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—73— belt. Near Geraldton the finer—grained metasediments (Pye's group B) are disconformably overlain by conglomerate (Pye, 1952)\which is the lowermost unit of the upper metasedimentary sequenc (Windigokan or group A). The same general lithological changes havd been observed in the Beardmore area (Mackasey, 1969) but disconformble relationships have not been recognized. A mafic to intermediate volcanic unit overlies the upper (Wind— igokan) metagediments in the Beardrnore area. •3,. Origin The metasediments in the Beardmore—Geraldton belt thin and become coarser grained to the north. The metavolcanic rocks on the oiher hand, are thickest in the northern part of the belt and thin southward (Bruce, 1937; Macdonald 1942, 1943). Ayres (L969) suggested that the metavolcanic rocks of the Beard— more—Geraldton area were part of an east—trending metavolcanic arc that is now represented by the Keewatin belt. This arc developed in an older sedimentary basin within which metasediments of the Quetico belt were deposited Volcanism commenced with subaqueous extrusion of mafic to intermediate flows that built up submarine shield volcanoes. The flows interfinger southward with the metasediments of the basin. Later felsic pyroclastic volcanism built subaqueous to subaerial cones on top of the older mafic shield volcanoes, The change in sedimentation from relatively uniform fine— grained sand and silt to more heterogeneous, coarser grained gravel, sand, and silt corresponds to the initiation of major felsic volcanism and the emergence of the volcanoes above sea level. (Ayres, 1969) The coarser—grained metasediments of the upper metasedimentary formations contain abundant clasts of felsic to intermediate volcanic rocks. Figure 2 is a diagrammatic cross—section (after Ayres, 1969), showing the interfingerlng relationships existing between rqcks of the Keewatin and Quetico belts. Igneous Activity and Regional Metamorphism The metavolcanic—metasedimentary sequence has been intrudad by large felsic batholiths ranging in composition from granitic gneiss to quartz diorite. These batholiths form the north and south boundaries of the Beardmore—Geraldton belt. Relatively small lenticular bodies of mafic intrusives occur in the central part of the belt.
—74— Most of the metavolcanic—metasedimentary sequence has been metamorphosed to greenschist facies but metamorphic grade increases southward within the Quetico belt (Macdonald, 1942; Peach, 1951). Structure The early Precambrian metavolcanic—metasedimentary sequence has been isoclinally folded along east—trending axes. Detailed work by Elorwood and Pye (1955) and Pye (1952), based on surface and subsurface mapping and geophysical data, outlined the style bf folding in the Geraldton area. Several prominent east—trending faults have been recognized. The Paint Lake fault is a major structural discontinuity in the Beardmore area and marks a change in both lithology and structural style. South of the fault, interbedded metasediments and mafic metavolcanic flows are folded along east—trending axes, but to the north, intermediate to felsic pyroclastic rocks predominate and fold axes trend north and northwest. Late Precambrian Rocks Relatively flat—lying sedimentary and volcanic rocks uncon— formably overlie Early Precambrian rocks in many places along the north shore of Lake Superior. Rare exposures of conglomerate, sandstone, shale, and dolomite of the Sibley Group are present in the western part of the Beardmore—Geraldton area near Lake Nipigon. Keweenawan diabase forms north—trending dikes throughout the Beardmore—Geraldton area and flat—lying sheets near Lake Nipigon. A diabase sheet, 400 to 650 feet thick forms a cuesta just east of Beardmore. The sheet dips gently westward and at the Leitch Gold Mine, four miles west of Beardmore is 1871 feet below surface (Benedict and Titcomb, 1948; Ferguson, 1967). Porphyritic diabase dikes, locally known as "Greenspar porphyry" are thought to be older than the sheets and equigranular dikes. Late faulting has disrupted the Keweenawan diabase sheets and dikes and probably represents reactivation of older faults. Pleistocene Thick deposits of sand and gravel are present throughout the belt and in some areas outcrop is scarce. Spillway channels, and deltaic sand and valley train deposits have been outlined by Zoltai (1965). Wave—cut terraces and sand dunes are found near Lake Nipigon. ECONOMIC GEOLOGX Concentrations of gold, silver, iron, copper, nickel, molybdenum,
