A New 1:250K Scale Unified Legend for Precambrian
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eologic g a a l b s A new 1:250k scale unified legend o u t r i v n e a y m MGS for Precambrian rocks in Manitoba 1928 L. Chackowsky, T. Martins, M. Rinne, C. Couëslan and C. Böhm Manitoba Geological Survey Summary Figure 1: Previous 1:250k scale bedrock geology legend Figure 2: Revised 1:250k scale bedrock geology legend (draft) Intrusive Rocks Gabbro, diabase, diorite, norite Intrusive Rocks Volcanic Rocks & Derived Sediments Monzonite Proterozoic Phyllonite, mylonite, tectonite, cataclasite, Monzonite, monzogranite Diorite, quartz diorite, tonalite Arenites: quartz-plagioclase paragneiss, Proterozoic pB aZ1 pP schist pZ1 h) hornblende bearing monzonite to quartz aD h) diorite, quartz diorite, biote+hornblende- aS sandstone, biote gneiss, arkose The Manitoba Geological Survey (MGS) identified the Amphibolite pX Pegmate pBK mafic dikes (MacKenzie) uG Granite to granodiorite aV Undifferenated volcanic rocks aZ1h hornblende-bearing monzonite bearing Sedimentary Rocks pA m) mudstone, subordinate arenite q) quartz arenite, minor mudstone, monzonite to quartz g) garnet amphibolite P) megacrysc monzonite to monzogranite q) quartz diorite conglomerate Quartzite pXg granic pBL composionally layered uGl leucocrac monzonite h) amphibolite, diopside- &/or hornblende- x) biote gneiss with pyroxene pS Quartzo-feldspathic sandstone aV1 Felsic volcanic rocks bearing pQ Syenogranite, syenite Enderbite, enderbic gneiss need for a revised 1:250k scale bedrock geology legend pZ2 aE pXm mafic pBM mafic to ultramafic dikes uGN gneissic O) amphibolite with locally preserved pillow N) enderbic gneiss Tonalite to granodiorite, with tonalic to pSb biote-bearing (dominantly Molson) aV1P porphyric Felsic porphyric rocks (e.g. structures Quartz- to feldspar-porphyry g) enderbic gneiss, garnet bearing aT granodioric gneiss aR pBP porphyric hypabyssal) pR Monzodiorite to quartz monzonite S) schollen enderbite A) augen tonalite pSh hornblende-bearing pG Granite to granodiorite uT Granodiorite to tonalite aV1V volcaniclasc that is applicable to the entire province of Manitoba. Gabbro, diabase, diroite, norite pZ3 b) biote tonalite pB L) composionally layered gabbro Granite, leucocrac granite, quartz pSm magnete-bearing aT Granodiorite to tonalite Arenites: sandstone, siltstone, arkose, g) tonalic granofels pGb biote-bearing aG1 monzonite uB Gabbro, diabase, diroite, norite aV2 Intermediate volcanic rocks pS quartzofeldspathic paragneiss H) hybrid tonalite, tonalic gneiss pSq quartz sandstone Anorthosic gabbro, Metaconglomerate A) augen granite pGf fluorite-bearing pI aTf fluorite-bearing pC b) biote gneiss, meta-arkose h) hornblende tonalite anorthosite aV2V volcaniclasc h) hornblende bearing polymicc b) biote granite to granodiorite uU Ultramafic rocks h) hornblende bearing quartzofeldspathic L) tonalite to tonalic gneiss, layered Argillaceous sandstone to pGg garnet-bearing aTl leucocrac Most MGS field mapping programs are carried out at metaconglomerate Proterozoic and/or Archean h) hornblende-biote granite pW gneiss l) leucotonalite mudstone (e.g. turbidites) Ultramafic rocks N) gneissic metaconglomerate H) xenolith bearing granite, granodiorite pGh hornblende-bearing pU aV3 Mafic volcanic rocks aTo orthopyroxene-bearing m) magneferous quartzofeldspathic gneiss Amphibolite N) geneissic tonalite to tonalic gneiss Metamorphic Rocks Diorite, quartz diorite uA k) microcline granite tonalite (enderbite) M) quartzofeldspathic migmate and P) porphyric tonalite pC Conglomerate pGl leucocrac Metamorphic Rocks basalt and komaic pD m) magnete quartz diorite l) leucogranite aV3b scales of around 1:20k or 1:50k. In order to display this migmac gneiss x) hypersthene tonalite uY Metasedimentary rocks basalt aTH xenolith-bearing N) gneissic quartz diorite to granodiorite N) arkosic gneiss Gabbroic and mafic dykes (Molson N) gneissic granite to granodiorite gneiss pGo orthopyroxene-bearing Y) mylonic tonalite pCM monomicc (charnockite to opdalite) pY Metasedimentary rocks t) diorite to tonalite q) quartz arenite uB Swarm) P) porphyric and porphyroblasc granite aV3k komaite and komaic aTN gneissic x) pyroxene diorite X) pegmac granite, pegmate Ultramafic rocks pCP polymicc uA Amphibolite basalt type of information at 1:250k scale, unit shapes must be Tonalite to quartz diorite, granodiorite aU Conglomerate, volcanic derived (probably k) komaite, komaic basalt pA Amphibolite Enderbite pT A) augen tonalite Granodiorite, tonalite, quartz diorite pGH xenolith-bearing aD Diorite, quartz diorite uC Archean) aG2 s) ultramafic to mafic rocks, sapphirine aV3O pillow basalt pE x) gneissic ferrohypersthene enderbite b) biote tonalite A) augen granodiorite; felsic augen gneiss pF Iron formaon uN Felsic gneiss bearing pGN gneissic pAL