Ultramafic Intrusions, Detailed Geology and Geobarometry of the Jurassic Bonanza Arc in the Port Renfrew Region, Southern Vancouver Island (NTS 092C)
D. Canil, School of Earth and Ocean Sciences, University of Victoria, Victoria, BC; [email protected]
D. Canil (2010): Ultra mafic intrusions, detailed geology and geobarometry of the Ju ras sic Bo nanza Arc in the Port Renfrew region, southern Van cou ver Is land; in Geoscience BC Sum mary of Ac tiv i ties 2009, Geoscience BC, Re port 2010-1, p. 141–148.
Introduction Survey Methods
Sev eral iso lated bod ies of ultram afic rock were discov ered Bedrock geol ogy was mapped at 1:25 000 scale on Terrai n in the Port Renfrew area of southern Vancou ver Island over Resource Inven tory Mapping (TRIM) map sheets and com - the past nine years by G. Pearson. A field mapping study piled to 1:50 000 scale (Figure 1). Sam ples for thin-sec tion jointly funded by Geoscience BC and Em eralds Fields Re- pe trog ra phy, geo chem is try, fire as say and geo chron ol ogy sources was con ducted to as cer tain the ar eal ex tent of the were taken (Fig ure 2). De tailed ex am ina tions of se lect ultra mafic bod ies and to de ter mine their re la tion ship with ultram afic bodies could not be com piled onto the 1:50 000 other rocks of southern Vancou ver Island. The objec ti ve scale ge ol ogy maps but are described in de tail in re lated pa - was to use this and other petro log i cal infor m ati on from the pers (Larocque and Canil, 2007, 2009). surround ing area to assess the econom ic signif i canc e of the ultra mafic bod ies as a po ten tial target for Ni-Cu or plat i - Regional Geology Overview num-group el em ent (PGE) de posit s, and the overall struc - tural thickness and set ting of the Juras sic Bonanza Arc. Pre vi ous geo log ical maps in the area were mapped at This re port sum ma rizes re sults of the geo log i cal field work, 1:100 000 scale and com piled to 1:250 000 scale (Mul ler, includ ing detai led mapping, sampling, geobarometry and 1983). Most of the area is under lai n by rocks of Wrangellia. geochemical assays of the ultramafic rocks. The De vonian Sicker Group forms the base ment to Wrangellia on Vancou ver Island, and consis ts of mafic and Field Area and Access fel sic vol canic and volcaniclastic rocks, over lain by The field area on southern Vancou ver Island (NTS 092B, C, epiclastic and car bon ate sed im en tary rocks of the Permian F, G) is bordered by the San Juan River to the south, Buttle Lake Group. Uncon form ably overly ing the Buttle Cowichan Lake to the north, Nitinat Lake to the west and Lake Group are the Tri as sic Karmutsen bas alts, in turn the Fleet River to the east (Fig ure 1). The area of in ter est is overlai n by the Quatsino Form ati on, a thin (<75 m) se- in and surround ing the NTS 092C map area. The physi og - quence of micritic limestone . The Parsons Bay Form ati on, raphy of the area is one of gener all y steep forest ed slopes, a 35 m thick se quence of thinly bedded ar gil laceous divided by streams cut ting through bedrock and allu vium to mudstone, limestone , siltstone and sandstone , conform ably cre ate con sid er able re lief. Open val leys are pres ent along overli es the Quatsino Formation (Nixon and Orr, 2007). the San Juan River and to a lesser degree along the Gordon The Port Renfrew region is under lai n mostly by rocks of the River. Juras sic Bonanza Arc, which intrude s, as well as uncon - The area is ac cessed by a net work of logging rods in vari ous formably over lies, the older units of Wrangellia. Clastic states of pres er va tion. Over all, bed rock ex po sures are best sedi m entar y rocks of the Oligocene Carmanah Group un- along acti ve logging roads and in ele vate d areas that have conform ably overli e all older units along the western coast been recently logged. Most ar eas were ac cessed by four- of the is land. Qua ter nary gla cial till and al lu vium covers wheel drive truck, but a few rem ote mountai ntops with stream valleys. over grown logging roads could be ac cessed only by helicopter. Jurassic