Petrographic Report on 10 Samples from the Jersey Mine Area, Kootenay Arc, British Columbia, Canada for Margaux Resources

Transcription

1 Report for: Linda Caron, M.Sc., P.Eng. VP Exploration Margaux Resources Sent to: Linda Caron, M.Sc., P.Eng. Report June 7, 2017 Peographic Report on 10 Samples from the Jersey Mine Area, Kootenay Arc, British Columbia, Canada for Margaux Resources Fabrizio Colombo, Ph.D., P.Geo.

2 Table of Contents 1. Inoduction Results Bibliography Peographic Descriptions...7 Sample 1: E m...7 Sample 2: E m...10 Sample 3: E m...13 Sample 4: E m...16 Sample 5: E m...19 Sample 6: E m...22 Sample 7: E m...24 Sample 8: E m...26 Sample 9: BiAu Zone Sample 10: BiAu Zone Selected SEM-EDS Speca

3 1. Inoduction Mrs. Linda Caron, VP Exploration of Margaux Resources submitted 10 rock samples to Vancouver Peographics for peographic analysis. The client indicated that the samples were collected from the Jersey Mine Area, Kootenay Arc, British Columbia, Canada. Mrs. Caron is interested in understanding the nature of the gold mineralization(s) in the area. The client provided geochemical data including gold and other ore metal content for the submitted samples. The attached Peographic Descriptions section provides the following for each sample: (i) the peographic rock classification; (ii) a brief microsuctural description; (iii) a table with the modal percentage and average grain size for each mineral; and (iv) a detailed description of the minerals in decreasing order of abundance. Samples 1 10 (see Table 1) were cut and prepared as ~20 40 mm polished thin sections (see the image of the billet on the first page of each description). The peographic classification follows the recommendations of Robertson (1999). The microsuctural terminology used in this report follows the recommendations and definitions of Vernon (2004), Passchier and Trouw (2005), and Ramdohr (1980). The magnetic susceptibility (see Table 1) was measured with a hand-held KT Magnetic Susceptibility Meter, and is intended to provide only an approximate estimate of the relative content of magnetic minerals within each sample. 2. Results The samples can be subdivided into 4 main suites. The first suite (Samples 1 3 and 10) consists of skarn of various compositions. In this suite, the rock type was assigned by listing the main minerals, in decreasing order of abundance, in front of the root name skarn. This suite is compositionally heterogeneous: the four samples are exemely different. Sample 1 hosts an essentially anhydrous assemblage of abundant plagioclase followed by garnet and epidote. Sample 2 is made up of prevailing epidote over amphibole. Sample 3 is again anhydrous, being formed by clinopyroxene, quartz, and garnet. Sample 10 is made up of amphibole, pyrrhotite, plagioclase, and epidote. The second suite (Sample 4) is a microleucogranite. This sample shows a medium-grained granular microsucture (microleucogranite 1) crosscut by a fine-grained microleucogranite (2) with a similar modal composition of K-feldspar, plagioclase, and quartz. The coarse-grained microleucogranite hosts a medium-grained xenoblastic crystal of garnet. SEM-EDS analysis 3

4 (see Photomicrograph 4c and Section 5) determined that the garnet is almandine. The third suite (Samples 5 8) is a metamorphic granofels. The plagioclase in these samples is xenoblastic, and I interpret it as the result of a metamorphic crystallization, which in Sample 8 was accompanied and overprinted by abundant vesuvianite. The original rock may still be considered as a metamorphosed dyke; however, the minerals contained within it were completely recrystallized or crystallized during a metamorphic episode. SEM-EDS analyses confirmed the nature of bismuth and bismuthinite (Sample 7). Tellurium occurs within the bismuth. The gold deposition can be atibuted to the bismuthrich deposition, which is associated with the carbonate±quartz infill episode. This infill episode is spatially associated with, and post-dates, the skarn event. The association of gold particles with the with the pyrite was confirmed by SEM-EDS analysis (Photomicrograph 8d, and Section 5). Gold particles were detected within the pyrite and in contact with the pyrrhotite (Sample 8, and Section 5). 4

5 Table 1: List of samples with their magnetic susceptibility and peographic classification. 1 The gold content listed in the last column was provided by the client. Sample No Magnetic Susceptibility (SI 10-3) E m E m E m E m E m E m E m E m BiAu Zone BiAu Zone Sample ID Rock classification after Robertson (1999). Rock Type Au ppm Plagioclase-garnet-epidote skarn Epidote-amphibole skarn; Bismuth-bismuthinite veinlets Clinopyroxene-quartz-garnet skarn Microleucogranite Plagioclase-white mica granofels Plagioclase-white mica-calcite granofels Plagioclase-white mica-calcite granofels Vesuvianite-calcite-plagioclase granofels Dolomite-sphalerite-pyrrhotite±bismuthinite zone(?) Amphibole-pyrrhotite-plagioclase-epidote skarn

