Geology of the Adirondack Mountains (cont.)
Adirondack Highlands (cont.)
4.3 Miscellaneous rocks
Figure 4-18. Folded marble and calcsilicate east of Speculator.
The protoliths of these metamorphic rocks were more or less impure limestone and dolostone deposited as shelf sediments in the Trans-Adirondack basin.
Figure 4-19. Calcsilicate and granite south of Tupper Lake.
Diopside-rich calcsilicates (see origin with preceding figure) intruded by granite and interlayered with white pegmatite. During metamorphism, diopside forms from the Ca-rich limestone and dolostone. Diopside gives calcsilicate its green color. Granite and pegmatite probably belong to the AMCG suite.
Figure 4-20. Calcsilicate and granite south of Tupper Lake: close-up.
Figure 4-21. Lyons Falls.
Black River's Lyons Falls, near the town of the same name, have been harnessed by a power plant. The falls correspond to an erosion-resistant amphibolite gneiss.
Figure 4-22. Lyons Falls amphibolite gneiss.
Close-up of Lyons Falls' two-pyroxene amphibolite gneiss with plagioclase bands. Quarter for scale.
Figure 4-23. Agers Falls on the Moose River, east of Lyons Falls.
The Moose River here flows over a leucogranite, dated at 1035 Ma by by McLelland et al. (2002) and considered by these authors as a late occurrence of Lyon Mountain granite (1050 Ma in the northern Highlands).
Figure 4-24. Agers Falls leucogranite with quartz-sillimanite segregations.
The boudinaged and ruptured segregations (nodules) were formed during the granite intrusion by hydrothermal leaching of the calcsilicate country rock (McLelland et al., 2002). Quarter for scale.
Figure 4-25. Agers Falls leucogranite with pegmatite veins.
Calcsilicate country rock appears as darker than leucogranite. Pegmatite veins, dated at 1034 Ma (McLelland et al., 2002) crosscut the slightly younger quartz-sillimanite nodules.
Acknowledgements: the field trips during which these photos were taken were made possible thanks to the articles by Darling (2012), Florence et al. (1997), McLelland (1992, 2003), and Orrell et al. (2000).