Bonanza Arc In the field area, rocks of the Bo nanza Arc are sep arated from the Ju ras sic-Cre taceous Pacific Rim Terrane to the south by the San Juan fault and from the Sicker Group to the north by the Cowichan fault. The Juras sic -aged rocks of the Keywords: ultra mafic, arc, Ju rassic, nickel, Bo nanza, geo bar- ometry Bonanza Arc in Wrangellia include , from base to top, the This publi ca tion is also avail able, free of charge, as col our digi tal Westcoast Crys tal line Com plex (WCC), the Is land files in Adobe Ac robat ® PDF for mat from the Geoscience BC Plutonic suite and the Bonanza Group volcanics. These website: http://www.geosciencebc.com/s/DataReleases.asp. rocks have under gone ze oli te- to local ly greenschist-fa cies
Geoscience BC Re port 2010-1 141 Fig ure 1. Geol ogy of the field area and loca tion of the field area (in set map), south ern Van cou ver Is land, Brit ish Colum bia. The cross-sec tion (lower left) is along the line of A-A’. The region was mapped at a scale of 1:20 000 and com piled to 1:50 000 scale. Also shown for ref erence are the town of Port Renfrew, Nitinat Lake, Cowichan Lake and the trace of the ma jor struc tures (San Juan fault and Cowichan up lift).
Fig ure 2. Areas tra versed with all sam ple lo ca tions (red in verted tri angles), the main line for estry roads (red lines) and ultra mafic out crop lo ca tions (black cir cles), south ern Vancou ver Is land, Brit ish Co lum bia. The box in the cen tre shows the lo ca tion of the Pearson claim block.
142 Geoscience BC Sum mary of Ac tiv i ties 2009 meta mor phism, but orig i nal ig ne ous lithological names are meta morphosed na ture of these carbon ate rocks, they are used in their description. here suggest ed to repre sent fragm ents and/or faulted slices of carbon ate rocks be longing to the Perm ian Buttle Lake Westcoast Crystalline Complex Form ati on or the older Sicker Group, which are now screens or septa in the intrusive rocks of the WCC. The Westcoast Crys tal line Complex (WCC) rep re sents the deep est pre served struc tural level of the Bo nanza Arc and is Ultramafic Rocks dom inantl y quartz diorite and gabbro with vary ing amounts of hornblende, bi oti te, orthopyroxene and The larg est con cen tra tions of ultra mafic rocks are pres ent clinopyroxene with ac ces sory mag ne tite, il men ite, py rite along the Granit e Creek mainli ne and at the top of Fairy and pyrrhotite. Weakly concor dant diabase bodies are mountai n (Figure 2). Other bodies are recog nize d west of found local ly in the WCC in the field area southwest of the the Griersen main line in the Twin Lakes area. Details of Gordon River. Grain sizes vary from fine grained to pegma- their geochem istry , petrol ogy and ori gin can be found else- toid and are het er o ge neous over a scale of metres. where (Larocque, 2008; Larocque and Canil, 2009)
Disti nct units of light grey im pure marble 3–10 m thick oc- Ultra mafic rocks oc cur as discrete bod ies within the WCC cur in the diorite. Some mar ble units can be traced for a few diorite, ranging in size from a metre to several tens of kilo metres along an ori en ta tion par al lel to re gional strike. metres. Al though their borders are often obscure d by over- Mar ble out crops found in the east ern part of the field area bur den, there is some lat eral con ti nu ity or con cen tra tion of are more ir reg u lar in out crop pat tern. Mi nor mag ne tite-rich the ultra mafic bodies over distanc es of up to 1 km. Contac t skarn bod ies, with vari ably de vel oped di op side-gar net and re la tion ships be tween the ultra mafic bod ies and the WCC mag ne tite-chal co py rite-py rite as sem blages, are found at diorite are quite variable . Smaller bodies , which tend to be the contac t of diorite or diabase with the marble. Due to the more ol ivine rich, have either abrupt, undeformed contac ts
Fig ure 3. Regional aero mag netic map (from BC Geo log i cal Sur vey, 2009) su perim posed on lo ca tions of ultra mafic rocks (grey cir cles) in the map area, south ern Vancou ver Is land, Brit ish Co lum bia.