6 3. Bibliography Deer WA, Howie RA, Zussmann J (1992) An inoduction to the rock-forming minerals. Longman, London Delvigne JE (1998) Atlas of micromorphology of mineral alteration and weathering. The Canadian Mineralogist, special publication 3. Mineralogical Association of Canada, Ottawa Passchier CW, Trouw RAJ (2005) Microtectonics (2nd edn). Springer, Heidelberg Ramdohr P (1980) The ore minerals and their intergrowths (2nd edn), vol 1/2. Pergamon Press, Oxford Robertson S (1999) Classification of metamorphic rocks. British Geological Survey Research Report RR 99/02, vol 2. Accessed May 2017 Tröger WE (1979) Optical determination of rock-forming minerals, part 1: determinative tables. Schweizerbart Science Publishers, Stuttgart Vernon RH (2004) A practical guide to rock microsucture. Cambridge University Press, Cambridge This report consists of 41 pages and is signed by F. Colombo, Ph.D., P.Geo. fab.peologic@gmail.com Tel: Web: 6

7 4. Peographic Descriptions Sample 1: E m Plagioclase-garnet-epidote skarn This sample shows a compositional layering defined by garnet-rich, plagioclase-epidote, and carbonate-rich zones. The garnet forms a massive aggregate in the upper part of the polished thin section and encloses finegrained crystals of epidote. The plagioclase and the epidote form a clustered xenoblastic aggregate, and the carbonate forms a foliated domain associated with very fine-grained unresolved minerals, probably clay. Mineral Alteration and Weathering Mineral Modal % Size Range (mm) Distinguishing Features plagioclase up to 0.5 low relief, first-order grey birefringence, albite twinning garnet up to 10 high relief, isoopic epidote up to 0.2 high relief, high birefringence, yellow to green pleochroism, heterogeneous disibution of the birefringence colours dolomite (and calcite?) up to 0.1 high relief, exeme birefringence, slow reaction to cold dilute (10%) HCl 1 2 up to 0.2 low relief, low birefringence (up to first-order grey) 1 2 up to 0.01 earthy unresolved K-feldspar clay(?) arsenopyrite up to 0.1 high reflectance, white, anisoopic pyrite up to 0.1 high reflectance, creamy white, isoopic up to 0.05 moderate relief, birefringence up to third-order blue white mica Garnet is xenoblastic and forms massive aggregates (up to 10 mm thick) in the upper part of the polished thin section. The garnet hosts fine-grained xenoblastic inclusions of epidote and very fine-grained aggregates of probable clay after plagioclase(?). The garnet is crosscut by 7

8 fractures and carbonate-bearing veinlets. Plagioclase prevails over the epidote in the middle zone of the polished thin section (see white zone in the image above). The plagioclase is xenoblastic and shows complex twinning. The plagioclase is intergrown with subordinate fine-grained crystals of epidote. In some cases, the plagioclase is intergrown with subordinate K-feldspar. Epidote is xenoblastic. It is subordinate to the plagioclase and the garnet in two of the three zones distinguished in this polished thin section. The epidote crystals tend to form clusters parallel with the layering in the plagioclase-epidote zone. Carbonate is concenated within the lower part of the polished thin section. The slow reaction to cold dilute (10%) HCl indicates the prevalence of dolomite. However, small pockets of briskly reacting (calcite) carbonate are dispersed within this zone, in which a clustering is defined by very fine-grained aggregates of unresolved minerals. Xenoblastic pseudomorphs (up to 0.5 mm long) made up of very fine-grained white mica are dispersed within the carbonate. Fine-grained idioblastic crystals of arsenopyrite and subordinate crystals of pyrite are dispersed within the carbonates in the lower part of the polished thin section (Photomicrograph 1c). The sulphides are spatially associated with the clusters of unresolved material. Photomicrograph 1a: Clustering of earthy unresolved minerals (clay?) within the carbonate-rich zone. Planepolarized ansmitted light. Photomicrograph 1b: The plagioclase-epidote zone consists of a granoblastic aggregates of coarsergrained plagioclase (pl) and subordinate finer-grained epidote (ep). Plane-polarized ansmitted light. 8

9 Photomicrograph 1c: Irregular clusters of fine-grained arsenopyrite (ap) and pyrite are dispersed within the carbonate-rich zone. Plane-polarized reflected light. 9

10 Sample 2: E m Epidote-amphibole skarn Bismuth-bismuthinite veinlets This sample is dominated by an inequigranular xenoblastic aggregate of epidote, subordinate and heterogeneously dispersed amphibole, interstitial quartz, and calcite. In the upper left corner of the polished thin section, an inequigranular granoblastic aggregate of calcite and lesser dolomite(?) occurs. Finely intergrown bismuth-bismuthinite filled in a thin veinlet crosscutting the xenoblastic microsucture and forms irregular clusters dispersed within the epidote-rich aggregate. Mineral Modal % Size Range (mm) Distinguishing Features epidote up to 1 high relief, high birefringence, yellow to green pleochroism, heterogeneous disibution of the birefringence colours amphibole up to 1 long moderate relief, song pleochroism with green to brown tints, extinction angles up to 18 calcite and dolomite 7 9 up to 2 high relief, exeme birefringence, brisk and slow reaction to cold dilute (10%) HCl quartz 5 6 up to 1 low relief, birefringence up to first-order white bismuthinite 0.5 up to 0.15 moderately to highly reflectant, soft, anisoopic, white bismuth 0.4 up to 0.2 highly reflectant, soft, anisoopic, creamy white mineral X up to 0.03 moderately reflectant, songly bireflectant scheelite up to 0.25 moderate to high relief, highly birefringent, fluorescent in shortwave ulaviolet light Inequigranular xenoblastic crystals of epidote dominate the composition of this polished thin section. Their grain size ranges from 0.1 mm up to 1 mm. The epidote is intergrown with interstitial quartz and heterogeneously disibuted xenoblasts of amphibole. Amphibole is inequigranular (up to 0.5 mm long) and xenoblastic, and it is heterogeneously 10

