Insights Into the Origin of the Scourie Dykes from Geochemistry and Geochronology

Insights Into the Origin of the Scourie Dykes from Geochemistry and Geochronology

Insights into the origin of the Scourie Dykes from geochemistry and geochronology by Joshua Davies $WKHVLVVXEPLWWHGLQSDUWLDOIXO¿OOPHQWRIWKHUHTXLUHPHQWVIRUWKHGHJUHHRI Doctor of Philosophy Department of Earth and Atmospheric Science University of Alberta © Joshua Davies, 2014 Abstract $PXOWLWHFKQLTXHJHRFKHPLFDOVWXG\RIWKH6FRXULHG\NHVLQWKH/HZLVLDQJQHLVV FRPSOH[ /*& RIQRUWKZHVW6FRWODQGLVSUHVHQWHG7KH6FRXULHG\NHVDUHDVHW RI QRUWKZHVWVRXWKHDVW WUHQGLQJ PD¿F DQG XOWUDPD¿F G\NHV WKDW LQWUXGH WKH /*& EHWZHHQWZRSHULRGVRIKLJKJUDGHUHJLRQDOPHWDPRUSKLVP1HZ83EUDGLRPHWULF DJHVIURP]LUFRQDQGEDGGHOH\LWHLQGLFDWHG\NHHPSODFHPHQWRFFXUUHGGXULQJWZR SHULRGVVHSDUDWHGE\aP\7KHPDMRULW\RIWKHG\NHVZHUHHPSODFHGDWa *DZLWKDPLQRULQWUXVLRQHYHQWDWa*D7KHGLVWULEXWLRQRIDJHVLQWKHa*D HYHQWLVFRQVLVWHQWZLWKG\NHHPSODFHPHQWGXULQJSRVWFROOLVLRQDOH[WHQVLRQDIWHUWKH FROOLVLRQRIWKH$VV\QWDQG5KLFRQLFKWHUUDQHVLQWKHQRUWKHUQ/*& 7KHR[\JHQLVRWRSLFFRPSRVLWLRQ į182 RI]LUFRQIURPWKH6FRXULHG\NHVLQGLFDWHV WKDWWKHVRXUFHUHJLRQRIWKHG\NHVFRQWDLQHGDORZį182FRPSRQHQW7KH]LUFRQV KDYHSULPDU\į182YDOXHVGRZQWR‰į182YDOXHVEHORZ‰ can only be FUHDWHGWKURXJKLQWHUDFWLRQZLWKPHWHRULFZDWHUDWWKH(DUWK¶VVXUIDFH7KHUHIRUH the Scourie dyke magmas likely contain a recycled component that has previously LQWHUDFWHGZLWKVXUIDFHZDWHUV7KHPDJPDWLFORZį18O signature in the zircons is ob- VFXUHGE\SRVWHPSODFHPHQWÀXLGDOWHUDWLRQGXULQJWKH&DOHGRQLDQRURJHQ\DWa 0D $ QHZ WHFKQLTXH LQYROYLQJ 5DPDQ VSHFWURVFRS\ DQG WUDFH HOHPHQW DQDO\VLV FRPELQHGZLWKLRQSUREHR[\JHQLVRWRSLFDQDO\VLVLVSUHVHQWHGZKLFKGLVWLQJXLVKHV DUHDVRI]LUFRQJUDLQVWKDWVWLOOUHFRUGSULPDU\į18O signatures from areas in grains ZKLFKKDYHEHHQUHVHW *HRFKHPLFDOPRGHOLQJRIWKH6FRXULHG\NHVLVDOVRSUHVHQWHG7KHPRGHOLQJLQ- dicates that melting of an enriched mantle source cannot produce the dyke trace HOHPHQWFKHPLVWU\0HOWLQJRID3ULPLWLYH0DQWOHVRXUFHIROORZHGE\DVVLPLODWLRQ ii of crustal material can explain the enriched trace-element compositions found in the G\NHV7KHJHRFKHPLFDOPRGHOLVFRQVLVWHQWZLWKWKHR[\JHQLVRWRSLFLQIRUPDWLRQ IURPWKH]LUFRQVLQWKHG\NHV An initial study investigating the possibility of oxygen isotopic analysis of baddeley- LWHE\LRQSUREHLVDOVRSUHVHQWHG,QPD¿FURFNVEDGGHOH\LWHLVPRUHFRPPRQWKDQ ]LUFRQDQGFRPPRQO\UHFRUGVFRQFRUGDQWRUFORVHWRFRQFRUGDQW83EDJHV2[\JHQ isotopic analysis of zircon has been instrumental in understanding U-Pb systematics DQGÀXLGURFNLQWHUDFWLRQV8QIRUWXQDWHO\EDGGHOH\LWHR[\JHQLVRWRSLFDQDO\VLVE\ ion probe is currently hindered by heterogeneous reference materials$QDO\VLVRI EDGGHOH\LWHIURPWKH'XFN/DNHVLOO '/6 LQQRUWKHUQ&DQDGDZKLFKKDVFRFU\V- WDOOL]HGZLWK]LUFRQVXJJHVWVWKDWWKHEDGGHOH\LWHFDQEHLQLVRWRSLFHTXLOLEULXPZLWK ]LUFRQDQGWKHUHIRUHUHFRUGWKHR[\JHQLVRWRSLFFRPSRVLWLRQRIWKHSDUHQWPDJPD 7KH'/6EDGGHOH\LWHR[\JHQLVRWRSLFFRPSRVLWLRQVDOVRLQGLFDWHWKDWEDGGHOH\LWH PD\H[FKDQJHR[\JHQPRUHUHDGLO\WKDQ]LUFRQZLWKPHWHRULFZDWHUZLWKRXWORVLQJ VLJQL¿FDQWOHDG iii Preface Some of the research conducted during this thesis forms part of an international and QDWLRQDOUHVHDUFKFROODERUDWLRQ7KHUHVXOWVSUHVHQWHGLQ&KDSWHUZHUHFROOHFWHGDW 0F(ZDQ8QLYHUVLW\8QLYHUVLW\RI:LVFRQVLQ0DGLVRQDQGWKH8QLYHUVLW\RI$O- EHUWD,FROOHFWHGWKH5DPDQGDWDZLWKWKHDVVLVWDQFHRI'U(ULQ:DOWRQDW0F(ZDQ 8QLYHUVLW\:KROHURFNODVHUÀXRULQDWLRQR[\JHQLVRWRSLFUHVXOWVZHUHJHQHUDWHGDW WKH8QLYHUVLW\RI:LVFRQVLQ0DGLGRQE\'U-RKQ9DOOH\'U5LFKDUG6WHUQZLWK assistance from me, conducted all SIMS oxygen isotopic results presented in chapter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