The following are selected text excerpts from the November 6, 2000 Petrographic Report on 25 Polished Thin Sections by Vancouver Petrographics Ltd. on the Alto de Lipangue gold/copper property.
The complete report is available for viewing at the corporate offices of
Medinah Mining, Inc.

           

PETROGRAPHIC REPORT ON 25 POLISHED THIN SECTIONS
LIPANGUE AND LAS DOS MARIAS GOLD-COPPER
PROPERTIES
METROPOLITAN REGION, CHILE
FOR
Medinah Mining, Inc.

Report for: Les Price
Medinah Mining, Inc.
302-255 West 1st Street
North Vancouver, B.C.
V7M 3G8

November. 6, 2000.

SUMMARY:

The rocks in this suite of samples are mainly strongly altered, making recognition of primary lithology difficult. The first five samples, from 113 to 190 m, and the last sample at 325m, still display recognizable texture. In the upper 190 m, three of the samples (113, 170, and 190 m) appear to be a porphyritic to hypidiomorphic, clinopyroxene-?hornblende (or clinopyroxene-?orthopyroxene) bearing diorite to monzodiorite or (less likely) noritic leucomonzogabbro. The latter classification would result if the relict altered mafic in these rocks was orthopyroxene. These rocks are composed of seriate-textured to porphyritic oligoclase-andesine, clinopyroxene, and relict ?hornblende or ?orthopyroxene, now pseudomorphed by amphibole and chlorite, in a matrix of K-feldspar and minor quartz. The samples from 175 and 179 m differ in containing significant quartz (possibly mainly secondary in the former, but distinctly phyric and primary in the latter); these smaples, particulary the latter, could represent crystal-lithic tuffs. The last sample, from 325 m, is a seriate-textured quartz monzonite; note that since the amount and style of quartz in this sample are somewhat similar to that of quartz in many of the altered rocks higher up in the hole, it is possible that this could be a protolith for those samples. However, it appears to be somewhat less mafic than most of them, suggesting that a diorite or quartz diorite rather like that from 113.70 m or 317.35 m could also be a viable protolith.

There appears to be an increase in level of alteration in the sequence from about 200 m on, with increasing ?early potassic K-feldspar and quartz alteration replacing ?plagioclase, culminating in quartz-sulfide stockwork at 221-225 m and again around 290-310 m and 320-325 m. It is not clear that all or even most of the K-feldspar in these rocks is secondary since it is only rarely observed to be directly controlled by fractures or veins. Also, the presence of abundant primary or late-magmatic K-feldspar in the sample from 325 m, coupled with the difficulty of recognizing the primary lithology in these strongly altered rocks, raises the possibility that some or most of the disseminated K-feldspar is primary, derived from a rock such as the quartz monzonite at 325 m. However, against these arguments must be set the overall observation that K-feldspar is most abundant in the zone of most altered rocks (this can best be seen by laying out the stained offcuts).

Most of these (?potassic) altered rocks are also overprinted by an episode of phyllic (clay-sericite-chlorite-rutile, + quartz, calcite to ?ankeritic carbonate, sulfides) or locally ?advanced argillic alteration (possibly including ?pyrophyllite in addition to the phyllic mineral assemblage) that may be later than or ?partly synchronous with the ?potassic alteration. Outside the (?potassic)-phyllic zone (i.e. above 200 m, below 325 m and possibly in one sample from 299 m), alteration is mainly propylitic (chlorite-epidote-calcite) to transitional "mafic potassic"-propylitic (amphibole, alkali feldspar including K-feldspar, quartz, magnetite, sphene, apatite). Note that magnetite, common in the upper part of the hole, is destroyed in the central and lower parts of this zone (magnetite occurs from 170 to 213 m except for the crystal tuff at 179 m, and then not again until the last sample from 325.60 m).

Sulfides are mainly pyrite with minor to trace chalcopyrite and rare bornite; traces of Fe-poor (colourless) sphalerite, containing myriads of microscopic chalcopyrite blebs, are found in two samples (224 and 231 m); galena is found with sphalerite in 224 m. Chalcopyrite has more limited distribution than pyrite, and is commonly found associated with pyrite only in the vein or fracture zones in the sample rather than with the disseminated pyrite. Chalcopyrite is really only abundant in one very mafic sample (massive chlorite+calcite-quartz-rutile from 299 m). The bornite occurs in only one sample, from 175 m, also a relatively mafic rock altered to a ?skarn or "mafic potassic" assemblage including clinopyroxene, calcic plagioclase, epidote, quartz, magnetite, sphene and apatite.