11 dispersed within the epidote-rich aggregate. The amphibole shows song pleochroism with brown tints and extinction angles up to 18. Quartz forms interstitial crystals intergrown with the epidote and the amphibole. The coarsest crystals and veinlet-like aggregates are spatially associated with the bismuth-rich veinlets. Calcite forms interstitial and xenoblastic crystals of up to 2 mm. Dolomite is concenated in the upper left part of the polished thin section. In this domain, the dolomite is associated with finer-grained crystals of calcite, which are distinguished by their brisk reaction to cold dilute (10%) HCl. The calcite, similarly with the quartz, shows coarser grains and is spatially associated with the bismuth-rich veinlets (Photomicrograph 2c). Bismuth shows high reflectance and a white creamy colour in plane-polarized reflected light (Photomicrograph 2c and 2d). The bismuth is intergrown with less reflectant, anisoopic crystals of bismuthinite (Photomicrographs 2c and 2d). A less reflectant, light-brown mineral (mineral X) is intergrown with the bismuth-rich minerals and is unresolved under planepolarized reflected light (Photomicrograph 2d). Two xenoblastic crystals of scheelite (up to 0.25 mm) are intergrown with the epidote, the quartz, and the subordinate amphibole in one case, and with the bismuth in the other. The scheelite is fluorescent when lit by short-wave ulaviolet light. Photomicrograph 2a: Elongate crystal of amphibole (am) is intergrown with abundant epidote (ep) interstitial calcite. Plane-polarized ansmitted light. Photomicrograph 2b: In most cases, the bismuth and bismuthinite form irregular clusters dispersed within the epidote-rich aggregate. Plane-polarized reflected light. 11

12 Photomicrograph 2c: In one case, the bismuth (creamy white) and the bismuthinite (light blue) are concenated within an irregular veinlet. Planepolarized reflected light. Photomicrograph 2d: The difference in colour between the two bismuth-bearing minerals is more evident at higher magnification. A less reflectant unresolved mineral occurs along some of the boundaries between the bismuth (white) and bismuthinite (light blue). Plane-polarized reflected light. 12

13 Sample 3: E m Clinopyroxene-quartz-garnet skarn This polished thin section is made up of two main domains. In the upper part, Domain A is made up of an inequigranular xenoblastic aggregate of clinopyroxene (diopside?), quartz, calcite, amphibole, garnet, epidote, and sphalerite. In the lower part (Domain B), an irregular band of garnet and xenoblastic clinopyroxene dominates the composition. Mineral Modal % Size Range (mm) Distinguishing Features clinopyroxene up to 1 two cleavage systems oriented at 90, high relief, birefringence up to the second order quartz 8 10 up to 2.5 low relief, birefringence up to first-order white calcite 7 9 up to 3 high relief, exeme birefringence, brisk reaction to cold dilute (10%) HCl amphibole 2 3 up to 0.5 long moderate relief, moderate pleochroism with green tints; extinction angles up to up to 1 high relief, high birefringence, yellow to green pleochroism, heterogeneous disibution of the birefringence colours hydrogrossular 1 2 up to 1 high relief, isoopic; in some cases anisoopic sphalerite 0.1 clusters up to 3.5 long low reflectance, grey, isoopic scheelite up to 0.2 high relief, highly birefringent, fluorescent in short-wave ulaviolet light chalcopyrite up to 0.02 high reflectance, yellow Domain A (~60% of PTS) epidote Domain B (~30% of PTS) clinopyroxene up to 1 two cleavage systems oriented at 90, high relief, birefringence up to the second order garnet 5 10 massive band 2 20 mm high relief, isoopic; in some cases anisoopic 13

