Petrology, GEO-320 – Kurt Hollocher

Petrology is the study of rocks, their composition, mineralogy, and origin. The detailed characteristics of chemistry, minerals, and mineral textures can lead to a detailed understanding of rock genesis. This information can then be used to address larger scale geologic issues, such as the tectonic development of mountain ranges and the eruptive history of volcanoes.

Special documents	Syllabus
	Using petrographic microscopes: adjustments and features
	Internet resources
	Exam study guides	Igneous rocks Metamorphic rocks
Igneous rock labs	White Mountain magma series	WMMS data set WMMS discussions 1, 2, 3 Photo gallery
	New Hampshire magma series	NHMS and Wooley Creek data sets NHMS discussions 1, 2, 3 Photo gallery
	Skaergaard and Stillwater intrusions	Skaergaard topics 1, 2, 3 Stillwater topics 1, 2, 3 Skaergaard photo gallery 1, 2. Stillwater photo gallery 1.
	Iceland lavas	Iceland lavas data set Iceland geology and discussions 1, 2, 3 Photo gallery
Metamorphic rock labs	New England schists	New England geology 1, 2; metamorphism 1, 2 New England schist discussions 1, 2 Photo gallery
	New England mafic rocks	New England geology 1, 2; metamorphism 1, 2 New England mafic discussions 1, 2, 3 Photo gallery
	Norwegian eclogites	Fennoscandia geologic map, very simplified map Geologic discussions 1, 2, 3 Photo gallery
	Fault rocks	Fault rock discussions 1, 2 Photo gallery
Forms and graph paper	Rock report form Ternary graph paper, and a green one
Documents and spreadsheet utilities	Writing igneous rock hand sample descriptions Writing metamorphic rock hand sample descriptions Papers to replace field trips Why petrology is so much fun
	How to calculate norms from rock chemical analyses NORM4 norm spreadsheet for single samples NORM4 macro-enabled version for multiple samples (file type not allowed here, ask me for a copy)
	Estimating Fe³⁺ in amphiboles Estimating Fe³⁺ in biotite Making thin sections Staining feldspars in thin section
	Fill in missing values on REE diagrams! Make ternary (triangle) diagrams in spreadsheets! Whole rock geochemical discriminant diagrams!
Image libraries	Igneous minerals in thin section Igneous textures in thin section Metamorphic minerals in thin section Metamorphic reactions in thin section Metamorphic microstructures in thin section Moon rocks Hand sketches in petrology
SVG vector graphics files for figures I use in this course (native Inkscape)

Assorted field trip images

Feeling for fault movement indicators on a slickensided surface, Waloomsac Formation, Rt. 8, North Adams, Massachusetts.
Graded quartzite beds in Littleton Formation schist. Person is standing on the axial surface of an isoclinal fold that repeats the bed, upside down in front and right side up behind.
The largest plagioclase crystal found in this trip, larger than a size 12 boot.
Natural Bridge, in Natural Bridge State Park, North Adams, MA.
View to the southwest, overlooking Monta Rosa.
Folded marble, West Stockbridge Formation, Natural Bridge Park, North Adams, Massachusetts. Photo donated by Ralf Schauer.
Summit of Monadnock.
Marble-matrix breccia near Paradox.
Black Precipice for lunch.
Deformed xenolith breccia in gabbroic rocks, as part of the older plutonic complex in the roots of the Taconian island arc. Shelburne Falls.
Large twinned plagioclase, summit of Mt. Jo, in an anorthosite block within the leuconorite.
The two notches in the outcrop are weathered out alkali basalt (camptonite?) dikes cutting leuconorite, near the summit of Mt. Jo.
Salamander escapes from tent caterpillar.
Magnetite ore body and mine west of Ticonderoga, NY.
Brian pops out of the boulder cave.
Even more lunch.
Portrait of an unhappy snake.
Late quartz vein with 25 cm wide tourmalinized zone around the vein.
Lunch on Black Precipice, looking south at the landscape.
Chicken track pattern of andalumps on a foliation surface.
Nice graded quartzite bed. Top is to the upper left.
Large plagioclase megacryst in anorthosite, Mt. Jo.
Looking down on Heart Lake, adjacent to the Adirondack Loj campground.
Reaching the top of Mt. Jo, high peaks in the distance.
Largest plagioclase megacryst in anorthosite, Mt. Jo.