Craig H.B. Leitch, Ph.D. P.Eng
492 Isabella Point Road,
Salt Spring Island, B.C. Canada
V8K 1V4

L00-13-113.70: PROPYLITIC-?POTASSIC (CHLORITE-KSPAR-EPIDOTE-CALCITE-AMPHIBOLE) ALTERED HORNBLENDE PYROXENE DIORITE OR ?NORITIC LEUCO-GABBRO

Hand sample is a grey-green, medium-grained intrusive rock of intermediate composition (mainly plagioclase and relict mafic minerals). The rock is not magnetic, but shows minor reaction to cold dilute HCl; minor yellow stain in the etched slab suggests K-feldspar replaces plagioclase. Modal mineralogy in polished thin section is approximately:

This sample is composed mainly of altered plagioclase and lesser elongated relic mafics, with a holocrystalline texture. Scattered opaques are mainly sphene and rutile.

Plagioclase about An25-30 forms mainly euhedral crystals up to 1.5 mm in diameter that are moderately altered (20-40% replaced) by epidote and by innumerable microfractures of K-feldspar or rare carbonate. Minor quartz, likely partly primary, forms irregular crystals up to 0.5 mm across in interstitial positions or partly intergrown with/replacing plagioclase.

There appear to have been at least two mafic minerals present. Relict clinopyroxene has euhedral outlines up to 1.5 mm in size, now partly replaced by zoisite and pale-coloured secondary amphibole plus lesser carbonate (likely calcite). Possible former ??orthopyroxene or ?amphibole now occurs as euhedral relics up to 1.5 mm long completely pseudomorphed by fine-grained chlorite, possibly with "hydrobiotite". Minor pale-coloured amphibole, likely secondary, is also associated with the latter mafic relics. The pseudomorphs have extinction parallel to their length and to the fibres of the chlorite, square cross-sections, and contain minute crystals of rutile. Larger aggregates of rutile in the cores of sphene aggregates up to 0.6 mm in diameter, are probably after original ilmeno-magnetite, of which rare tabular crystals up to 0.5 mm remain. Interstices between plagioclase and euhedral mafics are also filled by a second variety of chlorite.

In summary, this appears to have been a pyroxene-hornblende diorite or possibly leucocratic gabbro (even noritic gabbro if it did contain orthopyroxene rather than amphibole, as well as clinopyroxene). Original quartz content was probably less than 5%; the plagioclase composition may have been more calcic. Alteration is moderate propylitic or ?transitional potassic (chlorite/hydrobiotite, K-feldspar, epidote, amphibole, carbonate, quartz, rutile), but there is no sulfide. The K-feldspar could be late magmatic rather than hydrothermal in origin.

 L00-13-170.00: WEAK PROPYLITIC (CHLORITE-EPIDOTE-SPHENE/RUTILE) ALTERED, PORPHYRITIC ?PYROXENE MONZODIORITE OR ??NORITIC LEUCOGABBRO

Hand sample is a fine-grained, dark grey-green, slightly altered vaguely porphyritic intrusive rock. The rock is weakly magnetic but shows no reaction to cold dilute HCl, and minor yellow stain for K-feldspar in the etched slab. Modal mineralogy in polished thin section is approximately:

This slide consists of about 25% scattered plagioclase and 10-15% glomeratic clinopyroxene phenocrysts in a fine-grained groundmass.

Plagioclase phenocrysts (An45) are euhedral, up to 5 mm long, and show minor alteration to epidote/zoisite plus fracturing by a low-relief mineral (?Kspar or zeolite). Some crystals are strongly zoned, with narrow rims of ?oligoclase (see photomicrograph).

Clinopyroxene phenocrysts have euhedral but ragged (corroded) outlines up to 2 mm in diameter and are mantled by pale olive green amphibole (?hornblende) in parallel position. A separate type of relict mafic forms smaller crystals with euhedral outlines up to 1 mm in diameter, pseudomorphed by either secondary amphibole or chlorite-hydrobiotite as in the sample from 113.70. It is not clear if these were originally hornblende or ?orthopyroxene; the latter is suggested by the fact that they are more altered than the clinopyroxene in the same sample, and there is unaltered amphibole present in the section.

Scattered aggregates of sphene up to 0.7 mm across, commonly cored by minute crystals of rutile, likely represent the sites of former ilmenite; they are locally associated with euhedral magnetite to 0.4 mm in diameter, and trace chalcopyrite up to 75 microns long. Very rare chalcopyrite also forms minute blebs included in plagioclase.

The groundmass consists of euhedral plagioclase microlites, mainly <0.25 mm long but in places with a tendency to seriate texture (crystals up to 0.5 mm), with lesser euhedral clinopyroxene (<0.1 mm long), subhedral amphibole (<0.15 mm), and interstitial K-feldspar, chlorite, epidote and opaque oxides of finer grain size.

The ratio of total plagioclase to total feldspar of about 0.85 indicates that this rock may be classified as a porphyritic pyroxene monzodiorite (could have been leucocratic noritic monzogabbro if ?orthopyroxene were initially present). Alteration is propylitic, to chlorite-epidote-sphene/rutile + trace chalcopyrite.

