Metallogenesis and Tectonics of the Russian Far East, Alaska, and ...

along the western end in the Eagle Zone; (2) scheelite-quartz veins in the east-centml part; and (3) Au-sulfide quartz veins along
the nort hem contact and to the west. The associated Ray Gulch (him) W skam deposit occurs on the south side of the Dublin
Gulch stock, and casslterlte breccia deposits occur 2 km north of the stock. The Au quartz veins in the Eagl~ Zom mgt £rom I to
2 cm wide, and are associated with potassic and phyllic envelopes which coalesce to form pervasive alteration which wfBiD. the
closely-spaced quartz veins. Vein mineral assemblages, in addition to free gold grabs up to 1 mm in diameter, are gmenowpik,
pyrrhotite, chalcopyrite, pyrite, bismuthinite, tetradymite, teIlwbimuthiaife, native bismuth, and rare moIyWenite md 5elite.
Estimated resources are 64.5 million tonnes mdiag 1.03 g/t Au (Hkbhins and Otasicb, 19%).
Ray Gulch W Skarn Deposit
The Ray Gulch W skarn deposit consists of scheelite which occurs as disseminations ad tabda layea in $u#kle&ee
diopside-amphibole-epidote skm. The deposit is hosted in calcmus mebsedhentary rocks and €@ofthe l.,&eProterou,Ec
Hyland Group which is intruded by quartz monzonite sills which dip gently northward towards the FortWo Hi18 StOLIk, wof fbe
mid-Cretaceous Tombstone Plutonic Suite. Eight separate skarn zones comprise a resource of5.44 million tomes of mtezid
grading 0.82% W03 (Lennm, 1986). Other W skm are at Scheeiite Dm, Lugdush, and abosgobel. Sa skaragwur in the
Keno Hill-McQuesten River region, and include Oliver Creek, Boulder Creek, East Ridge, md B%mey Ridge. Also occuhhg in
the area are several veln and breccia Sn-W deposits which are ho&cd by Late Protmie to Mississippian imW&nWq todrs
and associated felslc granll~id stocks of he Tombstams Phltmk Suite (EmaJbd id L,ynch, 19921, S
occur at Marn, Brenner, and Ida.
d a-Au depaita
Origin of and Tectonic Controls for
Tombstone Metallogenic belt
The Tombstone matallogcok ball in bat& in the mid-Cretaceous Tombstone Plutonic Sub wlmicb intrudes tse PtotPd~
Hyland and Cambrian through Devonhn Rocky Mountain Adage, and the Devonian and Missis8ippian c W we&e roChLp
of Earn Group of the North Americrcn htoo Mqpn (tig. 62). The Tombstone Plutonic Suite, wbicb has isotopic aga of9549
Ma, consists mainly of alkaline pluloras which include sycnib, hornblende-biotite granodiorite, quartz mmQnite, aad qmabfeldspar
porphyry. The plutonic suite includas xmre kleic, paahminous, tyvo-mica granite and quark d t e plwws whicfi
were previously included in the a6ghtly older Sdwyn Flutoak St& which has isotopic ages of 97 to 112 Ma Tbe grmitokl rods
of the Tombstone Plutonic Suik, which are part of bw-Selwyn plutonic suite, are simh in age, geocbmkfry, and
petrology to mid-Cretaceous flutons which iphude Ibe Y b T terrm ~ to the west in Alaalra ~ Q Stha-hdi S fault, md
the suites of lode deposits assocW with each suite of lpanitoid mh are sbnilar. The T~tonc ~ o pbblt k mbbs Ag
polymetallic vein, gramtoid-telela8 Au, SbAn vein, W-Sn-Au skam, and Cu-Au skam depaits. The o k (mid-Gretatxous) plart of
the East-Central Alaska metallogenic belt contains granitoid-related Ay Sb-Au vein, Pb-Ag-Zn-Au poJymebllic vvein, d W-AU
skarn deposits. In recent yeas, the name Tinh)ra G;oldi?eit (Tucker and Smith, 2000) has bem used for gmaitoid-related Au
deposits and occurrences which occur throughout the Yukon Territory d in &G East-Central Ahda xmhdkgenic belt (described
below) of Nokleberg and otbers (1995a, 1996, I997sr), and m the comedative TainWne metdogenie bt1t of Meberg and
others (1995a, 1996, 1997a) which occm to the oast in the ~~ Yukon Tmritory. Because the term TlatiM GohJ E d includes
deposits of several ages and Merelling origins, the term is not wmd in t4isstudy. Bundtzen and ot.hm (2W) inwoducexl the tan
Tintina Gold Province to denote Mesozoic and T&hy plutonic-related gold &posits which rn &Ead to which owxir b~~ghOllt
the Yukon Territory and lrderior Alaska.
As described aboe fw the correlative East-Central Alasktl mdlogenic belt (mid-Cww), the polym6taflic, SbAu
vein, and granitoid-related Au deposits of the Tombstone metallogenic belt are generally hosted in, ar nearmid-Cxetaceous
granitoid plutons (Nokleberg andothers, 199%; McCoy and others, 1997; Smith, 1999; Smith aMf 9tbas, 1999, 2 W 1 @ki&b
and others, 2000). In both Jiut-Central Alaska and the Central Yukon Territory, Ihe phkw are iuhxpreted as thing
the waning stages of a major mid-Cretaceous collision of the Wrangellirm supatemane with the ~ ously~crered Yukon-Tanma
terrane (Stanley and ohers, 1990; hrsel Bacon and others, 1993; Pavlis and others, 1993; NoUebctg and others, 2000). ']The
collision a& aa~ociared rnehmorphiun and deformation is interpreted as forming in two phases: (I) a relatively alder parid of
collision axid thrusting, assDcirted wi(h high-temperatun and high-pm metamarpbm, and (2) a slightly younger mod of
extension asswiatcd with lower greawhist hies metamorphism. The mid-Cretaceous gmitoid rocks md relalively ymmge~
quartz veins intiude and cmsscut bath the relatively older, lugher-grade, aad relatively younger, lower gtwb metmwpbie Eabrics
in the region (Dusel Bacon asld others, 1993; Pavlis and others, 1993) These relations suggest that the the Tphtone
metallogenic belt formed in rhe wantog stages of this complex d d i b n event (Noklekg, 1997e, 2 0 . Mher mWo@c
belts of granitic-magmatismrtld deposits haetod in the Ombm-mn plufodc belt in the Camdim C&M, Alllasks, and tb
Russian Northeast include the Bayome, C&u, Selwp, and Whiteha beh (fig. 62; table 3).