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

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