L00-13-174.9: SKARN OR "MAFIC POTASSIC" (CLINOPYROXENE-PLAGIOCLASE-QUARTZ- EPIDOTE-APATITE-MAGNETITE-CHALCOPYRITE+BORNITE) ALTERED, QUARTZ-PHYRIC INTRUSIVE OR VOLCANIC ROCK

Hand sample is a mottled, grey-green, fine- to medium-grained, altered intrusive rock. Fine sulfides, including chalcopyrite (asociated with magnetite), accompany the mottling and a pale creamy-coloured, fracture controlled alteration that surrounds darker, rounded mottles. There is trace reaction to cold dilute HCl along hairline fractures, but no stain for K-feldspar in the etched slab. Modal mineralogy in polished thin section is approximately:

This slide consists mainly of a fine-grained intergrowth of clinopyroxene, plagioclase feldspar, quartz and magnetite averaging about 0.15 mm or less in diameter, and containing scattered quartz crystals with euhedral to subhedral outlines up to 1.5 mm in diameter. Rarely, remnants of twinned calcic plagioclase phenocrysts (An60) up to 1.5 mm long are visible.

The dark mottles, possibly representing sites of former mafic crystals, are now composed mainly of clinopyroxene (pale green ?diopside rarely over 0.1 mm in diameter), commonly with minor sphene of <30 microns diameter. The creamy-coloured areas surrounding the mottles appear to be composed mainly of secondary alkali feldspar, possibly of oligoclase composition to judge by the relief against quartz, and lesser pyroxene and quartz, all forming subhedra mainly <0.2 mm in size.

The dark mottles are generally centered on areas of disseminated or clotty magnetite, in places with associated sulfides, significant epidote and minor apatite. Magnetite forms subhedra generally <0.35 mm in diameter; chalcopyrite forms subhedra of similar size in places intergrown with bornite of similar size. Epidote forms subhedra up to 0.1 mm in size with pale yellow pleochroism indicating relatively low Fe, high Ca content; apatite forms subhedra to 0.2 mm in aggregates to 1 mm across. The lack of pyrite, presence of bornite with chalcopyrite suggest a low sulfide, low total sulfur part of a porphyry copper system, commonly found associated with magnetite.

Although remnants of the original ?intrusive or volcanic rock can be seen in places in the slide, this is clearly a strongly altered rock. Presence of phenocryst quartz suggests the protolith was different in composition from the samples at 113/170 m, more like the sample from 178.6. The alteration, to pyroxene, plagioclase, quartz, epidote, apatite, magnetite and copper sulfides, suggests a skarn or an unusual type of "mafic potassic" alteration in an island-arc porphyry copper system (somewat similar alteration is seen in some zones at Island Copper, B.C. and the Tanama and Helecho deposits in Puerto Rico).

L00-13-178.6: ?PROPYLITIC (ALKALI FELDSPAR-?QUARTZ-CARBONATE-EPIDOTE- CHLORITE-ZEOLITE-SPHENE-APATITE) ALTERED ?CRYSTAL LITHIC TUFF

Hand sample is a pale creamy to greenish coloured, medium-grained, felsic rock containing abundant crowded lithic clasts and crystal shards with a jumbled appearance like a crystal-lithic tuff, cut by a sheeted system of pale greenish-white veinlets. The rock is not magnetic but shows strong reaction to cold dilute HCl, and some yellow stain for K-feldspar in the etched slab. Modal mineralogy in polished thin section is approximately:

This slide is composed of tightly packed, abundant silicic-feldspathic lithic clasts mostly <0.5 cm in diameter and scattered quartz crystals or aggregates (?recrystallized crystals) mostly <2 mm in diameter. The rock is clast-supported, with very little matrix recognizable between the clasts.

The lithic clasts are composed mainly of either fine-grained quartz (probably mostly secondary; remnants of former plagioclase barely visible in some) or alkali feldspar and quartz. The latter commonly stain yellow in the etched slab, indicating that significant K-feldspar is present, which could be secondary (associated with the vein zone crossing the sample) but this is not obvious. Grain size form both quartz and feldspar in the clasts is generally <0.1 mm.

Clots of alteration minerals with irregular outlines up to about 1.5 mm across are composed of epidote, chlorite, apatite, carbonate and ?zeolite; relict plagioclase in some suggests they may be after former calcic plagioclase, but abundant sphene in others suggest derivation from former mafic crystals such as ?pyroxene. Negative relief of the plagioclase against quartz suggests it may be sodic (?oligoclase or albite), and in part secondary. It is not clear how much of the quartz is secondary, given the abundant quartz in many of the clasts.

