml 19 Imre rlrmrnl* ( 15 Imre elrmrnl* irpoilrd In table). Whole-nick «плМс» n«lng method rode* XRK767. » 75V, IMS95A, and FA 150.1, nnd IniUvklon I element method rode И MSI 211 fnrTa. NA - So «атрк япн1>«и PPM -parti |ht million Mil - lo«« он ignition Lake Gordon Fault Zone Nutbush Creek DESCRIPTION OF MAP UNITS Qal — 7 A. Jd - 7 - /^Jd; MCsc Pwg ZPpg ZPfg ZPwms CZfgf ZPahg ZPmbs CZvbm CZvt CZvtf Qal - Quaternary alluvium: Unconsolidated, poorly sorted and poorly stratified tan to light gray stream deposits of gravel, sand, silt, and clay. Jd - Olivine diabase dikes: Steeply dipping to vertical, gray to blue-black, slightly to severely weathered, fine to medium crystalline, locally plagioclase-porphyritic olivine diabase. Jd2 - Two-pyroxene diabase dike: Steeply dipping to vertical, gray to black, medium grained and typically plagioclase porphyritic two- pyroxene + quartz diabase. MCsc - Cataclasitic fault zone: Silicified and highly fractured zone containing mm to cm scale silicified angular clasts. Extensional veins of rhombohedral quartz prisms and local epidote common. Silicified and epidotized clasts of granitic gneiss locally preserved. Considered to be Mesozoic or Cenozoic in age. Raleigh Terrane Pwg - Biotite granite: Leucocratic (Cl less than 15), orange-tan to gray-tan, medium to coarse-grained, locally porphyritic biotite +/- epidote granite and sparse weakly porphyritic biotite + garnet leucogranite. Locally crosscuts foliated biotite granite. Locally contains enclaves of ultramafic-mafic rocks and of biotite-hornblende gneiss (ZPpg). May be part of the Wise pluton. Pg, - Foliated granitic mylonitic gneiss: Leucocratic (Cl less than 5-15), pink-tan and white-gray-tan, fine- to coarse-grained, but dominantly medium-grained, well foliated and lineated, white mica ± biotite granitic gneiss and leucogranitic gneiss, and biotite +/- white mica granitic gneiss. Some domains vary in biotite and white mica content in chiefly a pink-white microcline, plagioclase, and quartz matrix and may represent earlier enclaves or later intrusive granitoids, resulting in a streaky, banded or gneissic appearance. Mylonitic and ultramylonitic overprint obscures contact relationships. Flattened and rotated K-feldspar porphyroclasts form composite S-C surfaces and C-shear bands. Intruded by multiple generations of white to pink-gray-white pegmatite dikes and sills. Locally contains amphibolite, hornblende gneiss, and biotite schist enclaves. Lies between the Nutbush Creek and Lake Gordon mylonite zones. Pg2 - Foliated granitic rocks 2: Medium to coarsely crystalline and often megascrystic, porphyroclastic, strongly foliated, blue-gray to gray-tan, leucocratic to rarely mesocratic, biotite ± white mica granite and leucogranite, locally with allanite, and biotite ± white mica granitic gneiss and leucogranitic gneiss. Commonly protomylonitic to mylonitic and ultramylonitic. Lies within the Lake Gordon mylonite zone. Pg3 - Foliated granitic rocks 3: Medium crystalline, tan-gray to blue-gray, leucocratic to mesocratic, well foliated biotite + white mica metagranitoid and white mica ± biotite ± garnet leucocratic metagranitoid. Commonly protomylonitic to mylonitic and porphyroclastic. Also includes mylonitized pegmatitic to coarsely crystalline, porphyroclastic white mica ± biotite + quartz + feldspar metagranitoid sills, presenting a migmatitic appearance. Lies within the Lake Gordon mylonite zone, and locally contains enclaves of white mica schist (CZwms) near their mutual contact. Pg - In cross section B-B' only. Interpreted pods of granitoid in ZPwms unit. ZPum - Ultramafic rocks: Hypermelanocratic to melanocratic (Cl greater than 65), green to black-green interlayers of massive, coarse¬ grained actinolite talc schist and medium-grained metagabbro. Locally associated with epidote-quartz rock. Occurs as meso- and macro¬ scale pods or enclaves in ZPfg, ZPpg, ZPwms and Рдз. ZPpg - Porphyroclastic