Geoscience BC Re port 2010-1 143 with their host or are pres ent as sheared pods. Larger bod- Bonanza Volcanics ies, which are mostly ol ivine gabbro, grade into the diorite The Bo nanza volcanics are only very weakly metam or - of the WCC. In sev eral lo ca tions, the as so ci a tion of ol iv ine phosed, dis play ing as sem blages in dic a tive of the ze o lite fa- pyroxenite with pegmatitic hornblende diorite has been cies and varying from aphani ti c basal t through plagioclase- noted. , pyroxene- and/or hornblende-phyric ande sit e to minor dacite and lesser pyroclastic de pos its. The lat eral ex tent In thin sec tion, peridotite and oliv ine pyroxenite consis t of and con ti nu ity of these de pos its is ob scured by veg e ta tion vari ably serpentinized cu mu lus ol iv ine with in clu sions of and over bur den. No con tacts be tween Bo nanza vol ca nics euhedral spinel, poikolitically enclos ed by either orthopyr- and plutonic rocks were observed. oxene, am phibole, or more rarely, clinopyroxene. Orthopyroxene and clinopyroxene coex ist in several sam - Geochronology ples. Weakly to strongly altered plagioclase is pres ent as an intercumulus phase in some sam ples. In these sam ples, ol- Geo chron ol ogi cal in ves ti ga tions were un der taken to con- iv ine is never di rectly in con tact with plagioclase, and is al - strain the age of rocks that host the ultram afic bodies . Four ways mantl ed by a corona of pyroxene. Where pres ent, am - samples were ob tained in dif fer ent parts of the map area and phibole appears as the result of reac ti on with pyroxene, were subm it ted for age dating by the U-Pb zircon method at along grain boundari es or along exsolution lamellae. Igne - the Pa cific Cen tre for Iso to pic and Geo chem i cal Re search ous phlogopite is also pres ent as a minor phase in some (PCIGR) at The Univer sity of Brit ish Co lumbia. The ages samples. ob tained as of this writ ing are still pre limi nar y but the range in U-Pb ages of zircons is betwee n 194 and 174 Ma (Ta- Gabbro and gabbronorite dis play cum ulus plagioclase, ble 1). In the WCC near Lens Creek in the southeas tern part plus or minus orthopyroxene, clinopyroxene and, in one of the map area, melanodiorite is crosscut by a dike of case, ol ivine. Much of the postcumulus clinopyroxene has leucodiorite. Both the leuco- and melanodiorite returned been replaced by amphi bole. Plagioclase in these sam ples ages of 174 Ma. In the southwest , mylonitized diorite near is in variably less al tered than in the peridotite and ol iv ine Twin Lakes has an age of 194 Ma. Further west, an pyroxenite sam ples. Chrom ite is the dom inant opaque undeformed granodiorite pluton near Glad Lake also re- phase in the ultra mafic samples. Mag ne tite with mino r il - turned an age of 192 Ma. Thus, magmatism spans an age of menit e exsolution is both a euhedral and intercumulus at least 20 Ma. All the ages ob tained in this study fall within phase in the gabbroic rocks. Mi nor amounts of chalco py rit e those of the Bonanza Arc elsewhere along strike in the Port are noted in most sam ples. Rare inclu sions of round, white, Alberni and Bamfield ar eas (DeBari et al., 1999). Be cause high-re flec tivity grains in ol iv ine (pos si bly iden ti fied as the diorite host ing ultra mafic rocks along both the Granit e pentlandite) are also noted. Creek mainli ne and on top of Browns mountai n is identi cal to that for which ages were obtai ned, the ultram afic rocks in Re gional-scale aero mag net ic data avail able for south ern the Port Renfrew area are al most cer tainly Ju ras sic in age Vancou ver Island shows a prom inent magneti c high, run- and are re lated to the Bo nanza Arc. A Ju ras sic age rules out ning par allel to, and extend ing north from, the San Juan that the ultra mafic rocks are cumulate blocks from the older fault. At this res olu ti on, the magneti c anom aly appears to Triassic Karmutsen lavas. roughly corre spond to areas under lai n by the WCC (and ultra mafic) rocks (Fig ure 3). Structural Geology Foliations within the WCC rocks are define d by a planar Island Plutonic Suite fabric of hornblende or bi oti te, or by a gneissosity of mafic and fel sic lay ers, and gener all y strike northwest and dip The Is land Plutonic suite occurs as a roughly southeas t 60–75° to the southwest . Poles to foliations in the WCC be- aligned se ries of medium -grained plutons ranging in com - tween Gordon River and Harris Creek (Figure 1) define a posi ti on from quartz diorite to alkali feldspar granit e. The great cir cle with a pole plunging approx i m ately 50° to the Island Plutonic suite most com monly intrude