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—88— laurvikites highest in the group are commonly porphyritic. Several zones are recognized within the main group. Upper Zone Lower Zone Inner Border Zone 'B' Inner Border Zone 'A' Outer Border Zone massive laurvikite layered laurvikite layered gabbro massive gabbro chilled gabbro The Secondary Group is composed of an older, saturated series which includes syenodiorites (Map Unit 4) and nordmarkites (Map Unit 5) and a younger, undersaturated, series with several varieties of feldspathoidal syeniie (Map Unit 6). Generally, within this group, rocks comprising the saturated series are peripheral to the felds— pathoidal syenites. Except for the feldspathoidal syenites, which are layered at some localities, the rocks Of the Secondary Group are massive and apparently structureless. The Secondary Group is characteristically associated with xenolithic bodies. Although widespread, these bodies are thought to belong to one large unit, the so—called Coubran Lake meta— volcanic cap. Common variants, generally gradational one to the other, include aphanitic amygdular and diabasic volcanics. The 'cap' rocks and the rocks of the Secondary Group are preferentially concentrated in that portion of the massif which is west of Wolf Camp Lake. (ref to Stop 3, Fig 4). It is noted that the 'cap' appears to be 'free—floating' in the north and 'attached' in the southern part1 These and other relationships suggest a near—roof situation of the present level of exposure. The Port Coldwell magma, which apparently contained solid plagioclase fledspar, was emplaced (1) from a probable source located to the SSW, (2) by a process of doming, stoping, and forceful injection, and (3) at P—T conditions sufficient to gener ate a thermal aureole within the pyroxene—hornfels facies. The rocks of the aureole show rheomorphic veining, and ana— texites which commonly exhibit flow layering or schlieren trending parallel to the immediate gabbro contact. Areas of more intense migma development were probably controlled by the distribution pattern of favourable.lithologies as modified by folding, faulting and emplacement characteristics of the massif. The coincidence of numerous geological contacts with lineaments is compatable with a magma cooling history involving doming and fissuring, with probable block subsidence, and the 'near—roof' level of Massif exposure.
AGE RELATIONSHIPS The volcanosedimentary assemblage was intruded by various bodies which are as follows (oldest first): — sill—like bodies of basics and ultrabasics, granitoids, dikes of diabase, and the Port Coldwell Alkali Massif. The diabase dikes are typical of those reported throughout the Superior Province and which have been dated at approximately 1700 m.y. The author originally thought the Port Coidwell Alkali Massif to have been intruded in the northwest by a younger granitoid, the so—called Little Pic River batholith (Puskas, 1964). But the observed field relations are better explained by assuming the formation of a palingenetic magma from an overlying granite. Minerals front the massif give ages of 1065 m.y. (K—Ar, Rb—Sr ages on biotites from nepheline syenites from Stop 5) and 1225 m.y. (Rb—Sr age on perthite from the laurvikite)(Fairbairn et al, 1959). In view of the widespread contamination of the magma further work is necessary. However, the massif is similar in age to the widespread Keweenawan intrusives of the Superior Basin (1000± myra) and may be from the same parental magma. ECONOMIC GEOLOGY The Port Coldwell Alkali Massif has been prospected for iron, base metals, radioactive minerals, nepheline, perthitic feldspar, and building stone. To date there has been no ore production. Iron The exposed gahbros along the periphery have been investigated for iron and base metals. The iron occurs as ilmenomagmetite—enriched layers or bodies, one inch to 70 feet wide, predominantly conformable to the layering of the adjacent gabbros. The high titanium content, 5 to 8 percent, and sub—marginal tonnages make the deposits uneconomic at this time. Base Metals Base metal investigations by various companies, including Moneta Porcupine; Lakehead,: Denison Mines, Keevil, Anaconda, and Conwest Exploration, have concentrated on the coarser grained, massive, gabbros (Inner Border zone 'A'). Stone Small scale quarrying of both 'red' and 'black', i.e. thirk varieties of laurvikite was begun in 1927 and continued into the l930's on a property located approximately 2 3/4 miles north of
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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
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-25-- ROOT SEVERANCE AND TECTONIC T
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-27- STRUCTURE OF ThE DULUTH GABBRO
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-29- 1. Department of Geology and G
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-31-. KEWEENANWAN COPPER DEPOSITS I
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—33- The youngest rocks in the ar
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-35- STRUCTURAL AN!) METAMORPHIC HI
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-37.- ARCHAEAN VOLCANIC STRATIGRAPH
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______ __________ _____ 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 and 80: —72 B— ABITIBI BELT —ø.jsour
Page 81 and 82: —74— Most of the metavolcanic
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: —87— Guide to the Port Coldwell
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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