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- grenville orogeny: Grenville orogeny

- Mesoproterozoic: Mesoproterozoic

- Migmatite: Migmatite

- Monazite: Monazite

Because of continental drift these collided with Laurentia (the precursor of modern North America) in a mountain building episode known as the Grenville orogeny.

Adirondack Mountains#Geology

Geology of New England:

Archean and Proterozoic eons[edit]

In the Archean Eon Western Massachusetts and Vermont were the eastern edge of Laurentia (now the Canadian Shield). Laurentia is believed to have originated at the end of the Hadean, making it one of the oldest regions with continental crust, as evidenced by the discovery of Acasta Gneiss in Canada. At the end of the Hadean massive eruptions of felsic lava became cool enough to form permanent crust. The felsic nature of Laurentia allowed it to float over the denser ocean basins that surrounded it, so it was not submerged under the then-forming oceans. During the Archean Eon the surface of New England was a coastal desert covered by silica-rich sediments with outcroppings of granite bedrock.

New Paragraph:

In the Mesoproterozoic eon, an important mountain building episode which aided in the assembly of the supercontinent Rodinia, the Grenville orogeny, occurred. The result of this event are still evident today in the Adirondack Mountains.

Adirondack Mountains:

[here what is bolded is changed]

The rocks of the Adirondack mountains originated about two billion years ago as 50,000 feet (15,000 m) thick sediments at the bottom of a sea located near the equator. Because of continental drift these collided with Laurentia(the precursor of modern North America) in a mountain building episode known as the Grenville orogeny, which occurred between 1250-980 Ma. These dates were determined through the use of Monazite geochronology. During this time the sedimentary rock was changed into metamorphic rock. There is also a presence of migmatites which are rocks that are a combination of metamorphic and igneous rocks which formed as a result of partial melting. They were formed in the Shawinigan (1190-1160 Ma) and Ottowan (1090-1050) subsets of the Grenville Orogeny. It is these Proterozoic minerals and lithologies that make up the core of the massif. Minerals of interest include:

• wollastonite, mined near Harrisville
• magnetite and hematite, formerly mined at the Benson Mines, Lyon Mountain, Mineville, Tawahus, and Witherbee.
• graphite, mined near Hague and Ticonderoga.
• garnet, mined at the Barton Mine, north of Gore Mountain.
• anorthosite, visible in road cuts on the New York State Route 3 between Saranac Lake and Tupper Lake.
• marble
• titanium was mined at Tawahus.

Authors for our field Trip:

Source:

Williams, Michael L., Grover, Timothy W., Pless, Claire R., Suarez, Kaitlyn A., Regan, Sean P., Baird, Graham B., 2018, Migmatites of the Eastern Adirondack Mountains: New Constraints On the Timing, Petrology, and Tectonic Setting of Partial Melting in Grove, Tim and Mango, Helen (editors), Guidebook for field trips in New York and Vermont: New England Intercollegiate Geological Conference, 110th Annual Meeting and New York State Geological Association, 90^th Annual Meeting, October 12-14, 2018, Lake George, N.Y., 301 p, color.