Prior to complete crystallization of leucogranitic magma at East Kemptville, tectonic fracturing induced a pressure drop, allowing a NaCl-HCl-HF-rich fluid phase to separate. This fluid caused pervasive sericitization and extracted the ore metals from the melt. It was then channeled into the fractures and caused greisenization in the apical part of the intrusion. During greisenization, the leucogranite was converted into quartz-sericite greisen through sequential replacement of K-feldspar and albite. Muscovite was replaced by topaz to form quartz-topaz greisen, host to sulphide and cassiterite mineralization. In this greisen, the OH$ sp-$ of muscovite is replaced by H$ sb2$O and O$ sp{2-},$ which leads to its dehydration during microprobe analyses. Close to veins, suphides and cassiterite were re-dissolved in quartz greisen. The altering fluid had a pH of 3.0 and contained 4.8m Cl, 3.7m Na, 0.53m Fe and minor F, K, S and Sn as determined from fluid inclusions and mineral equilibria. The temperature of greisenization was determined to be $480 pm 15 sp circ rm C$ using a F-OH exchange geothermometer between topaz and muscovite and oxygen isotopic data on cassiterite and quartz; the pressure was estimated to be 4.1 $ pm$ 1.0 kbars using fluid inclusion isochores. Alteration occurred though a process of compensated infiltration in which small aliquots of fluid were exchanged between the rock and the vein, while the bulk flow was parallel to the vein. This created a distribution of the components controlled by chemical potential gradients; Fe, Sn, S and F were transported away from the vein and Na towards it. Changes in physicochemical parameters of the fluid were quantified using computer simulation, which, in conjunction with fluid inclusion data, indicates that cassiterite precipitated in response to a pH increase. Changes in a$ sb{ rm Cl-}$ and $f rm O sb2$ were insufficient to account for cassiterite precipitation or acted against it. Modeling further showed that
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.42050 |
| Date | January 1996 |
| Creators | Halter, Werner E. |
| Contributors | Williams-Jones, Anthony E. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Earth and Planetary Sciences.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001564565, proquestno: NQ29955, Theses scanned by UMI/ProQuest. |
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