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-ç — — I: .t. F Geology Superi
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TABLE OF CONTENTS INSTITUTE DIRECTO
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-2- "P R 0 G R A M" Tate day, Ma9 5
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-4- SESSTOM 2 1.00 Business Meeting
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-6- F'viday, May Slit, 1970 Page No
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-8- SYNTHESIS OF EARLY PRECAMBRIAN
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-10- THE SOUTHERN ASSOCIATED PART O
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-12- THE STRUCTURE OF THE NORTHERN
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-14- MT. ST. JOSEPH - AN ARC}IAEAN
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-16- A MODEL FOR TECTONIC VARIATION
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-18- EARLY PRECAMBRIAN GEOLOGY OF T
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DEFORMATION OF THE SEINE CONGLOMERA
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-22- MINERAL POTENTIAL IN CREENSTON
Page 27 and 28:
-25-- ROOT SEVERANCE AND TECTONIC T
Page 29 and 30: -27- STRUCTURE OF ThE DULUTH GABBRO
Page 31 and 32: -29- 1. Department of Geology and G
Page 33 and 34: -31-. KEWEENANWAN COPPER DEPOSITS I
Page 35 and 36: —33- The youngest rocks in the ar
Page 37 and 38: -35- STRUCTURAL AN!) METAMORPHIC HI
Page 39 and 40: -37.- ARCHAEAN VOLCANIC STRATIGRAPH
Page 41 and 42: ______ __________ _____ IDEALIZED S
Page 43 and 44: —41- (3) The upper liimit of 30 p
Page 45 and 46: -43- Fjgire 2 The revised classific
Page 47 and 48: —45— EVIDENCE FOR A TROPICAL CL
Page 49 and 50: —47-- WIDESPREAD OCCURRENCE OF AL
Page 51 and 52: —49— PROTEROZOIC ROCKS IN THE T
Page 53 and 54: —51— Guide to the Proterozoic R
Page 55 and 56: WEST EAST f * . . .. . . S S S S 5S
Page 57 and 58: ________ — ;—=- — —-- —
Page 59 and 60: —53— The uppermost submember of
Page 61 and 62: —55— Morey notes that sediment
Page 63 and 64: —57— (c) layered mafic bodies,
Page 65 and 66: —59— DESCRIPTION OF STOPS Milea
Page 67 and 68: —6 P- Note downwarping of beds on
Page 69 and 70: —63— Note the lenticular chert
Page 71 and 72: —65— 0.0 From the intersection
Page 73 and 74: —67— STOP 16 In the roadcut to
Page 75 and 76: —69— ThE BEARDMORE-GERALDTON BE
Page 77 and 78: —72— the Quetico belt by Stockw
Page 79: —72 B— ABITIBI BELT —ø.jsour
Page 83 and 84: —76— SELECTED REFERENCES Anonym
Page 85 and 86: —78— Stockwell, C. II., 1964; F
Page 87 and 88: —80— ae DESCRIPTION OF STOPS 0.
Page 89 and 90: —82— STOP 8 (Paint Lake Fault).
Page 91 and 92: -84— Outcrops near the road are o
Page 93 and 94: —87— Guide to the Port Coldwell
Page 95 and 96: AGE RELATIONSHIPS The volcanosedime
Page 97 and 98: .• ____________________ . — .._
Page 99 and 100: -I- + -4.- -I- - - - - — - 4- ; E
Page 101 and 102: —93— (3) 'flow—layering' exhi
Page 103 and 104: GOSSAN ZONE IN SULPHIDE BEARING GAB
Page 105 and 106: —95— (3) feldspars variably fol
Page 107 and 108: —97— Fig. 6c Fig. 6b ;' TRAIL T
Page 109 and 110: Pig. 7 West contact of CROSS SECTIO
Page 111: PRINCE AR THUR HOTEL ® 0 ® SHOREL
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Program, Abstracts, and Guidebooks - University of Minnesota Duluth

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