14 Mineral epidote scheelite Modal % Size Range (mm) Distinguishing Features 2 4 up to 0.2 high relief, high birefringence, yellow to green pleochroism, heterogeneous disibution of the birefringence colours up to 0.2 high relief, highly birefringent, fluorescent in short-wave ulaviolet light Clinopyroxene prevails in Domain A as xenoblastic inequigranular crystals (up to 1.2 mm long). Its nature is distinguished by the occurrence of perfect cleavages and in the same crystals oblique extinction up to 40. In Domain A, the clinopyroxene is overprinted by subordinate amphibole and is intergrown with subordinate quartz, calcite, garnet, and epidote (Photomicrograph 3a). In Domain B, the clinopyroxene is associated and in some cases hosted as inclusions within a band of garnet and sparsely disibuted epidote. Quartz forms xenoblastic patches (up to 2.5 mm), which are heterogeneously dispersed in Domain A and are spatially associated with increased amounts of epidote. Calcite is xenoblastic and reaches 3 mm in size. Similarly with the quartz, it is heterogeneously dispersed within Domain A. Garnet is dispersed within Domain A as xenoblastic fine- to medium-grained crystals, and as an elongate band within Domain B. In some cases, the garnet shows birefringent zones indicating it is a hydrogrossular. Amphibole is xenoblastic and overprinted the clinopyroxene in Domain A. Its deep green to brown colour and distinct pleochroism suggest its composition is actinolitic. Sphalerite forms irregular clusters, which define a discontinuous veinlet within Domain A. The sphalerite hosts very fine-grained dispersions or exsolution droplets of chalcopyrite. Rare xenoblastic crystals of scheelite (up to 0.2 mm) are dispersed within the xenoblastic aggregate of epidote. 14

15 Photomicrograph 3a: Xenoblastic clinopyroxene (cpx) is intergrown with subordinate quartz, (qz) carbonate (cb), garnet, and actinolite (green) in Domain A. Planepolarized ansmitted light. Photomicrograph 3b: An elongate band of garnet (isoopic) is associated with and hosts xenoblastic clinopyroxene (highly birefringent) in Domain B. Crossed Nicols ansmitted light. Photomicrograph 3c: Xenoblastic quartz (white) is interstitial with respect to xenoblastic to subidioblastic clinopyroxene and subordinate epidote. Crossed Nicols ansmitted light. Photomicrograph 3d: Rare crystals of scheelite (sc) are dispersed within the epidote and the clinopyroxene. Crossed Nicols ansmitted light. 15

16 Sample 4: E m Microleucogranite This polished thin section consists of medium-grained (up to 0.8 mm) granular microsucture (Photomicrograph 4a) and a fine-grained (up to 0.3 mm) granular microsucture (Photomicrograph 4b) defined by K-feldspar, plagioclase, and quartz. In the image of the billet above, the finer-grained part of the granitic rock occupies the entire lower part of the billet, while in the polished thin section it defines a ~6 mm thick vein-like domain indicating that the finer-grained granitoid post-dated the coarser-grained granitoid. Mineral Alteration and Weathering Mineral Modal % Size Range (mm) Distinguishing Features K-feldspar low relief, low birefringence (up to first-order grey) plagioclase (albite) low relief, first-order grey birefringence, albite twinning quartz low relief, birefringence up to first-order white up to 0.6 long wm: moderate relief, birefringence up to third-order blue, saight extinction garnet 0.25 high relief, isoopic scheelite up to 0.2 high relief, highly birefringent, fluorescent in short-wave ulaviolet light pyrite up to 0.1 high reflectance, creamy white, isoopic [biotite?] white mica and clay K-feldspar prevails slightly over the plagioclase in the two granitoids and defines an inequigranular anhedral aggregate. In some cases, the K-feldspar is perthitic and is subtly altered by a very fine-grained dispersion of very fine-grained unresolved material. The earthy dispersions are more abundant in the finer-grained part of the microleucogranite. Plagioclase forms anhedral crystals, which are subordinate to the K-feldspar and are characterized by albite twinning and refractive indexes lower than those of the quartz. Its composition is albitic. Quartz forms fine-grained anhedral to interstitial crystals associated and intergrown with the feldspars. No differences in composition are detected between the two portions of the granite 16

17 The rare subhedral crystals of biotite are completely replaced by epitaxial white mica (only in the coarser-grained microgranite) and clay. The very low amount of ferromagnesian minerals, assuming the pseudomorphic aggregate of white mica and clay as one of them, indicate a very low colour index; therefore, the microgranites are both leucocratic. One anhedral (or xenoblastic?) crystal of garnet (~0.25 mm). The SEM-EDS analysis of the garnet (see Section 5, Specum 2.10) contains Si, Al, Mn, Fe, and subordinate Ca, thus indicating it is almandine/spessartine. The Ca-poor composition of the garnet and its occurrence within the coarser microleucogranite (Photomicrograph 4c) suggest that this apparently preserved magmatic rock predated the skarn event. Very rare pyrite crystals (up to 0.1 mm) are dispersed within the finer-grained microleucogranite and very fine-grained pyrite and/or pyrrhotite overprinted some of the pseudomorphs after biotite. Photomicrograph 4a: A granular anhedral microsucture is defined by K-feldspar (kf), plagioclase (pl), and quartz(qz). Crossed Nicols ansmitted light. Photomicrograph 4b: The same constituents shown in Photomicrograph 4a define a finer-grained granular microsucture that forms a vein-like domain within the polished thin section. Crossed Nicols ansmitted light. 17

18 Photomicrograph 4c: An anhedral crystal of garnet occurs within the medium-grained microleucogranite. Plane-polarized ansmitted light. 18