s the Trias sic south-southeas t (Figure 4). Well-devel oped minor folds in Karmutsen basalt s, and is dis tinguishe d from plutons of sim i lar com po si tion of the WCC by lacking any foli ati on. The contac t betwee n the Island Plutonic suite and the WCC Table 1. Uranium-lead zircon ages for samples from the Bonanza Arc in the Port Renfrew region, southern Vancouver Island, British is not well define d. In the field area, rocks of the Island Columbia. Plutonic suite occur mainly in the northern and east ern parts of the field area, sep arated from the WCC to the south - Location Sample Number Rock type U-Pb age (Ma) Lens Creek JL110B leucodiorite 174.1 ÿ±0.4 west by inter vals of Karmutsen basal t and Quatsino lime- Lens Creek JL110 melanodiorite 174.8 ÿ±0.5 stone, which are in fault contac t (to the southwest) with Twin Lakes DC0507 diorite mylonite 193.7 ÿ±0.5 rocks of the WCC. Glad Mainline DC0637 granodiorite 192.6 ÿ±0.4
144 Geoscience BC Sum mary of Ac tiv i ties 2009 The com mon orien ta ti on and sense of shear (tops to north - east) in both the mylon it e near Twin Lakes and the Harris Creek–Hemmingsen shear zone suggest that the WCC oc- curs as a se ries of east-verging thrust-faulted panels . At least two major thrust-faulted pan els are rec og nized: the wester nm ost panel thrusts the WCC over itsel f, and the eastern most panel places the WCC onto the Karmutsen basalt s and the Quatsino limestone (Figure 1). In this way, it is pos si ble that the WCC is an imbrication of several thrust- faulted panels , but some of the faults are not recognized due to cover.
Downplunge projec ti ons of the rock units (along a fold axis plunging 50° to the south-southeas t) suggest that at least 15 km of struc tural depth is exposed in the Juras sic units throughout the enti re field area. This is gener all y con sis tent with pres sures of crys tal li za tion ob tained by aluminum-in- hornblende geobarometry on granodiorite and diorite plutons in the map area along a line norm al to regional strike from Twin Lakes in the west to Cowichan Lake in the Fig ure 4. Stereonet projec tion of poles to foliations for WCC diorite in the area be tween Gordon River and Har ris Creek. Poles to east. foliations de fine a gir dle hav ing a pole (b) that defines the re gional fold axis (plung ing 50° to the south-south east). Mi nor folds in Geobarometry diorite on Fairy mount ain and near Twin Lakes have nearly identi cal ori en ta tions. The overall thickness of the enti re Bo nanza Arc secti on on Vancou ver Island is not known due to a lack of constra ints the WCC are evi dent on Browns mountain and near the on its structura l thickness. This porti on of the study ad- Twin Lakes re gion, and have axes plunging with nearly dressed this problem by esti mating the rel ati ve depth of ex- identi cal orien ta ti ons as the major fold axis in Figure 5. posure and struc tural thickness in the Bonanza Arc using alum inum -in-hornblende barom e tr y of its felsic plutons. Coupled with geolog i cal data, the struc ture of exposed arc The map pat tern of the same rocks northwest of the Gordon crust com prising Vancouver Island is assessed. River mainline, how ever, is more con sis tent with closed folds but plunges northwest rather than southeas t. One pos- Fel sic rocks were sampled from dif fer ent parts of the WCC si ble ex pla na tion is that the Ju ras sic units (at least the (quartz diorite and granodiorite) and medium - and coarse- WCC) are folded along doubly plunging axes (both north - grained granodiorite to monzonite were sam pled from the west and southeas t) that conver ge to form a dome structure Island Plutonic suite. Major and minor el em ents were de - somewhere be tween Twin Lakes and Browns moun tain. ter mined for am phibole and plagioclase using a CAMECA The loca ti on where the fold axis changes plunge from SX50 elec tron microprobe at The Univer sity of Brit ish Co - north west to south east con tains the high est con cen tra tion lum bia. Op er at ing con di tions were 15 kV ac cel er a tion volt - of ultram afic rocks. Thus, the WCC, the Island Plutonic age at a beam current of 20.1 nA and count ing times of 20 s suite and the Bo nanza Group in the field area are all part of a on peaks. Stan dards in cluded nat u ral ol iv ine, di op side, an- larger fold struc ture plunging with fold axes in the north - or thite, al bite, orthoclase, kaersutite, rutile and faya lite. In west and southeas t di recti ons, exposing varying structural each sam ple, from four to ten grains each of am phibole and depth. plagioclase were measured , with analyses of both cores and rims on each grain.
