Program, Abstracts, and Guidebooks - University of Minnesota Duluth

More documents

Recommendations

Info

-7- KEWEENAWAN VOLCANIC GEOLOGY OF MICIIIPICOTEN ISLAND, LAKE SUPERIOR it. N. ANNELLS Postdoctorate Fellow Geological Survey of Canada, Ottawa ABSTRACT Recent re—mapping and petrographic examination by the author of the Keweenawan lava flows building Michipicoten Island shows that they form a highly differentiated 11,500—foot sequence of types ranging from coarse ophitic olivine—bearing basalts through olivine—free basalts and andesitic types to glassy porphyritic andesites and rhyolites. Some volcaniclastic horizons are intercalated in this south—dipping lava series and a few intercalations of conglomerate and sandstone outcrop at the west end of the island. The different- lava types are well intermixed and there is no obvious vertical gradation or cyclic distribution of lava types in the Michipicoten island succession. The lavas tend to occur in grouj,s of petrographically similar flows which can be traced as distinct strati— graphic units; an andesite group near the top of the succession can be followed across the entire island, a distance of 16 miles along strike. Near the median part of the succession the lavas show some lateral variation which may be the result of simultaneous extrusion of different flow types at the same general level from different vents. An agglomerate bearing large angular and rounded blocks of island lava types outcrops on the northwest shore of the island, and indicates proximity to an eruptive vent. The lower half of the exposed lava sequence is intruded at numerous different horizons by sheet—like or lentJ.cular bodies of pink acid quartz porphyry crowded with large phenocrysts of feldspar and quartz. These bodies are sometimes discordant to the lava flows and field evidence suggests that they are intrusions Basic intrusions are extremely rare on Michipicoten Island, only about six very thin basic inclined sheets being found on the entire shoreline. The varied basalt—andesite—rhycalite sequence and associated volcaniclastic rocks of Michipicoten Island are believed to have been erupted from a central volcano fed by a high level magma source. The presence of large volumes of acid material in the island sequence is a phenomenon' very similar to that seen in the Icelandic central volcanoes, which consist of highly diffentiated lavafvolcaniclastic edifices inter— finggred with widespread flood basalts and often intruded by acid material.
-8- SYNTHESIS OF EARLY PRECAMBRIAN STRATIGRAPHY NORTH OF LAKE SUPERIOR LORNE D. AYRES Ontario Department of Mines Toronto A section from Lake Superior Park to Geraldton, Ontario crosses three major, east-trending, Early Precambrian, lithologic and structural elements of the Superior Province of the Canadian Shield. From south to north these are the northern part of the Abitibi island arc, the Quetico sedimentary basin, and the southern part of the Keewatin island arc. Both the Abitibi and Keewatin arcs are formed from coalescing, subaqueous, basaltic shield volcanoes capped by subaerial to subaqueous, felsic to intermediate pyroclastic cones. Volcaniclastic greywacke sequences derived from felsic volcanism accumulated in intervolcano basins and partly overlap the felsic pyroclastic deposits. Small trondhjemite cratons within the island arcs were a local sOurce of sedimentary detritus. Although the island arcs have easterly trends, individual basins and volcanoes have diverse trends. Along the north edge of the Abitibi arc from Schreiber to Wawa, three isolated sedimentary formations were deposited in intervolcano basins, but they are all tongues of an extremely thick greywacke and siltstone formation deposited in the Quetico basin north of the arc. The formations become progressively younger from west to east. The sedimentary rocks of the Quetico basin, which are equivalent to the Couchiching Formation of western Ontario, overlie and intertongue with. the volcanic formations of the Abitibi arc and the source area was probably within the arc. Along the north edge of the basin, however, the sedimentary rocks underlie and intertongue with the volcanic formations of the Keewatin arc.! In this area, Keewatin volcanism is thus younger than Abitibi volcanism.
Page 1 and 2: -ç — — I: .t. F Geology Superi
Page 3 and 4: TABLE OF CONTENTS INSTITUTE DIRECTO
Page 5 and 6: -2- "P R 0 G R A M" Tate day, Ma9 5
Page 7 and 8: -4- SESSTOM 2 1.00 Business Meeting
Page 9: -6- F'viday, May Slit, 1970 Page No
Page 13 and 14: -10- THE SOUTHERN ASSOCIATED PART O
Page 15 and 16: -12- THE STRUCTURE OF THE NORTHERN
Page 17 and 18: -14- MT. ST. JOSEPH - AN ARC}IAEAN
Page 19 and 20: -16- A MODEL FOR TECTONIC VARIATION
Page 21 and 22: -18- EARLY PRECAMBRIAN GEOLOGY OF T
Page 23 and 24: DEFORMATION OF THE SEINE CONGLOMERA
Page 25 and 26: -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 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 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
show all

Program, Abstracts, and Guidebooks - University of Minnesota Duluth

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?