19 Sample 5: E m Plagioclase-white mica granofels Relicts of medium-grained granular microsucture defined by plagioclase occur within a moderately to songly altered aggregate of white mica. The songly altered polished thin section is crosscut by a ~2 mm thick quartz-albite vein and thinner carbonate veinlets. Mineral Alteration and Weathering Mineral Modal % Size Range (mm) Distinguishing Features alteration zone (~89% of PTS) plagioclase (albite?) up to 1 low relief, first-order grey birefringence, albite twinning white mica up to 0.5 moderate relief, birefringence up to third-order blue, saight extinction quartz up to 0.2; rare up to 0.4 low relief, birefringence up to first-order white carbonate 1 up to 0.05 high relief, exeme birefringence, slow reaction to cold dilute (10%) HCl rutile up to 0.3 long high relief, brown under planepolarized light, anisoopic quartz-white mica-albite vein (~10% of PTS) quartz 9 10 low relief, birefringence up to first-order white albite low relief, first-order grey birefringence, albite twinning white mica scheelite carbonate veinlets (~1% 19 moderate relief, birefringence up to third-order blue, saight extinction up to 0.5 high relief, highly birefringent, fluorescent in short-wave ulaviolet light

20 Mineral Alteration and Weathering Mineral Modal % Size Range (mm) Distinguishing Features of PTS) dolomite(?) 1 high relief, exeme birefringence, slow reaction to cold dilute (10%) HCl white mica moderate relief, birefringence up to third-order blue, saight extinction White mica songly altered the host rock and forms very fine- to fine-grained flakes randomly oriented within the polished thin section. White mica crystals form radial aggregates within the host rock and within the quartz vein and carbonate veinlets, indicating that its crystallization continued throughout the alteration of the host rock and the infill stages. Albite forms anhedral crystals (up to 1 mm) defining medium-grained relict microsuctures. It must be noted that the granular microsucture includes quartz only in some portions of the host rock (Photomicrograph 5b). The song alteration may have completely changed the primary microsucture, assuming that this dyke had a microsucture similar to Sample 4. Albite crystals are distinguished by their albite twinning. Some subhedral crystals of albite are dispersed along the quartz vein walls (Photomicrograph 5a), indicating a high temperature during the infill stage. Rare flakes of white mica and rare crystals of scheelite (Photomicrograph 5d) are associated within the vein with the quartz and the albite. Quartz is concenated within a ~2mm thick vein (Photomicrograph 5a). Fine-grained quartz crystals are heterogeneously dispersed within the host rock as a consequence of the infill episode. Carbonate is concenated within irregular, discontinuous veinlets within the host rock. The slow reaction to cold dilute (10%) HCl suggests that most of the carbonate is dolomite. 20

21 Photomicrograph 5a: Quartz (qz) dominates the composition of the vein. Subhedral crystals of albite (ab) and rare white mica are dispersed along the vein walls. Crossed Nicols ansmitted light. Photomicrograph 5b: In the host rock, some areas show a partially preserved granular microsucture (left of photomicrograph). On the right, the rock is songly altered by white mica and carbonate. Crossed Nicols ansmitted light. Photomicrograph 5c: Veinlets of carbonate and rare white mica crosscut the songly altered granular microsucture. Crossed Nicols ansmitted light. Photomicrograph 5d: Rare medium-grained crystals of scheelite (sc) occur along the quartz-rich vein walls. Plane-polarized ansmitted light. 21

22 Sample 6: E m Plagioclase-white mica-calcite granofels A medium-grained granular microsucture is defined by heterogeneously dispersed plagioclase (white in the billet) and rare quartz, and are overprinted by inequigranular flakes of white mica (grey in the billet), calcite, and irregular clusters of molybdenite, bismuthinite(?), and bismuth. Mineral Modal % Size Range (mm) Distinguishing Features plagioclase up to 1 low relief, first-order grey birefringence, albite twinning white mica moderate relief, birefringence up to third-order blue, saight extinction calcite 5 7 up to 2.5 high relief, exeme birefringence, brisk reaction to cold dilute (10%) HCl quartz 2 3 up to 0.25 low relief, birefringence up to first-order white molybdenite 0.2 up to 0.7 low reflectance, pleochroic (blue to grey tints), soft bismuthinite 0.1 up to 0.4 moderately to highly reflectant, soft, anisoopic, white bismuth up to 0.15 highly reflectant, soft, anisoopic, creamy white pyrrhotite(?) up to 0.2 high reflectance, light brown, anisoopic Plagioclase is medium grained (up to 1 mm long) and anhedral and defines a granular microsucture. The plagioclase is weakly altered by a very fine-grained dispersion of carbonate and is heterogeneously overprinted by fine-grained flakes of white mica. In most crystals of plagioclase, albite twinning is distinguished. White mica forms fine-grained and in some cases up to 1.2 mm long flakes. The white mica is randomly oriented and in some cases forms radial aggregates, indicating that its crystallization occurred in the absence of sain. The white mica, the carbonate, and the sulphide-rich clusters heterogeneously overprinted the granular microsucture. Quartz is rare and forms fine- to medium-grained interstitial crystals intergrown with the plagioclase. 22