Veins, up to about 1 mm thick, are composed mainly of carbonate (likely mostly calcite, subhedra to 0.5 mm) with minor epidote (subhedra <30 microns) and quartz (euhedra to 0.2 mm). In places the veins contain central fillings

In summary, strong propylitic alteration to alkali feldspar (mainly sodic, but possibly also including Kspar), epidote, chlorite, carbonate, zeolite, sphene, apatite, and possibly quartz, has made it difficult to guess the original protolith for this crystal-lithic tuff. It may have been of felsic to intermediate composition, depending on how much mafic material was present.

L00-13-190.4: WEAK PROPYLITIC (AMPHIBOLE-CHLORITE-EPIDOTE-CALCITE) ALTERED, PORPHYRITIC ?PYROXENE MONZODIORITE (OR ??NORITIC LEUCOGABBRO)

Hand sample is dark grey-green, fine-grained, massive porphyritic mafic to intermediate high-level intrusive rock. The rock is weakly magnetic, reacts to cold dilute HCl along narrow fractures, and shows minor yellow stain for K-feldspar in the groundmass of the etched slab. Modal mineralogy in polished thin section is approximately:

This slide is composed mainly of plagioclase and lesser clinopyroxene with a seriate to porphyritic texture. Plagioclase forms euhedral crystals ranging from phenocrysts up to 3 mm long down to groundmass crystals of less than about 0.5 mm, but ranging from 0.1 to almost 1 mm long. Plagioclase phenocrysts are zoned, with cores about An40 and rims about An20; alteration to epidote and carbonate is rare. Clinopyroxene forms euhedral phenocrysts (also oscillatory zoned) up to 2 mm long and smaller seriate subhedra mostly <0.5 mm in diameter. Pyroxene is occasionally rimmed or intergrown with olive-green amphibole subhedra up to the size of the pyroxene.

Interstices between plagioclase crystals are filled with small (mainly <0.3 mm diameter) subhedral altered mafic relics and 0.1 mm magnetite plus a mesh of anhedral K-feldspar to 0.15 mm, and minor sphene (subhedra to 50 microns, containing minute ?rutile) and quartz (irregular anhedra to 0.1 mm). The mafic relics are altered at the core to pale green chlorite, but the rims appear to be fibrous, olive-green to brownish ?secondary amphibole, plus minor epidote. Rectangular to square outlines suggest they could have been ?orthopyroxene; minor non-fibrous, fresh olive-green amphibole forming subhedra to 0.25 mm intergrown with the relics argues against the mafic relics having originally been hornblende. However, lath-shaped mafic relics partly replacing clinopyroxene, and now composed of clear, subhedral or in places fibrous secondary amphibole, show that hornblende is present. Thus the question of original ?orthopyroxene remains open.

In summary, this appears to represent a porphyritic pyroxene monzodiorite (or noritic leucogabbro if there originally was orthopyroxene present), with similarities to the sample from 170.0 m. Alteration is weak propylitic (secondary amphibole, chlorite, epidote, carbonate, sphene).

 L00-13-212.0: PHYLLIC (SERICITE-CHLORITE-PYRITE-RUTILE), POSSIBLY EARLIER POTASSIC (KSPAR-CHLORITE-MAGNETITE) ALTERED ?CRYSTAL TUFF

Hand sample is pale grey-green, fine-grained, massive, altered ?porphyritic felsic-intermediate ?volcanic or intrusive rock with small vugs and fine disseminated pyrite. The rock is slightly magnetic, shows no reaction to cold dilute HCl, but stains extensively for K-feldspar in the etched slab. Modal mineralogy in polished thin section is approximately:

This sample consists of variably altered plagioclase, relict mafic sites, and scattered quartz (?relict phenocrysts or shards). Although it is difficult to be sure due to the alteration, there is a vaguely tuffaceous texture to the rock.

Plagioclase appears to have formed sub- to euhedral crystals up to about 3 mm long that are now extensively replaced by fine-grained clay-sericite (flakes to 50 micron size) and, in many places, apparently by K-feldspar. The K-spar replacement is earlier than the clay-sericite, and spreads along cleavages throughout the plagioclase crystal, leaving vaguely twinned remnants. The K-feldspar could have been late magmatic in origin since it does not appear to be related to fractures or veins, or it may be hydrothermal, related to a structure larger than the scale of the hand specimen. Kspar also appears to form smaller crystals mixed with minor quartz as groundmass crystals that may be ?primary.

Mafic relics have subhedral outlines up to 1.5 mm long that are permissive of former ?pyroxene or amphibole. They are pseudomorphed by fine-grained (<0.1 mm) pale green chlorite and minor sericite, plus traces of rutile, sphene, magnetite and pyrite. Rare small apatite euhedra are up to 0.1 mm long, and rare euhdral zircon are <75 microns long. Euhedral to subhedral magnetite crystals are mainly <0.2 mm in size. Rutile forms subhedral aggregates up to 0.85 mm across of minute euhedra. Scattered euhedral pyrite crystals are mostly <1 mm in diameter; rare chalcopyrite up to 40 microns in diameter is associated with chlorite.