plagioclase biotite hornblende gneiss: Mesocratic (CI-35-45), black-gray to blue-gray, medium grained to porphyroclastic gneiss. Locally contains clinopyroxene and/or epidote. Biotite and hornblende define a foliation associated with mm-scale plagioclase and quartz compositional layers and larger plagioclase porphyroclasts. Local grain size variations in part due to mylonitic overprint. ZPfg - Felsic Gneiss: Leucocratic (Cl less than 5-10), orange-gray and white-tan, dominantly very fine to fine grained, well foliated, white mica quartzofeldspathic gneiss. Minor compositional layers vary in biotite and white mica content in chiefly a microcline, plagioclase, and quartz matrix. Commonly streaky or gneissic. Mylonitic and ultramylonitic overprint obscures protolith relationships. ZPwms - White mica schist: Medium-fine to medium crystalline, gray to gray-tan, strongly foliated and lineated white mica + sillimanite + garnet schist, medium crystalline, strongly foliated and lineated, green-gray, white mica + chlorite ± sillimanite ± garnet schist, white mica + biotite schist, and very rare crenulated white mica + kyanite + corundum schist. Sillimanite is commonly overgrown by white mica and helps to define the foliation plane. Contact with ZPfg is often transitional. Flattened and rotated quartz and feldspar commonly occur as porphyroclastic aggregates forming composite S-C surfaces along with C’ foliations defined by white mica. Typically intruded by pegmatitic to coarsely crystalline, porphyroclastic white mica ± biotite + quartz + feldspar gneissic metagranitoid sills that are locally migmatitic. Locally includes small bodies of leucogranite. CZfgf - Foliated felsic gneiss: Leucocratic (Cl less than 2), dark to light pink-red-orange, fine- to coarse-grained felsic protomylonitic, mylonitic, and ultramylonitic granitic gneiss. Variably foliated and lineated, and locally containing relict red-orange K-feldspar porphyroclasts and pegmatitic K-feldspar and quartz layers and boudins. Forms resistant lakeside outcrops and fields of cobbles and boulders that are highly fractured. Outcrops are reminiscent of the Ruin Creek Gneiss or Falls Leucogneiss between Henderson and Raleigh. ZPahg - Amphibolite and hornblende gneiss: Mesocratic (CI-50), blue-green-white to gray-green, foliated and lineated, medium¬ grained gneissic rock having compositional layers of darker amphibolite and lighter quartzofeldspathic hornblende gneiss. Occurs as local outcrops in Pg1 interpreted to be enclaves. ZPmbs - muscovite - biotite schist: Medium-grained muscovite - biotite schist, locally with chlorite or sillimanite and commonly quartzofeldspathic. Occurs as float and sparse saprolitic exposures representing enclaves within Pg1 . Present in cross section B-B' only. Carolina Terrane CZvbm - Chlorite-white mica phyllonite, mylonite, and ultramylonite: Light greenish-gray to dark green, foliated and lineated phyllitic rocks derived primarily from tonalite and granite of the Vance County pluton. Includes chlorite and sericite protomylonite through ultramylonite and phyllonite that form distinctive relict igneous and high strain compositional layers. Iron and manganese oxide commonly coat fractures and foliation surfaces. Flattened and rotated polycrystalline aggregates of plagioclase and quartz are common as porphyroclastic minerals that form composite S-C and C’ foliations. Quartz, feldspar, chlorite, and white mica contribute to a mineral aggregate, mineral stretch, and slickenline lineation. White mica and chlorite form conspicuous asymmetric fish structures ranging from mm to meters in scale. CZvt - Vance County tonalite: Mesocratic (Cl greater than 10-20), intermediate gray-blue-green, and coarse-grained metamorphosed biotite ± hornblende tonalite and minor granodiorite. Commonly forms medium- to coarse-grained boulder outcrops. Granular saprolite and saprock lakeshore exposures display a reddish salt-and- pepper