layered amphibolite (quartz) diorite to simplified and assigned to regionally representative f) tonalite to granodiorite, fluorite-bearing b) biote granodiorite aV3P porphyric basalt aDg Granite, leucogranite Felsic volcanic rocks pFo oxide facies granodiorite Iron formaon H) hybrid tonalite, tonalic gneiss uG1 H) hybrid granodiorite to granic gneiss seriate or porphyric pF N) foliated granite, leucogranite aV1 F) volcanic fragmental rocks, related pGP Mylonite, tectonite, cataclaste aV3V volcaniclasc o) oxide facies iron formaon h) hornblende tonalite h) hornblende-bearing granodiorite pM sediments pFs silicate facies aDm magnete-bearing rock units. Using the previous 1:250k legend (Figure 1) s) silicate facies iron formaon l) leucotonalite, leucocrac gneissic tonalite l) leucogranodiorite pGX pegmac Granodioric gneiss to diatexite P) porphyric rhyolite Archean Intrusive Rocks N) gneissic granodiorite to gneissic tonalite, aDt diorite to tonalite Granite m) magnete tonalite to granodiorite uG2 Calc-silicate rock, marble, pN1 Felsic gneiss pG1 N) foliated granodioric gneiss locally migmac Y) mylonic volcanic rocks pK b) biote granite to granic gneiss N) gneissic to foliated tonalite to granodiorite dolomic marble pZ2 Syenite Sedimentary Rocks aX Pegmate aDx pyroxene-bearing g) gneissic garneferous tonalite-granodiorite P) porphyric, porphyroblasc, and Intermediate volcanic rocks for this purpose presented several problems. For f) granite, fluorite bearing Felsic to tonalic gneiss megacrysc granodiorite pN2 Intermediate gneiss aV2 pKx albite-pyroxene rock +/- quartz syenite Quartzo-feldspathic sandstone g) garneferous granite to granodiorite P) megacrysc biote tonalite to granodiorite uN A) augen gneiss pZ2q aS aXg granic ±garnet x) pyroxene granodiorite, gabbro marble aB Gabbro, diabase, diorite, norite H) hybrid granite b) biote ± hornblende gneiss x) clinopyroxene tonalite X) pegmate Mafic volcanic Rocks Monzodiorite to quartz pN3 Mafic gneiss aSb biote-bearing aXm mafic h) hornblende granite, aplite L) layered migmate gneiss, migmate aV3 pZ3 example, some unit names were not consistently Chloritoid schist F) mafic volcanic fragmental rocks, related pP Mudstone monzodiorite aBL composionally layered l) leucocrac granite Ultramafic rocks aH aSh hornblende-bearing pU Metasedimentary rocks sediments aG Granite to granodiorite aBP porphyric m) magnete granite, petmate uS O) pillowed basalt pZ3x pyroxene-bearing N) gneissic granite to granodiorite, granic monzodiorite aSm magnete-bearing applied throughout the province, and some names had Anorthosite, anorthosic gabbro P) mafic plagioclase-phyric flows Volcanic Rocks & Derived Sediments gneiss Undifferenated volcanic rocks aGb biote-bearing Anorthosic gabbro, Tonalite, tonalic gneiss aI Proterozoic / Archean aSq quartz sandstone aI P) porphyric and megacrysc granite, pV uT Volcaniclasc rocks and related pZ3M monzodiorite to quartz anorthosite aV4 pV Undifferenated volcanic rocks monzonite aGf fluorite-bearing leucogranite sedimentary rocks Sedimentary Rocks Argillaceous sandstone to connotations that were not appropriate for all regions in R) seriate to prophyric granite Rhyolite, dacite, pyroclasc rocks Migmate: mixture of granodiorite gneiss f) felsic volcaniclasc rocks aW aGg garnet-bearing Ultramafic rocks Ultramafic rocks, largely serpennized aM mudstone (e.g. turbidites) aU X) pegamc granite pV1 to tonalite gneiss, granite, tonalite i) intermediate volcaniclasc rocks pV1 Felsic volcanic rocks uC Conglomerate uU peridote pZ1 Monzonite aGh hornblende-bearing Metamorphic Rocks Granodiorite, granite, tonalite Granic and granodioric gneiss, Metagreywacke Argillaceous sandstone to aC Conglomerate which they occur. pG2 Intermediate volcanic rocks aW pV1P porphyric hornblende monzonite leucocrac b) biote granodiorite Mafic to ultramafic metavolcanic rocks aN1 migmate N) amphibolite-biote-garnet gneiss pZ1h uW aGl pV2 P) porphyric and aphyric basalt and to quartz monzonite mudstone Metasedimentary rocks H) hybrid granodiorite to granite gneiss uV3 T) tuffacious greywacke pV1V volcaniclasc aCM monomicc aY andesite D) laminated felsic gneiss aGo orthopyroxene-bearing h) hornblende granodiorite g) garneferous quartzofeldspathic gneiss Pegmate, aplite polymicc granodiorite l) leucocrac granodiorite Pillowed to massive mafic volcanic rocks Felsic porphyric rocks (e.g. Volcanic Rocks & Derived Sediments aCP Amphibolite pV3 X) felsic gneiss with abundant pegmate and aX pV2 Intermediate volcanic rocks pR aA N) gneissic granodiorite to tonalite k) basalt and komaic basalt aplite hypabyssal) aGH xenolith-bearing The revised 1:250k bedrock geology legend (Figure uV Undifferenated volcanic rocks P) porphyric and megacrysc granodiorite to O) pillow basalt aF Iron formaon aAL layered amphibolite Intermediate layered to migmac gneiss Quartz monzonite