Near Har ris Creek, a large area of Karmutsen basalt is jux - The alu mi num-in-hornblende ba rom e ter (PHbl) was ap plied taposed with the WCC diorite along a 10 m thick shear zone to rocks contai ning quartz to buffer silica acti vit y and with with the same atti tude as the per va sive fo li a tion in the hornblendes having Mg/Mg+Fe >0.35 (Ander son and diorite. The shear zone is well exposed along the Harris Smith, 1995). Where plagioclase was fresh, the Creek and southern Hemmingsen mainli nes. Less obvi ous hornblende–plagioclase geothermometer (Holland and shear zones are defined by centim etre- to metre-thick my - Blundy, 1994) was appli ed to esti mate tem pera ture . For the lonit e hori zons in the more western parts of the field area, sam ples, a alu mi num-in-hornblende ba rom e ter for mu la- within the WCC diorite near Camper Creek and Twin tion is appli ed that ac counts for the ef fects of tem pera ture Lakes. These faults are express ed on topo graphi c and aero- THB on the Al content of hornblende using THB (Anderson magnet ic maps in the southwest portion of the map area. and Smith, 1995).
Geoscience BC Re port 2010-1 145 This study, which was extende d for Juras sic plutons across much of Vancou ver Island (Canil et al., in press), con sis tently shows the high est crys tal li za tion depths in WCC plutons (10–18 km; Figure 6), support ing the noti on that this unit repre sent s the deepest lev els of the Bo nanza Arc (DeBari et al., 1999). The WCC is well exposed in southern - most Vancou ver Island in the Victo ria area (Figure 6) and in the Port Renfrew area ex - tending along the west coast of Vancou ver Is- land. If the San Juan fault is consid ered a strike-slip fault, the resto ra ti on of ~80 km of sinistral movem ent along this fault brings the depths recorded in the WCC in the Vic to ria area in line with those in Port Renfrew (13 km) and Gold River (12 km), suggest ing these plutons were once conti nu ous along strike. If so, the San Juan fault must be youn- ger than the Bonanza Arc (170 Ma) and older than the maxi m um age of the Nanaimo Group (93 Ma; Mustar d, 1994), becaus e sedi m entar y rocks of the latter are not offset by this fault. Con sid er ing any dip-slip com po nent in this fault will reduce the estimate of strike-slip movement. On southern Vancou ver Island, five sam ples of the Is land Plutonic suite all crys tal lized at depths of approx i m ately 4–5 km but are too sparsely distri buted to reveal any regional struc tural infor m ati on along a transect norm al to re gional strike from Port Renfrew in the west to Ladysmith in the east. The depths of Fig ure 5. Vancou ver Is land, Brit ish Co lum bia, showing only the major regional expo sure from this study for plutons on south- struc tures and ge ol ogy of the Juras sic Bo nanza Arc, sub di vided into Bo nanza vol - ca nic rocks, Is land Plutonic suite and Westcoast Cryst al line Com plex: a) Sample ern Vancou ver Island suggest this suite must lo ca tions for hornblende ba rome try (this study); b) As above but showing depth of exist as num erous thin, tabu lar bodies to fit crys tal li za tion of plutons from alu mi num-in-hornblende ba rom e try (as sum ing within the stratigraphically measur ed thick - 100 MPa = 3 km depth). Not all bar o met ric re sults are shown for clar ity. nesses of pre-Juras sic supracrustal rocks on Wrangellia (Figure 6). When com paring PHbl with strati - and Trias sic supracrustal rocks, likely in the middle and graphic secti ons for Wrangellia, the result s are not support - lower crust below them (Figure 6). ive of previ ous inter preta ti ons (Yorath et al., 1985) that Pa- leo zoic and Me so zoic strata of Wrangellia are ‘roof Economic Geology pendants ’ perched on an under ly ing Juras sic plutonic com - plex. To fit the depths from hornblende barom etry and map Assay s of the ultram afic rocks returne d gener all y low val - patter ns, the Juras sic arc intru