appearance, and horizons of pure magnetite are common. Biotite phenocrysts ± mm-scale prismatic hornblende join rounded to tabular, saussuritized and sericitized pale green plagioclase and gray to distinctly cobalt-blue quartz phenocrysts and give fresh outcrops a gray-blue-green tint. Locally contains foliated and unfoliated enclaves of fine-grained chlorite phyllite, metagabbro, and metadiorite. Cut by mm- to meter-scale metamorphosed trondhjemite, monzonite, and granodiorite dikes. CZvtf is a high-strain equivalent of CZvt in the Nutbush Creek Fault Zone. EXPLANATION OF MAP SYMBOLS CONTACTS, FAULTS, AND OTHER FEATURES - location known diabase concealed - inferred diabase inferred . concealed diabase location known - cross section Faults - Solid where location known, dashed where inferred, dotted where concealed. For normal brittle faults, D indicates downthrown side, U indicates up thrown side. The tick mark indicates dip of fault plane. Zones of late brittle fracture and/or faulting; characterized by vuggy quartz and local brecciation indicated by dashed X lines. In cross section, for ductile strike-slip faults, the circle with an X indicates movement away from the observer, the circle with a dot indicates movement towards the observer. LINEAR, PLANAR, AND POINT FEATURES Strike and dip of inclined diabase or pegmatite dike or of quartz vein Strike and dip of inclined regional foliation within dike or sill X Bearing and plunge of crenulation lineation X Strike of vertical diabase or pegmatite dike or of quartz vein Strike and dip of inclined regional C or C' foliation X Bearing and plunge of mineral lineation Strike and dip of inclined dike or sill X Strike of vertical regional C or C' foliation X Strike of vertical dike or sill Strike and dip of inclined regional foliation (Srs) ee Strike and dip of inclined regional 65 X X foliation (Srs) (multiple observations at one location) X Strike of vertical regional foliation (Srs) X Strike of vertical regional foliation (Srs) (multiple observations at one location) Strike of dip of inclined foliation in enclave Strike and dip of biotite foliation in granitoid 66 Strike and dip of inclined 78^/ у regional C or C' foliation (multiple observations at one location) Strike and dip of inclined foliation in enclave 70y Strike and dip of inclined ' fracture surface X Strike of vertical fracture surface Strike and dip of inclined fracture surface (multiple observations at one location) X Strike of vertical fracture surface (multiple observations at one location) 76 X Strike and dip of axial surface of fold X Bearing and plunge of mineral aggregate lineation X Bearing and plunge of mineral stretch lineation X Bearing and plunge of minor fold hinge # Diabase station location © Station location /K‘ Abandoned mine or prospect Indicates location of vuggy quartz or sliceous breccia float MB07-487 0 Geochemical station location 1:24,000 SCALE CONTOUR INTERVAL 10 FEET WNW Nutbush Creek ESE Base topographic map is digital raster graphic image of the Middleburg 7.5 minute USGS quadrangle (1970, revised 1982). Disclaimer: This Open-File report is preliminary and has been reviewed for conformity with the North Carolina Geological Survey editorial standards or with the North American Stratigraphic Code. Further revisions or corrections to this open file map may occur. This geologic map was funded in part by the USGS National Cooperative Geologic Mapping Program under StateMap (Awards - 2004, 04HQAG0059; 2005, 05HQAG0082; 2006, 06HQAG0033). cross section scale - approximately 1 :24,000 no vertical exaggeration Geologic Map of the Middleburg 7.5-minute Quadrangle, Vance and Warren Counties, North Carolina By Edward F. Stoddard, David E. Blake and Christopher L. Buford Digital representation by Michael A. Medina and Philip J. Bradley 2016 Scan with smartphone for link to GeoPDF of map. Third party App required. Middleburg 7.5-minute Quadrangle, Open File Report 2016-04