It is not clear what the protolith for this phyllic (sericite-chlorite-pyrite-rutile+sphene) altered rock was; also, there may have been minor potassic (Kspar-magnetite) alteration prior to phyllic alteration, which the chlorite would fit better with. It is vaguely tuffaceous or porphyritic, and contains phyric quartz like samples from 174.9 and 178.6; it may have been a crystal tuff of intermediate composition.

L00-13-213.0: PHYLLIC (SERICITE-CHLORITE-CARBONATE-PYRITE-RUTILE), POSSIBLY EARLIER POTASSIC (QUARTZ-KSPAR-?MAGNETITE) ALTERED ?CRYSTAL TUFF

Hand sample is grey-green, massive,medium-grained, vaguely tuffaceous or porphyritic ?volcanic or intrusive rock, slightly bleached towards a fracture coated with white sericite or ?clay. The rock is weakly magnetic, shows strong reaction to cold dilute HCl, and strong yellow stain for K-feldspar in the etched slab. Modal mineralogy in polished thin section is approximately:

This sample consists mainly of relict altered feldspars, relict mafic sites, and quartz. The alteration is intense enough to conceal primary textures, so that it is not clear whether it is a crystal tuff or a porphyritic intrusive.

Relict feldspar crystals have euhedral to somewhat ragged outlines up to almost 3 mm long. Vaguely defined relict twinning and the shapes suggest most were probably originally plagioclase; however, most are now replaced by secondary alkali feldspar that stains yellow for K-spar in the etched slab. Most of this secondary alkali feldspar is also altered by fine-grained sericite or clay, but this appears to be an overprint. The K-feldspar is not clearly secondary hydrothermal in origin (not related to veins or fractures); it could be late magmatic, or the controlling structure could be larger than the scale of the hand specimen available.

Quartz is abundant, forming mainly subhedral to anhedral crystals up to about 1 mm in diameter that poikilitically enclose other crystals and commonly have overgrowth rims, suggesting some may be secondary in nature. Again, as for K-spar, the period of quartz overgrowths may have been late magmatic rather than hydrothermal. Narrow quartz veinlets <0.1 mm thick are rare, but in places they grade into irregular areas of fine-grained quartz in a reticulate network.

Relict mafic sites with non-definitive ragged, irregular outlines mostly less than 1 mm in diameter, are pseudomorphed by chlorite, carbonate (possibly calcite and ?ankerite), sericite and rutile, or less commonly magnetite or pyrite. Cores of the pseudomorphs tend to be chlorite and minor sericite; rims tend to be carbonate. Rutile aggregates may be up to 1 mm across, composed of minute <30 micron crystals. Magnetite forms subhedra up to 0.25 mm in diameter; pyrite euhedra are mainly <0.15 mm in diameter.

This sample appears to represent a ?crystal tuff (or ?high-level porphyritic intrusive) of intermediate composition that has undergone extensive replacement by quartz and Kspar (magnetite may be partly secondary and have formed during this stage), followed by phyllic alteration to sericite, chlorite, carbonate, pyrite and rutile.

L00-13-215.95: PHYLLIC (SERICITE-CHLORITE-PYRITE-SPHENE/RUTILE), POSSIBLY EARLIER POTASSIC (KSPAR-QUARTZ) ALTERED ?CRYSTAL TUFF

Hand sample is grey-greenish to creamy-buff in colour, fine- to medium-grained, with an altered ?porphyritic or tuffaceous texture, minor irregular quartz veins, and disseminated sulfides. The rock is not magnetic and shows no reaction to cold dilute HCl, but there is abundant stain for K-feldspar in the etched slab. Modal mineralogy in polished thin section is approximately:

This slide is similar to the previous slide, composed of abundant relict K-feldspar, lesser quartz, sericitized relict ?plagioclase sites, and minor chlorite, pyrite and sphene/rutile after mafic minerals. It is so strongly altered that the original texture is difficult to discern, suggestive of either a crystal tuff or a porphyritic high-level intrusive rock.

Sericite (and ?clay) altered plagioclase sites have subhedral outlines up to 0.5 cm long that are pseudomorphed by 10-20 micron flakes. Other, vaguely defined sites of similar shape and size appear to be replaced by K-feldspar, quartz and sericite. The K-feldspar forms subhedral crystals mainly <0.5 mm in diameter, themselves partly replaced by fine subhedral flakes of sericite. In places what appears to be relict twinning, mimicked by lath-shaped Kspar and quartz, suggests that the Kspar and quartz has replaced original plagioclase. If so, then this sample displays very strong potassic alteration, later overprinted by phyllic alteration. The ?potassic alteration is pervasive; the phyllic alteration appears to increase towards one end of the slide, probably near a later fracture.

