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

A theoretical example of rbe first steps of the methodology for the metallogenic and tectonic analysis is provided in
figure 1. Figure 1A illustrates a theoretical suite of metallogenic belts which are hosted in several geologic unils cratons, terranes,
and overlq assemblages, or along major faults between terranes. Figure 1B illustrates the stratigraphic and metallogenic hislory of
the map area. The steps in this theoretical example are as follows. (1) Key terms are defined or cited from previous studies (e.g.,
Naklebug end others, 1997a). (2) A regional geologic base map is constructed which illustrates two major cratoas (A, B), seven1
fault-bounded terranes (i, 2,3,4), one accretionary assemblage (a), and four post-accretion overlap assemblages (b, c, d, e). (3) A
series of mineral deposit models are defined and described, and a high-quality mineral deposit data base is compiled. For this
theoretical example, the mupr mineral deposit types are low-sulfide Au quartz vein, ironstone, epithermal Au vein, porphyry Cu,
bded barite, and kuroko massive sulfide. (4) Metallogenic belts are delineated. For simplicity i.n this example, each metallogenic
belt containa only a single mineral deposit type. 'The two cratons (A, B) each contain distinctive, pre-accretionary meleOogenic
belts (ironstone and bedded barite deposits) which formed early in their geologic history, and an island asc assmblaga (terrae 4)
contains a pre-accretionary mctaUogenic belt of kuroko massive sulfide deposits. A collisiond granitic pluton with a porphyry Cu
mttallogenic belt formed during accretion of terrane 3 against terrane 4. A metallogenic bell containing Au quartz vein deposits
formed during accretion of terrme 1 against terrane 2. Overlying all terranes and both cratons is a post-accreliw overhp
assemblage which contains a rnetallogenic belt of epithexmal Au vein deposits. (5) The genesis of formation of bedrock geologic
mits and {or) structures and contained mineral resource tract or metallogenic belt is interpreted using modem lectonic cancepts
(fig. IB). Examplee include: kuroko massive sulfide deposits forming in an island arc environment; porphyry Cu and bw-sulfide
Au quartz vein deposits forming in an accretionary environment, and epithermal Au vein deposits fomhg in a continental-margin
igneous-arc environment. And (6) by carefully defining each metallogenic belt to be the geologically-favorable area for a group of
coeval and genetically-related mineral deposits, a predictive character is established within the beb for undiscovered deposits.
Henca, regional metallogenic analysis should be valuable for mineral exploration, land-use planniag, and environmental studies,
A. hAap V iw d Orogenic Belt
VERLAP
E ilherrnal Au Vein
(8 ost-Accretionary)
1
8. Strattgraphk Columns for
Orogenic Be&
F~UR 1. Generalbed theoretical example illustrating the methodology for metallogenic analysis of cratons, ter-, tw3em
aSembhgeS, overlap assemblages, and contained metallogenic belts. A. Map view example of omgenic beR. 8. Stfatigraphic
columns for example oragenic belt. Refer to text for discussion.
Tectonic Controls for Metallogenesis
Interpretation of the coqrehensive data base of mineral deposits (Nokleberg and others, 1997a), mineral-resome tract
maps (Weberg and others, 1997b, 1998), terrane and overlap assemblage maps (Nokleberg and others, 1997c, 1998), and the
companion rnetallogenic and tectonie rnodel for the Russian Far East, Alaska, and the Canadian Cordillem, f tjvd seven major
tectonic environments for tbe Phanerozoic metallogenesis of the region: (1) subduction-related arc; (2) coUki0d (anatectie)
related arc; (3) post-collisional extension; (4) oceanic rift; (5) continental rift; (6) back-arc rift; and (7) transform continental-
margin arc. Each teclomc environment provides a unique interpretation for the origin of the 144 major metallogenic belts and