sions must be tabu lar and in- ues of Au, Pt and Pd (1–7 ppb). This is not surpris ing given trude within the strati gra phy of the older units of Wran- the low amounts of sulphide in the sam ples. Ultram afic gellia, which can be mapped as septa within the intru sions . rocks oc cur in several geolog i cal set tings. The ultram afic cumulates in the WCC around the Port Renfrew area are in - con sis tent with an ophiolite as so ci a tion or ‘Alas kan-type’ There are fewer con straints on the Wrangellia stratig ra phy intru sion (Larocque and Canil, 2007) into which the lesser sam pled and more mafic WCC in - truded. The few depth constra ints for crystal li zati on sug- Peridotite and pyroxenite bodies with identi cal petro- gest that unli ke the more evolved granit ic Island Plutonic graphic and geolog i cal rela ti onships are noted to oc cur to - suite, this mafic-ultra mafic unit in truded depths greater wards the middle and base of crust in exhum ed is land arc than any measured strati graphic thicknesse s of Devo nian ter ranes. Such an inter preta ti on for these rocks in the Port
146 Geoscience BC Sum mary of Ac tiv i ties 2009 Renfrew area is comm en su rate with their thermobarometry veal the conti nuit y betwee n these or other surface ultra- (Canil et al., in press; Larocque and Canil, 2009). The Bo- mafic bod ies at depth beneath the area. nanza Arc and its setti ng on Vancou ver Island are very sim - ilar to the Talkeetna Arc in south-centra l Alaska, and it has No sig nif i cant con cen tra tions of chro mite, sulphides or been proposed that the two are of sim ilar age and can be plat inum -group miner als were noted in the ultram afic rocks cor re lated along strike (DeBari et al., 1999). in out crop, hand sam ple or thin sec tion. Only minor amounts (<2%) of Cu- and Ni-sulphides (chalco py rit e, Future Work pentlandite, pyrrhotite) or chrom ite are seen in thin secti on. For this rea son, and in view of the discon ti nu ous expo sure The major it y of the ultram afic bodies in the Port Renfrew of the ultram afic rocks, heavy-min eral stream sam pling is area are discon ti nu ous and tend to be distri buted in patches not likely to be an ef fecti ve method for uncov er ing further through out the WCC. Ar eas of sig nif i cant con cen tra tion occurrences of these rocks. are on Fairy mountai n and along the Granit e Creek main- line. Ar eas of the WCC that host ultra mafic rocks appear to Mag ne tite skarn bod ies, if of sig nif i cant eco nomic in ter est, corre spond with magneti c highs in both the regional and may be de tected near the sur face by magnetic sur veys, de tailed aero mag net ic sur veys. The aero mag net ic highs looking for a contra st of units with weak magne ti sm (mar- may also cor re spond with lat er ally dis con tin u ous mag ne- ble) ad ja cent to strong mag ne tism (mag ne tite). Be cause the tite skarn, which are strongly magneti c in out crop. Becaus e marble bodies appear to have some structura l conti nuit y nei ther of the latter rock types is spe cif ically asso ciated (Fig ures 4, 5), ar eas for de tailed sur vey are best ac com- with ultram afic rocks, further detai led magneti c surveys in plished along strike of exist ing magne ti te bodies . The Ju - the field area will not be exclusive to the detection of rassic rock units are folded, however , and it is possi ble that ultramafic rocks. the magne ti te skarn bodies plunge with depth along the re- gional fold axes, explai ning why they are not observe d con- If the regional magneti c signal is control led by the presence tinu ously along strike in out crop at the surface . Further de- of ultram afic rocks, there may be a signif i cant amount of linea ti on at depth of the exist ing magne ti te bodies might be these rocks hidden at depth within the WCC. Geo phys i cal located by drilling orthogonal to the plunge of regional in ves ti ga tions (de tailed grav ity sur vey) or drill ing may re- folds.