Late fault offsetting quartzite layer.
View from the summit to the south, toward Bald Rock (left) and the halfway house site (right).
Large plagioclase crystal in Mt. Marcy-type anorthosite, Mt. Jo, short trail up.
If you are going to take a snooze, it might as well be in a nice spot!
Looking for graphite in marble, Warrensburg, NY.
Tonalitic gneisses and amphibolites at the Shelburne Falls, Shelburne Falls, Massachusetts.
Summit of Mt. Jo.
Boulder cave exit.
Group photo from Pine Cobble, Williamstown, Massachusetts. Stop 4 at 9:00 AM.
The true breakfast, lunch, and dinner of champions.
Outcrop of Clough Quartzite on Crag Mountain, Erving, Massachusetts. View to south-southeast toward the Northfield Mountain pumped storage reservoir in the Pelham Dome.
Metamorphosed limestone of the West Stockbridge Formation, North Adams, Massachusetts.
Same as above, with Mike and Bill for scale.
Anna pops out of the boulder cave.
Boulder cave exit, again.
Folded quartzite beds.
Bill reading the paper.
Large metamorphic garnets in an amphibolite.
Ferrosyentie dike cutting leuconorite, summit of Mt. Jo.
Graded quartzite bed, stratigraphic top to the upper right.
Large tourmaline crystals in a quartz vein. Largest crystal is ~5 cm long.
More isoclinally folded quartzite beds.
Large garnets in melt pockets in an amphibolite.
The Fairy at Fairy Spring, on the Fairy Spring trail to Monta Rosa.
Coarse-grained, intensely folded graphite- and diopside-bearing marble on the shores of the Hudson River, Warrensburg, NY.
Summit of Monadnock.
Eroded lamprophyre dike, near the summit of Mt. Jo.
“Billings Fold” near the Monadnock summit.
Eroded lamprophyre dike, near the summit of Mt. Jo.
Another group photo at Pine Cobble, Williamstown, Massachusetts. Stop 4 at 9:00 AM. Photo donated by Ralf Schauer.
Normal-size samples are sufficient for normal people.
Summit of Mt. Jo.
Bill, hanging up.
Woodchuck on Jurassic red bed sediments, Turners Falls, MA.
Rainwater pool off the main trail, looking southeast toward Bald Rock.
Big garnet outcrop, Warrensburg, NY.
Isoclinally folded quartzite beds.
David pops out of the boulder cave.
On the hike down we found another part of the Billings Fold, ~200 m along the axial surface.
Praying for divine guidance: what is that soft, flakey, metallic mineral in this marble?
Hornblende needles in muscovite-biotite-chlorite-garnet schist.
Samples of magnetite-garnet sand, Schroon River.
Large xenolith choking the interior of a thin tourmaline granite sill.
The “Billings Fold”, a large isoclinal syncline just below and southwest of the Monadnock summit.
Coming down from the summit. It’s actually not as steep as it looks.
Halfway house site, with andalump schist and pegmatite.
Mylonite zone cutting gabbroic anorthosite, Keene Valley.
Large tourmaline crystals in a quartz vein. Longest crystal is ~4 cm.
Hornblende-diopside-plagioclase-calcite vein in an amphibolite ‘xenolith’ in the deformed marble, banks of the Hudson River.
Well, it beats PB and J again.
Off the main trail, looking toward the summit.
Large plagioclase crystal in a block of anorthosite within the leuconorite, summit of Mt. Jo.
Paying homage to partially recrystallized (Whiteface Mtn. type) anorthosite.
Fold hinge in one of the isoclinally folded quartzite beds.
Trying to get out to the outcrop in the middle of the river, Jay.
Summit of Mt. Jo.
Labradorite showing labradorescence. It is caused by a diffraction effect from closely-spaced exsolution lamellae.
Looking at metamorphosed quartz pebble conglomerate in the Cheshire Quartzite, Pine Cobble Trail, Williamstown, MA.
Approaching the summit region.
Patrick pops out of the boulder cave.
Highly deformed marble on the shores of the Hudson River.
Nick eating the finest peanut butter sandwich in New Hampshire.
Looking at a thin ferrogabbro dike crosscutting anorthosite.
Cambrian Cheshire quartzite on Pine Cobble, Williamstown, Massachusetts.