Quartz forms irregular, corroded-looking ?relict primary crystals up to 3 mm in diameter, in places with what appear to be minor overgrowths at the margins, and abundant finer-grained material in the matrix of the rock that is clearly secondary in places (distributed along narrow veinlets up to 1 mm thick, with strongly altered margins).

Mafic sites are less well-defined, consisting of irregular patches up to about 1 mm across of slightly coarser-grained (<0.3 mm) sericite or muscovite, in places with chlorite up to 0.1 mm, and variable amounts of sphene (subhedra to 0.4 mm, in places with included minute rutile), or pyrite (euhedra mostly <0.35 mm in diameter). Rare zircon forms euhedra to 40 microns diameter.

L00-13-219.70: PHYLLIC (SERICITE-CHLORITE-CARBONATE-PYRITE-RUTILE) AND EARLY ?POTASSIC (KSPAR-QUARTZ) ALTERED ?CRYSTAL TUFF OR INTRUSIVE

Hand sample is medium-grained and massive, with an altered, vaguely porphyritic texture, containing relict mafics cored by dark green chlorite and rimmed by buff-brown ?ankerite. The rock is not magnetic and shows no reaction to cold dilute HCl, but there is abundant stain for K-feldspar in the etched slab. Modal mineralogy in polished thin section is approximately:

This slide is composed of large subhedral crystals of simple Carlsbad twinned K-feldspar up to 2.5 mm long, sericitized and chloritized ?mafic crystal relics, and interstitial quartz.

The K-feldspar in places reveal traces of relict twinned ?plagioclase within them, suggesting that the Kspar has replaced formerly more extensive plagioclase feldspar.

Quartz mostly forms subhedral to irregular crystals that are optically continuous for up to 1 mm and appear to be replacing or overgrowing surrounding feldspar.

Sericite-carbonate-chlorite altered relics have euhedral squarish outlines up to 2 mm across; they may have been ?plagioclase or mafic crystals. Chlorite-altered relics have irregular outlines up to 3.5 mm across, likely after former mafic minerals. Chlorite, forming subhedral flakes mostly <0.15 mm in diameter, tends to form the cores of the relics, with carbonate (and rutile) at the rims. Carbonate, forming subhedra mostly <50 microns in diameter, is likely dolomite or ankerite since it does not appear to reaxt to HCl in hand specimen.

Pyrite forms coarse euhedral cubic crystals up to 1 mm in diameter, locally aggregating to several mm across. Rutile occurs as minute subhedra, possibly with traces of sphene, commonly enclosed in carbonate.

It is difficult to tell, given the level of alteration, but this sample appears to have been a ?tuffaceous rock, perhaps a crystal tuff of mafic to intermediate composition (although the texture is also permissive of a porphyritic intrusive). It has undergone significant ?early potassic alteration to K-spar and quartz, overprinted by later phyllic alteration to sericite, chlorite, pyrite, dolomitic carbonate and rutile.

L00-13-221.50: INTENSE PHYLLIC (QUARTZ STOCKWORKED, CLAY-SERICITE-CHLORITE- CARBONATE-RUTILE-SULFIDES) AND ?EARLY KSPAR ALTERED IGNEOUS ROCK

Hand sample appears to be a hydrothermal breccia, composed of angular, irregular, vaguely defined blocks of rock in a matrix of quartz veins. The included blocks of rock are greenish and buff-brown, similar to the previous sample (219.70); significant pyrite is associated with the quartz vein stockwork. Core areas of the blocks stain yellow for K-feldspar in the etched slab, suggesting outer rims of the blocks have been overprinted by silicification. Modal mineralogy in polished thin section is approximately:

Remnants of wall rock in this sample consist of rounded to irregular-shaped patches of clay-sericite, chlorite, carbonate, and rutile with relics of K-feldspar, all replaced by and separated by irregular masses of quartz. The texture of the former rock is virtually destroyed at the thin section scale. Former ?plagioclase crystals appear to be completely replaced by clay-sericite (microscopic flakes rarely over 15 microns in diameter), in places intimately mixed with chlorite of similar size. Even K-feldspar crystals, with subhedral outlines up to 1 mm across, are partly to mostly replaced by clay-sericite. Former ?mafic crystals are pseudomorphed by patches of chlorite (flakes up to 25 microns in diameter), carbonate (likely dolomite or ankerite, subhedra to 25 microns), and abundant rutile or leucoxene (anhedral patches up to 0.2 mm across composed of mostly amorphous material).

