Characterization of apatite within the Mactung W (Cu,Au) skarn deposit, Northwest Territories : implication for the evolution of skarn fluids

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dc.contributor.advisor Adlakha, Erin
dc.creator Roy-Garand, Andree
dc.date.accessioned 2019-12-02T15:10:03Z
dc.date.available 2019-12-02T15:10:03Z
dc.date.issued 2019
dc.identifier.uri http://library2.smu.ca/handle/01/29205
dc.description 1 online resource (89 pages) : illustrations (chiefly colour)
dc.description Includes abstract and appendices.
dc.description Includes bibliographical references (pages 78-80).
dc.description.abstract Skarn-hosted apatite from the Mactung deposit, Selwyn Basin, Northwest Territories, Canada, is characterized to understand the chemical evolution and signatures of mineralizing fluids. Petrography and rare earth element (REE) abundances constrain three generations of fluorapatite, each of which record distinct moments in the system&rsquo;s evolution. Type-i apatite occur with detrital phosphate nodules. This apatite contains variable &Sigma;REE+Y (1314 &plusmn; 821 ppm, 1&sigma;, n = 78) and show negatively sloping chondrite normalized REE+Y (REE+Y<sub>N</sub>) patterns with variable LREE<sub>N</sub>/HREE<sub>N</sub> (La<sub>N</sub>/Lu<sub>N</sub> = 27 &plusmn; 30) and weak Eu anomalies (Eu<sub>N</sub>/Eu<sub>N</sub>* = 0.6 &plusmn; 0.2; Eu* = &radic;Sm<sub>N</sub>*Gd<sub>N</sub>). The REE abundances of phosphate nodules from Mactung are similar to those reported in unmineralized units at Howards Pass in the Selwyn Basin. These REE patterns are similar to that of type-i apatite, suggesting that type-i apatite are recrystallization products of phosphate nodules, likely during isochemical contact metamorphism. Hydrothermal type-ii apatite occur with skarn assemblages and are divided into two sub-types: i) early type-ii apatite occur in prograde skarns and show high flat lying REE+Y<sub>N</sub> patterns (e.g., &Sigma;REE+Y = 17194 ppm, La<sub>N</sub>/Lu<sub>N</sub> = 3.5, n = 31 ) with negative Eu anomalies (e.g., Eu<sub>N</sub>/Eu<sub>N</sub>* = 0.1) and ii) later type-ii apatite occur in retrograde skarns and show bowl shaped to negatively sloped REE+Y<sub>N</sub> patterns, reflecting low MREE content (e.g. La<sub>N</sub>/Sm<sub>N</sub> = 10.2, Sm<sub>N</sub>/Lu<sub>N</sub> = 0.3, n = 17), and positive Eu anomalies (e.g., Eu<sub>N</sub>/Eu<sub>N</sub>* = 14.3). Type-iii apatite are associated with quartz-scheelite veins, which cross-cut prograde skarn. These apatite contain high &Sigma;REE+Y (7752 &plusmn; 496 ppm, n = 3) and exhibit bowl-shaped REE+Y<sub>N</sub> patterns, corresponding to low MREE (La<sub>N</sub>/Sm<sub>N</sub> = 8 &plusmn; 0.3), and no Eu anomaly. The REE patterns and paragenesis of hydrothermal apatite (i.e. type-ii and type-iii) indicate the presence of two chemically distinct ore fluids during the different stages of mineralization of the Mactung deposit. The first fluid is associated with prograde skarns and early type-ii apatite, whereas the second fluid, recorded in late type-ii and type-iii apatite, formed retrograde skarn and quartz veins. The REE+Y<sub>N</sub> patterns of late type-ii and type-iii apatite record a MREE fractionation through early crystallization of MREE-rich minerals. en_CA
dc.language.iso en en_CA
dc.publisher Halifax, N.S. : Saint Mary's University
dc.title Characterization of apatite within the Mactung W (Cu,Au) skarn deposit, Northwest Territories : implication for the evolution of skarn fluids en_CA
dc.type Text en_CA
thesis.degree.name Bachelor of Science (Honours Geology)
thesis.degree.level Undergraduate
thesis.degree.discipline Geology
thesis.degree.grantor Saint Mary's University (Halifax, N.S.)


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