23 Calcite forms xenoblastic crystals of up to 2.5 mm heterogeneously dispersed within the granofels. Molybdenite is medium grained and xenoblastic (Photomicrograph 6b). It is dispersed in an irregular cluster associated with xenoblastic bismuthinite, as well as subordinate bismuth (Photomicrograph 6b) and probable pyrrhotite(?). Photomicrograph 6a: Anhedral plagioclase (pl) defines a granular microsucture and is overprinted by fine- to medium-grained white mica (wm). Crossed Nicols ansmitted light. Photomicrograph 6b: Xenoblastic molybdenite is deformed and intergrown with xenoblastic bismuthinite (white) and rare bismuth (white arrow). Plane-polarized reflected light. Photomicrograph 6c: The pseudolamellar crystals of molybdenite (bluish grey) are finely intergrown with bismuthinite (white). Plane-polarized reflected light. 23

24 Sample 7: E m Plagioclase-white mica-calcite granofels This polished thin section is similar to Sample 7. Anhedral crystals of plagioclase define a granular microsucture, which is overprinted by white mica, carbonate, quartz, and clusters of bismuthinite and lesser bismuth. No molybdenite occurs in this sample, and the calcite and the quartz define an infill-like domain spatially associated with the bismuth-rich minerals. Mineral Modal % Size Range (mm) Distinguishing Features plagioclase up to 0.8 low relief, first-order grey birefringence, albite twinning white mica up to 1.2 moderate relief, birefringence up to third-order blue, saight extinction calcite up to 1.5 high relief, exeme birefringence, brisk reaction to cold dilute (10%) HCl quartz up to 1.5 low relief, birefringence up to first-order white up to 3.9 long moderately to highly reflectant, soft, anisoopic, white up to 0.1 highly reflectant, soft, anisoopic, creamy white bismuthinite 1 2 bismuth gold song reflectance, yellow, soft Plagioclase forms anhedral crystals of up to 0.8 mm. The plagioclase hosts very fine-grained dispersions of probable calcite and shows albite twinning. The plagioclase-rich aggregate is overprinted by the white mica and the carbonate and later crosscut by the calcite-quartz infilllike domains. White mica forms fine- to medium-grained randomly oriented flakes and some radial aggregates. The white mica prevails over the fine- to medium-grained calcite, which occurs dispersed within the host rock and tends to form irregular, discontinuous infill-like domains. Quartz is concenated into some irregular infill-like domains crosscutting the granofels. One of these quartz-rich domains (see lower part of the billet in the image above, and also Photomicrograph 7b) hosts the coarse-grained crystal of bismuthinite (up to 3.9 mm long). The bismuthinite hosts subordinate crystals of bismuth (Photomicrograph 7c). The 24

25 bismuthinite and the white mica are finely intergrown around the coarse-grained crystal of bismuthinite, thus indicating that these two minerals likely crystallized together. Photomicrograph 7a: The granular aggregate of plagioclase (pl) is overprinted by white mica (wm). Crossed Nicols ansmitted light. Photomicrograph 7b: A deformed xenoblastic crystal of bismuthinite is intergrown with quartz and white mica (wm). The area in the white box is detailed in Photomicrograph 7d. Plane-polarized reflected light. Photomicrograph 7c: The anisoopic crystal of bismuthinite is fractured and hosts irregularly shaped crystals of bismuth (blue arrows). Plane-polarized reflected light. Photomicrograph 7c: Same area as shown in the white box in Photomicrograph 7b. A particle of gold (blue arrow) deposited in the crack of the bismuthinite crystal. Plane-polarized reflected light. 25

26 Sample 8: E m Vesuvianite-calcite-plagioclase granofels Xenoblastic patches of vesuvianite (see brown patches on the image of the billet above) overprinted a granular aggregate of plagioclase, calcite, and quartz. The sample is crosscut by intersecting veinlets of calcite. The sample shows a compositional heterogeneity, with fine-grained plagioclase overprinted by medium- to coarsegrained vesuvianite. Mineral Modal % Size Range (mm) Distinguishing Features vesuvianite massive high relief, low birefringence calcite up to 1.5 high relief, exeme birefringence, brisk reaction to cold dilute (10%) HCl plagioclase up to 1.5 low relief, first-order grey birefringence, albite twinning white mica 2 4 up to 0.02 moderate relief, birefringence up to third-order blue, saight extinction pyrite 0.2 up to 0.13 high reflectance, creamy white, isoopic pyrrhotite 0.1 up to 0.1 high reflectance, light brown, anisoopic bismuth 0.05 up to 0.6 highly reflectant, soft, anisoopic, creamy white bismuthinite up to 0.1 moderately to highly reflectant, soft, anisoopic, white gold up to 0.17 long song reflectance, yellow, soft Vesuvianite forms xenoblastic crystals intergrown with very fine- to medium-grained crystals of calcite, and medium-grained xenoblastic plagioclase (Photomicrographs 8a and 8b). The vesuvianite shows low birefringence, and shows high relief in ansmitted light. The vesuvianite is fractured and crosscut by calcite-rich veinlets. Calcite forms medium-grained interstitial crystals intergrown with the vesuvianite, plagioclase, and subordinate quartz. The calcite forms very fine-grained crystal aggregates, which in some cases are associated with very fine-grained flakes of white mica, sulphides, and gold. 26