Petrology, 2000. Sarah, Nick, Mike, Bill, Sarah, Jeremy on the summit.
Looking at metamorphosed quartz pebble conglomerate in the Cheshire Quartzite, Pine Cobble Trail, Williamstown, MA.
Checking out an especially large muscovite crystal in a pegmatite dike.
Looking southwest from the top of Roaring Brook falls, Giant Mountain, Adirondacks.
Boulder cave entrance.
Exposures of the Roaring Brook intrusion breccia, Giant Mountain, Adirondacks.
Nick and Bill hanging out.
Charnockite gneiss near Schroon Lake.
Deformed marble with numerous ‘xenolith’ blocks and folded layers, Paradox.
Nice red garnets. The schists contain red garnets up to 2 cm across.
Contact between a granitic gneiss (light colored center and right) and a garnet amphibolite (lower left).
Summit of Monadnock.
Blue calcite!
Crossing Roaring Brook on the way to some outcrops, Giant Mountain, Adirondacks.
Pre-hike lunch making. Nothing better than peanut butter and jelly!
Searching for mega-samples, as usual.
Coarse-grained marble on the shores of the Hudson River.
A new friend.
Early risers in Petrology, 2004.
More lunch on Black Precipice.
Salamander rushes off at top speed.
“Billings Fold” just below the summit.
Small fault with calcite infilling, cutting calc-silicate block in marble, Paradox.
And snacks, too!
Eroded lamprophyre dike, near the summit of Mt. Jo.
Coticule layer near the Billings Fold.
Looking back toward the summit from Bald Rock, on the way to the graphite mine and the boulder cave.
Infold of marble and calc-silicate layers into a partially separated amphibolite boudin neck, banks of the Hudson River.
Silurian Clough quartzite, Crag Mountain, just west of the Connecticut River valley.
Looking at a quartz-pebble conglomerate in the Cheshire Quartzite, about half way up the trail to Pine Cobble, Williamstown.
Folded calc-silicate layer in marble, banks of the Hudson River.
Metamorphosed tonalitic intrusives of the Taconian arc complex, Shelburne Falls, MA.
Searching for blue calcite, cascade slide.
Off the trail looking at complex isoclinal folds and graded quartzite beds.
Layer truncations against a thick quartzite. Possible pre-metamorphic sedimentary structures, or a fault surface.
Lunch on Black Precipice, sitting on the “Seven Sisters” quartzite beds.
Large quartz mass in the neck between two large amphibolite boudins in marble, Paradox.
View to the east from the summit. Boston was not visible today.
Alkali basalt dike cutting leuconorite, on the long trail down from the summit of Mt. Jo.
More folded quartzite beds. Wind is gusting to 50 mph.
Summit of Monta Rosa, with tourmaline veins, garnets, andalumps, and sillimanite fibers.
Looking at Clough Quartzite, Cragg Mountain trail, Northfield, MA.
Sarah, done with her sandwich. Not sure if it was the finest.
Jeremy on Littleton Schist, with large sillimanite pseudomorphs after andalusite on the rock surface to the right.
Intrusion breccias and other intrusive features in the roots of the Taconic island arc, Shelburn Falls, Massachusetts.
Metamorphosed Cambro-Ordovician volcaniclastic sediments on the east side of the Berkshires. Abundant quartz veins and glacial striations.
Walloomsac metamorphosed calcareous sandstone, Rt. 8, North Adams, MA.
Lunch on Black Precipice. Garnet- and tourmaline-bearing granite dikes and sills visible in the schist.
Sarah and Sarah walking up to Bald Rock.
Part of the class.
Group photo on Crag Mountain, Erving, Massachusetts, view to northeast.
Metamorphosed tonalitic intrusives of the Taconian arc complex, Shelburne Falls, MA.
Snoozing on the flysch and chips outcrop, eastern Berkshires, Massachusetts.
The whole hiking crew.
End of the trip on the summit of Crag Mountain, on Silurian Clough quartzite which is made out of deformed quartz pebbles and cobbles.
Looking at leuconorite, cut by numerous ferrosyenite dikes that form an extremely block-rich intrusion breccia.
Looking closely at the corona textures and the green plagioclase flow foliation in a corona gabbro, near Schroon Lake.
Looking back from the location above to the Billings Fold itself.
Large sillimanite pseudomorph after andalusite, ~35 cm long.