Fig ure 6. Sec tions for Wrangellia on Vancou ver Is land, Brit ish Co lum bia, drawn to accom mo date the mea sured strati graphic thick nesses for Bo nanza vol ca nic rocks and pre-Juras sic supracrustal rocks of the Vancou ver and Sicker groups (left-hand panel) with the depths of crys tal li za tion from hornblende ba rome try of plutons from the Is land Plutonic suite and the Westcoast Cryst al line Com plex (Canil et al., in press) and ultra mafic cumulates (Larocque, 2008). The right-hand panel shows how the range of hornblende pres sures can be ac com mo dated in the sec tion by having the Is land Plutonic suite in trude as sev eral thin ner tabu lar bod ies through out the pre-Ju- ras sic stratig raphy , and with plutons of the Westcoast Crys tal line Com plex emplaced be low both of the latter .
Geoscience BC Re port 2010-1 147 Acknowledgments ther mom e try; Con tri bu tions to Min er al ogy and Pe trol ogy, v. 116, p. 433–447. First and forem ost, the author thanks P. Heatherington and Larocque, J. (2008): The role of amphi bole in the evo lu tion of arc G. Pearson in Port Renfrew for their support, assis tance and magmas and crust: the case from the Juras sic Bo nanza Arc sec tion, Van cou ver Is land, Can ada; M.Sc. The sis, Uni ver - gener os it y in this project . J. Larocque carrie d out the major - sity of Vic to ria, 160 p. ity of this pro ject for his M.Sc. the sis. As sis tance for var i - Larocque, J. and Canil, D. (2007): Ultra mafic rock oc cur rences in ous aspect s of the project was provided by R. Friedm an, the Ju ras sic Bo nanza Arc near Port Renfrew (NTS 092C/09, H. Steenkamp, E. Bonnet, J. Kyba, J. Styan and O. Canil. 10, 15, 16), south ern Van cou ver Is land; in Geo log i cal Field- The author thanks N. Massey, G. Nixon, L. Coogan, work 2006, BC Min istry of En ergy, Mines and Pe tro leum A. Hynes, S. DeBari, S. Johnston and P. Luffi for their criti - Re sources, Pa per 2007-1 and Geoscience BC, Re port 2007- cism, com ments, reviews or input at various stages. 1, p. 319–324. Larocque, J. and Canil, D. (2009): The role of am phi bole in the evo lu tion of arc mag mas and crust: the case from the Juras - References sic Bo nanza Arc sec tion, Van cou ver Is land, Can ada; Con tri - bu tions to Min er al ogy and Pe trol ogy, doi:10.1007/s00410- Ander son, J.L. and Smith, D.R. (1995): The ef fects of tem per a ture 009-0436-z. and fO2 on the Al-in-hornblende ba rome ter; Amer i can Min - er al ogist, v. 80, p. 549–559. Mul ler, J.E. (1983): Ge ol ogy of Vic to ria; Geo log i cal Sur vey of Can ada, Map 1553A, scale 1:100 000. BC Geo log i cal Sur vey (2009): MapPlace GIS internet map ping Mustard, P.J. (1994): The Upper Cre ta ceous Nanaimo Group, system; BC Min istry of En ergy, Mines and Pe tro leum Re - Geor gia Ba sin, in Monger , J.H. (ed.), Geo log i cal Haz ards of sources, MapPlace website, URL
148 Geoscience BC Sum mary of Ac tiv i ties 2009