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

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