27 Plagioclase is xenoblastic, and it is intergrown with the more abundant vesuvianite. In some cases, the plagioclase and the vesuvianite share saight boundaries, indicating that their crystallization occurred at the equilibrium for the two minerals (e.g., Photomicrographs 8a and 8b). Most of the plagioclase crystals show albite twinning and are relatively fresh. I tentatively interpret this plagioclase and the plagioclase in the other granofels as a metamorphic product and not as a magmatic relict. Pyrite and subordinate pyrrhotite (Photomicrographs 8c and 8d) form irregular clusters dispersed in the lower part of the polished thin section (i.e., the vesuvianite-free part) and rarely within the cracks of the vesuvianite. Very fine-grained particles of gold (Photomicrograph 8d) are dispersed within the idioblastic pyrite. Other gold particles are dispersed within probable bismuthinite (Photomicrograph 8e), within the calcite hosting the bismuthinite (Photomicrograph 8f), and are also intergrown with an amoeboid crystal of bismuth (Photomicrograph 8g). Photomicrograph 8a: Xenoblastic vesuvianite (ve) is intergrown with subordinate plagioclase (pl). Planepolarized ansmitted light. Photomicrograph 8b: Same area as shown in Photomicrograph 8a. The vesuvianite shows low birefringence and hosts unresolved mineral inclusions. Plane-polarized ansmitted light. 27

28 Photomicrograph 8c: Irregular clusters of idioblastic pyrite (white) and xenoblastic pyrrhotite (light brown) are dispersed within patches of calcite. Plane-polarized reflected light. Photomicrograph 8d: Detail of the pyrite aggregate shown in Photomicrograph 8c. Very fine-grained particles of gold (blue arrow) are hosted within an idioblastic crystal of pyrite. Plane-polarized reflected light. Photomicrograph 8e: Gold particles (yellow) are dispersed within a probable aggregate of bismuthinite. Plane-polarized reflected light. Photomicrograph 8f: A particle of gold (yellow) is hosted within bismuthinite (light blue) and bismuth (white) within crystals of calcite (ca). Plane-polarized reflected light. 28

29 Photomicrograph 8g: A gold particle (yellow) (up to 0.17 mm long) is intergrown with an amoeboid crystal of bismuth. Other smaller gold particles (white arrows) are hosted together with the bismuth within an aggregate of calcite (ca). Plane-polarized ansmitted light. 29

30 Sample 9: BiAu Zone 1 Dolomite-sphalerite-pyrrhotite±bismuthinite zone A compositional layering is defined by irregular domains of sphalerite and pyrrhotite alternated within a fine-grained aggregate of dolomite (Photomicrographs 9a and 9b). Mineral Modal % Size Range (mm) dolomite up to 0.5 long high relief, exeme birefringence, slow reaction to cold dilute (10%) HCl sphalerite up to 1.2 long low reflectance, grey, isoopic pyrrhotite up to 1.2 long high reflectance, light brown, anisoopic up to 0.15 moderately to highly reflectant, soft, anisoopic, white bismuthinite Distinguishing Features Fine-grained crystals of dolomite prevail over the sulphides (Photomicrograph 9a) and show a preferred dimensional orientation, which defines a foliation within this sample. The dolomite is distinguished by its slow reaction to cold dilute (10%) HCl. The dolomite hosts irregular domains and folded beds of sphalerite (Photomicrograph 9a), sphalerite-pyrrhotite (Photomicrograph 9b), and sphalerite-pyrrhotite-bismuthinite (Photomicrograph 9c). Sphalerite forms medium-grained crystals showing a preferred dimensional orientation parallel to the foliation defined by the dolomite. In some cases, the sphalerite is inclusion-free (Photomicrograph 9a); in most cases the sphalerite is intergrown with subordinate pyrrhotite and lesser bismuthinite. Pyrrhotite forms xenoblastic crystals hosted within the sphalerite. The pyrrhotite is fresh and is slightly fractured. Bismuthinite is subordinate to the sphalerite and the pyrrhotite and forms amoeboid to xenoblastic crystals spatially associated with the pyrrhotite (Photomicrograph 9c). 30

31 Photomicrograph 9a: A layer of sphalerite (opaque) is oriented parallel to the foliation defined by the preferential iso-orientation of the fine-grained crystals of dolomite. Crossed Nicols ansmitted light. Photomicrograph 9b: Within the sphalerite (grey) xenoblastic pyrrhotite (light brown) is dispersed. Planepolarized reflected light. Photomicrograph 9c: In some cases, the xenoblastic pyrrhotite is intergrown with xenoblastic to amoeboid bismuthinite (light blue). Plane-polarized reflected light. 31

