1. ULTRAMAFIC ROCKS
EARTH’S MANTLE IS COMPOSED OF ULTRAMAFIC ROCKS
ULTRAMAFICS (ULTRABASIC) ROCKS ARE IGNEOUS & META-IGNEOUS
VERY LOW SILICA, LESS THAN 45%
GENERALLY >18% MgO, HIGH FeO, LOW POTASSIUM
>90% MAFIC MINERALS(DARK COLORED MINERALS, HIGH MAGNESIUM & IRON CONTENT)

2. INTRUSIVE ULTRAMAFIC ROCKS
IUGS Classification diagram for intrusive ultramafic rocks based on modal percentages of mafic minerals. Green area represents typical mantle peridotite

3. PERIDOTITE HARZBURGITE LHERZOLITE
OSMIUM PYROPE GARNET GARNET-BEARING
HARZBURGITE

4. PERIDOTITE – DENSE COARSE-GRAINED ULTRAMAFIC(IGNEOUS)ROCK CONSISTING OF OLIVINE & PYROXENE, CONTAINS LESS THAN 45% SILICA; HIGH IN MAGNESIUM-RICH OLIVINE-- OVER 30% WITH APPRECIABLE IRON
COMPOSITION OF PERIDOTITES VARY RELATIVE TO PROPORTIONS OF PYROXENES, CHROMITE, PLAGIOCLASE, & AMPHIBOLE
PERIDOTITE NODULES FOUND IN CERTAIN BASALTS & DIAMOND PIPES(KIMBERLITE) ARE OF SPECIAL INTEREST TO PALEOGEOLOGISTS: 1) CLUE TO COMPOSITION OF EARTH’S EARLY MANTLE & COMPLEX PROCESS INVOLVED

5. 2) P-NODULES PRESERVE ISOTOPE RATIOS OF OSMIUM (Os) [BLUE-GRAY OR BLUE-BLACK HARD BRITTLE VERY HEAVY POLYVALENT METALLIC ELEMENT WITH HIGH MELTING POINT, TRANSITIONAL METAL IN THE PLATINUM FAMILY] & OTHER ELEMENTS THAT RECORD THE PROCESSES OVER 3B YEARS BP. TYPES OF PERIDOTITE: 1) DUNITE – MORE THAN 90% OLIVINE WITH Mg/Fe RATIO OF ABOUT 9:1 2)WEHRLITE – MOSTLY COMPOSED OF OLIVINE PLUS CLINOPYROXENE 3) HARZBURGITE – MOSTLY COMPOSED OF OLIVINE PLUS ORTHOPYROXENE & LOW PROPORTIONS OF

6. INTRUSIVE ULTRAMAFICS – FOUND IN LARGE LAYERED INTRUSIONS WHERE DIFFERENTIATED ROCK TYPES OFTEN OCCUR IN LAYERS
ULTRAMAFIC INTRUSIVE INCLUDES DUNITES, PERIDOTITES, PYROXENITES & TROCTOLITE (RARE VARIETY HAS GREATER PERCENTAGE OF CALCIC PLAGIOCLASE); THESE GRADE INTO ANORTHOSITES
GABBRO & NORITE OFTEN OCCUR IN UPPER PORTION OF LAYERED ULTRAMAFIC SEQUENCES; HORNBLENDITE & RARELY PHLOGOPHITE ARE ALSO FOUND

7. VOLCANIC ULTRAMAFIC ROCKS
RARE OUTSIDE OF ARCHEAN
ESSENTIALLY RESTRICTED TO NEOPROTEROZOIC OR EARLIER
BONINITE LAVAS WITHIN BACK-ARC BASINS ( MANUS TROUGH, NEW GUINEA)
SUBVOLCANIC ULTRAMAFIC ROCKS & DYKES ARE RARE
EXAMPLES OF VOLCANIC ULTRAMAFIC ROCKS:
KOMATITE – HOST TO ORE DEPOSIT OF NICKEL
PICRITIC BASALT

8. ULTRAPOTASSIC ULTRAMAFIC ROCKS
ULTRAPOTASSIC ULTRAMAFIC & MELILITIC ROCKS – TECHNICALLY CONSIDERED SEPARATE GROUP BASED ON MELTING CRITERIA
HIGHLY SILICA-UNDER-SATURATED ROCKS WITH >18% MgO
ULTRAPOTASSIC, ULTRAMAFIC IGNEOUS ROCKS SUCH AS LAMPROPHYRE, LAMPROITE & KIMBERLITE OCCUR AS DIKES, DIATREMES, LOPOLITHS OR LACCOLITHS ARE RARELY INTRUSIONS
KIMBERLITE & LAMPROITE OCCUR AS VOLCANIC

9. DIATREMES & MAARS OCCUR AS SUBVOLCANIC
VENTS OF PROTEROZOIC LAMPROITE (ARGYLE DIAMOND MINE), CENOZOIC LAMPROITE(GAUSSBERG ANTARCTICA), DEVONIAN LAMPROITE( SCOTLAND)
KIMBERLITE IN CANADA, SOUTH AFRICA & RUSSIA
CARBONATITE ARE RARE HIGH-CARBONATE, LOW-SILICA IGNEOUS ROCK

10. METAMORPHIC ULTRAMAFIC ROCKS
METAMORPHISM OF ULTRAMAFIC ROCKS IN THE PRESENCE OF WATER AND/OR CARBON DIOXIDE RESULTS MAIN CLASSES: 1) TALC CARBONATE 2) SERPENTINITE
SERPENTINIZATION REACTIONS RESULT TO CHLORITE-SERPENTINE-AMPHIBOLE TYPES ASSEMBLAGES WHEN METAMORPHIC FLUIDS IN CONTACT WITH ULTRAMAFIC ROCKS HAVE LESS THAN 10% CO2
TALC CARBONATION REACTIONS RESULTS TO GRENNSCHIST THRU GRANULITE WHEN METAMORPHIC FLUIDS HAS LESS THAN 10% CO2

11. DISTRIBUTION IN SPACE & TIME
MAJORITY OF ULTRAMAFICS ARE EXPOSED IN OROGENIC BELTS & PREDOMINATE IN ARCHEAN & PROTEROZOIC; ULTRAMAFIC MAGMAS IN PHANEROZOIC ARE RARE & FEW RECOGNIZED
TRUE ULTRAMAFIC LAVAS
MANY SURFACE EXPOSURES OF ULTRAMAFICS OCCUR IN OPHIOLITE COMPLEXES WHERE DEEP MANTLE-DERIVED ROCKS HAVE BEEN OBDUCTED UNTO CONTINENTAL CRUST & {ISLAND ARCS] ALONG & ABOVE SUBDUCTION ZONES

12. PLATE TECTONICS

14. ULTRAMAFIC ROCKS & REGOLITH
ALKALI-RICH ULTRAMAFIC ROCKS PROVIDE EXCELLENT BALANCE NUTRIENTS TO THE SOILS; PERIDOTITE & SERPENTINITE HAVE HIGH RATIO OF MAGNESIUM TO CALCIUM BUT DEFICIENT IN POTASSIUM & PHOSPORUS; CONTAIN TOXIC AMOUNTS OF CHROMIUM & NICKEL
ULTRAMAFIC ROCKS CREATE UNIQUE VEGETATION: ULTRAMAFIC FOREST/VEGETATION IS TYPICALLY STUNTED OR BARREN & HOME TO ENDEMIC SPECIES ADAPTED TO METALLIC SOILS
WEATHERED ULTRAMAFIC ROCKS FORM LATERITIC NICKEL ORE DEPOSITS