USGS Professional Paper 1697 - Alaska Resources Library

groups of deposits are interpreted as forming during assimilation
of the continental, Late Proterozoic and early and middle
Paleozoic metasedimentary rocks of the Seward metamorphosed
continental-margin terrane (Hudson and Arth, 1983;
Swanson and others, 1988). Alternatively, on the basis of
Map
150
W
Cassiterite
Creek
Cross section
W
120
0 120 m
Cassiterite
Creek
Cassiterite Creek
120
Cassiterite Dike No 3 Adit
Late Cretaceous and Early Tertiary Metallogenic Belts (84 to 52 Ma) (figs. 102, 103) 225
90
120
150
150
No 1 Adit
210
E
180
trace element data, the Sn granite and related deposits are
interpreted as forming during crustal extension (Newberry and
others, 1997b).
On the basis of similar geochemistry, age, and spatial
proximity, the host Late Cretaceous granitic rocks on the
E
Zone of vein density 5-10%;
dominantly fluorite-white mica veins
Zone of vein density 10-30%;
fluorite-white mica veins
Zone of vein density 10-30%;
abundant hydrous skarn
Zone of veindensity >30%;
most early skarn and abundant
hydrous skarn
Clay-matrix breccia
Muscovite-matrix breccia
Muscovite-quartz-tourmaline greisen
Quartz-topaz-tourmaline greisen
Quartz porphyry dike
Leucogranite
Diabase dike
Ordovician carbonate rocks
Normal fault
Contact
Figure 107. Lost River Sn-W skarn and Sn greisen deposit, Seward Peninsula metallogenic belt, Seward Peninsula,
Alaska. Schematic geologic map and cross section. Adapted from Dobson (1982) and Hudson and Reed (1997).
See figure 103 and table 4 for location.