32 Sample 10: BiAu Zone 2 Amphibole-pyrrhotite-plagioclase-epidote skarn This heterogeneous sample is made up of medium-grained xenoblastic aggregates of amphibole (dark green on the billet; see image above), massive domains of pyrrhotite, moderately altered plagioclase (white), and epidote. Mineral Alteration and Weathering Mineral pyrrhotite amphibole plagioclase epidote Fe-chlorite Modal % Size Range (mm) Distinguishing Features massive high reflectance, light brown, anisoopic moderate relief, moderate pleochroism (X: light green; Y: light yellow green; Z: light bluish green); extinction angle up to epidote and/or clay(?) up to 2.5 long low relief, first-order grey birefringence, rare albite twinning 5 7 up to 1.7 long high relief, high birefringence, yellow to green pleochroism, heterogeneous disibution of the birefringence colours up to 0.5 long moderate relief, weak pleochroism with green tints, saight extinction, low anomalous birefringence, positive elongation pyrite up to 0.1 high reflectance, creamy white, isoopic K-feldspar up to 0.1 low relief, low birefringence (up to first-order grey) Amphibole is medium grained and xenoblastic, and its crystals are randomly oriented within irregular domains hosting heterogeneously dispersed domains of pyrrhotite, plagioclase, and epidote. The amphibole shows song pleochroism with green to brown tints (X: light green; Y: light yellow green; Z: light bluish green), and extinction angles up to 15. These optical features suggest that the amphibole is actinolite. Irregular aggregates of randomly oriented lamellae of Fe-chlorite form clusters within the amphibole-rich domains. Pyrrhotite is concenated into two main massive and roughly sub-parallel domains (up to 5 mm thick) and medium-grained amoeboid crystals intergrown with amphibole, plagioclase, 32

33 and epidote in between the two massive domains. The pyrrhotite is weakly fractured and unaltered in this polished thin section. Very rare xenoblastic crystals of pyrite are dispersed within the massive pyrrhotite. Plagioclase forms medium-grained xenoblasts, which are concenated around the massive domains of pyrrhotite. The plagioclase is moderately altered by a very fine-grained dispersion of earthy unresolved material (clay and/or epidote), which impart to the plagioclase the white colour visible on the billet. Very rare fine-grained fragments of K-feldspar are distinguished by their typical yellow stain on the billet. Medium-grained xenoblastic crystals of epidote form irregular clusters dispersed within the polished thin section and spatially associated with the massive to amoeboid pyrrhotite. Photomicrograph 10a: A cluster of epidote (ep) and a xenoblastic aggregate of amphibole (am) host amoeboid pyrrhotite (opaque). Plane-polarized ansmitted light. Photomicrograph 10b: The pyrrhotite occurs as massive domain (e.g., in the upper part of this photomicrograph) and as amoeboid crystals intergrown with the silicates (in this case epidote). Plane-polarized reflected light. 33

34 5. Selected SEM-EDS Speca Table 2: List of selected SEM-EDS Speca, mineral determined and elemental content. Sample Specum Mineral Analyzed Elements Formula Bismuth Bi, Te Bi(Te) Bismuthinite Bi, S Bi2S Almandine/ Spessartine Si, Al, Mn, Fe, Ca (Fe, Mn)3Al2Si3O Bismuth Bi, Te Bi(Te) Bismuthinite Bi, S Bi2S Gold (elecum) Au, Ag Au(Ag) Pyrite S, Fe FeS Pyrrhotite S, Fe Fe1-xS 34

35 Sample 2: SEM-EDS backscattered image of bismuth (lighter grey) and bismuthinite (darker grey) intergrowths. The SEMEDS analysis of the points shown in this image are collected below. Sample 2 Specum 2.12: SEM-EDS Speca of bismuth. 35

36 Sample 2 Specum 2.16: SEM-EDS Speca of bismuthinite. 36

37 Sample 4: Photomicrograph of the garnet (see Photomicrograph 4c for details). The SEM-EDS specum is shown below. Sample 4 Specum 2.10: SEM-EDS Speca of garnet (spessartite/almandine). 37

38 Sample 7: SEM-EDS backscattered image of bismuth (lighter grey), bismuthinite (darker grey) intergrowth, and one gold particle precipitated within the fractured bismuthinite (Specum 2.19). The SEM-EDS analysis of the points shown in this image are collected below. Sample 7 Specum 2.17: SEM-EDS Speca of bismuth. 38

39 Sample 7 Specum 2.18: SEM-EDS Speca of bismuthinite. Sample 7 Specum 2.19: SEM-EDS Speca of gold (elecum). 39

40 Sample 8: SEM-EDS backscattered image of subhedral pyrite (darker grey) and anhedral pyrrhotite (lighter grey). Very finegrained gold particles are hosted within the pyrite and deposited at the contact with the pyrrhotite (yellow arrows). The SEM-EDS speca of the pyrite and pyrrhotite are shown below. The gold particles (yellow arrows), and galena (blue arrows) were analyzed and gave mixed speca. 40

41 Sample 8 Specum 2.24: SEM-EDS Speca of pyrite. Sample 8 Specum 2.26: SEM-EDS Speca of pyrrhotite. 41