The intervening stocwork areas are composed of anhedral to subhedral interlocking secondary quartz crystals with minor clay-sericite, chlorite, sulfides and rutile interstitial to the quartz. It is not possible to be sure, but it appears that silicification and clay-sericite-chlorite-pyrite-rutile alteration spread out from the quartz stockwork. (An alternative would be that secondary quartz accompanied the K-feldspar alteration, which appears to be earlier.)

Pyrite, forming large subhedral crystals up to 2 mm across, and traces of chalcopyrite, forming anhedral crystals mostly <0.2 mm across, are found in both the quartz stockwork and the altered wall rock fragments; chalcopyrite is closely associated with chlorite, and probably represents replacement of former mafic minerals. Note that minor amounts of chalcopyrite present as minute (<20 micron) crystals encapsulated in quartz might not be liberated even during fine grinding of the rock.

L00-13-224.20: INTENSE PHYLLIC (QUARTZ STOCKWORKED, CLAY-SERICITE-CHLORITE- RUTILE-SULFIDES) AND ?EARLY KSPAR ALTERED IGNEOUS ROCK

Hand sample is similar to 221.50, consisting of angular, pale green altered fragments in a quartz vein matrix or stocwork. Minor pyritic sulfides are associated with the stockwork, and minor buff-coloured ?carbonate occurs with the chloritic fragments. The fragments show abundant yellow stain for K-feldspar in the etched slab. Modal mineralogy in polished thin section is approximately:

Wallrock fragments are mostly composed of large irregular-shaped patches, up to 2 mm across, of clay-sericite and lesser chlorite that appear to be replacing feldspar (mostly K-feldspar to judge by the extent of yellow stain in the etched slab). These patches are intergrown with secondary quartz as sub- to anhedral crystals up to 2.5 mm in diameter with ragged margins suggesting they are overgrowing the adjacent minerals. Sericite flakes are rarely up to 35 microns in diameter, mixed in places with a very pale greenish or brownish chlorite of similar size. Most chlorite, however, is bright green, forming flakes up to almost 100 microns in diameter at the edges of chloritic patches. Minor rutile is mixed with the chlorite as irregular aggregates up to 0.5 mm across composed of almost amorphous material (leucoxene).

The quartz stockwork is composed of coarse subhedral crystals up to almost 0.5 cm in diameter. Minor amounts of clay-sericite and chlorite are found along the boundaries between the crystals.

Sulfides, principally coarse euhedral pyrite as cubes up to 4 mm across, tend to line the margins of wall rock fragments at the contact with quartz vein stockwork. The pyrite contains abundant inclusions of silicates and rutile, and in places is associated with traces of chalcopyrite, sphalerite and galena. Sphalerite is associated with traces of galena and chalcopyrite, and contains abundant submicroscopic inclusions of chalcopyrite (see photomicrograph). Chalcopyrite is also found as minute (<25 micron) blebs in the highly altered wallrock, especially hosted in chlorite.

The original protolith is not determinable due to the intense phyllic (quartz-clay-sericite-chlorite- pyrite-rutile) and possibly earlier ?potassic (K-spar, quartz) alteration.

L00-13-229.10: INTENSE PHYLLIC (CLAY-SERICITE-CHLORITE-PYRITE-RUTILE) AND ?EARLY KSPAR ALTERED/RARELY QUARTZ-KSPAR VEINED ?INTRUSIVE ROCK

Hand sample is a greenish grey, massive, medium-grained, altered, pyritic ?intrusive or tuffaceous rock cut by narrow white veins that stain yellow for K-feldspar, as does much of the matrix of the rock. Modal mineralogy in polished thin section is approximately:

This sample consists of irregular-shaped patches of clay-sericite altered feldspar (probably after both K-feldspar and plagioclase), subhedral to irregular patches of chlorite and lesser clays-sericite (after former mafics), all strongly overprinted by secondary quartz that may have grown outwards from clumps of primary quartz.

K-feldspar, indicated by the yellow stain in the etched slab, is difficult to recognize in thin section. It appears to form subhedral crystals up to about 1 mm in diameter, that are mostly about half replaced by clay-sericite and minor chlorite, with a lamellar texture that may reflect primary plagioclase twinning. This suggests that the K-feldspar may be largely secondary, having replaced former plagioclase in an early potassic phase of alteration. Some of the secondary quartz, which forms subhedral crystals up to 2 mm across that poikilitically enclose other minerals around their margins, may have formed at that time, but it is difficult to be sure. The possibility of the K-spar being secondary is supported by the presence of K-feldspar as euhedral crystals up to 0.25 mm diameter, intergrown with quartz, along narrow veinlets <1 mm thick.

Most of the clay-sericite has negative relief compared to quartz and chlorite, but moderate birefringence, suggesting that some or all of it could be a montmorillonite- or smectite-group (swelling) clay. Individual flakes are generally <20 microns in diameter.

Mafic relics are pseudomorphed by chlorite as subhedral flakes mostly <25 microns in diameter, in places with a rim of clay-sericite or mixed intimately with clay-sericite. Clusters of rutile up to 0.2 mm across, commonly asociated with the chloritized mafics, are composed of euhedral dark brown crystals mostly <75 microns in size. Pyrite occurs as cubic euhedra mostly <1 mm in diameter, also commonly associated with the chloritized mafics. Rarely, traces of chalcopyrite form subhedra to 0.15 mm associated with the pyrite crystals, and traces of ?galena are included in the pyrite crystals.

It is not clear what the original protolith for this intensely phyllic (quartz-clay-sericite-chlorite-sulfides-rutile) and possibly earlier potassic (Kspar-quartz) altered rock was; it may have been a mafic-intermediate intrusive rock.

L00-13-231.05: INTENSE PHYLLIC (?QUARTZ, CLAY-SERICITE-CHLORITE-PYRITE-RUTILE) AND ?EARLY KSPAR-QUARTZ ALTERED ?INTRUSIVE ROCK

Hand sample is a medium grained, greenish, mottled (strongly altered) ?igneous rock of intermediate to mafic composition, cut by veins up to 0.7 cm thick containing massive pyrite. Minor stain for K-feldspar in the etched slab suggests that K-spar is in part controlled by the veins and therefore is secondary. Modal mineralogy in polished thin section is approximately:

This sample is similar to the previous six or seven samples, with intense alteration obscuring primary lithology of a fine-grained ?intrusive rock. Irregular-shaped patches of clay-sericite or chlorite and pyrite+rutile, or mixtures of chlorite and clay-sericite, are embedded in a matrix of quartz (possibly largely secondary), K-feldspar and chlorite. It is possible that the larger patches, about 2 mm in diameter, represent former phenocrysts of either mafic or feldspar crystals (or both) but this is not certain since the texture could be merely due to alteration.

K-feldspar is difficult to recognize in thin section due probably to strong replacement by clay-sericite, which forms minute (5 micron) to fine-grained (25 micron) flakes. The shapes of former feldspar crystals are obscured by strong replacement around the margins by secondary quartz. The quartz crystals commonly have subhedral outlines that are optically continuous for up to 1 mm, poikilitically enclosing altered feldspar remnants or chloritized mafic relics. It is not clear how much, if any, of the quartz may have been primary.

Chlorite forms pale green flakes up to 75 microns in diameter, commonly containing or associated with pyrite and rutile. Yellowish-brown rutile forms euhedral crystals up to 0.1 mm diameter, in places aggregating to 0.25 mm.

Narrow irregular discontinuous quartz veinlets up to 0.1 mm thick cross the rock. The major vein is composed of pyrite, with quartz and chlorite selvages, and appears to have a concentration of K-feldspar in envelopes along one side of the vein, and clay-sericite-chlorite on the other side.

Pyrite, forming euhedral crystals up to several mm across in massive aggregates in the major vein, or millimeter-sized crystals in the wallrock, is rarely associated with or contains rounded inclusions of sphalerite up to 0.75 mm across. The sphalerite is colourless (Fe-poor) but contains abundant round blebs of chalcopyrite <10 microns in diameter.

L00-13-241.30: PHYLLIC (CLAY-SERICITE-CHLORITE-?QUARTZ-PYRITE-RUTILE) AND ?EARLY KSPAR ALTERED IGNEOUS ROCK CUT BY QUARTZ-CHLORITE-PYRITE- CHALCOPYRITE ZONE

Hand sample is greenish-grey and strongly altered, with a mottled to disrupted appearance, cut by irregular zones with pyrite and chalcopyrite that are associated with stronger chloritization. There is extensive pale yellow stain for K-feldspar in the etched slab, likely pale coloured due to clay-sericite alteration of the feldspar. Modal mineralogy in polished thin section is approximately:

The major altered zone (not a vein) is composed of coarse-grained subhedal pyrite (aggregates up to 4 mm across) with associated chalcopyrite (subhedra to 1.2 mm) in a matrix of secondary quartz (subhedra to 2.5 mm diameter) and chlorite (bright green rosettes up to 0.25 mm in diameter) plus lesser clay-sericite. In places the clay-sericite has a radial rosette-like habit that is similar to pyrophyllite (characteristic of a highly aluminous assemblage, but it cannot be identifed with certainty except by microchemical tests such as scanning electron microscope, or SEM).

Away from the major altered zone, the wallrock consists mainly of relict patches of strongly clay-sericite altered feldspar (partly K-feldspar to judge by the yellow stain in the etched slab) and chlorite-rutile altered mafic relics, both intensely overprinted by secondary quartz. Some or most of the K-feldspar may be secondary; it appears to predate the phyllic (clay-sericite) alteration. Note that the quartz overprint may have accompanied the early