Mafic rocks of the Adirondack Highlands: One suite or many

Conference · Mon Mar 01 04:00:00 EST 1993 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5707833

Whitney, P R ^[1]

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1. Geological Survey, Albany, NY (United States). New York State Museum

Mafic rocks in the granulite facies terrane of the Adirondack Highlands form at least 3 and possibly as many as 6 groups, based on field, petrographic, and geochemical criteria. Most abundant is the olivine metagabbro-amphibolite group (OMA), equivalent to the mafic suite'' of Olson (J. Petrol. 33:471, 1992). OMA occurs in irregular to tabular bodies, locally with intrusive relations, in all major rock types in the E and central Highlands. OMA is strongly olivine normative and forms a continuous differentiation series (Olson, 1992). Plagioclase-two pyroxene-garnet granulites (PGG) form dikes up to several m wide, in anorthositic host rocks. PGG are ferrogabbroic or ferrodioritic and approximately silica saturated. Two subgroups differ sharply in Mg, P, and trace elements. Ferrodiorite and monzodiorite gneisses (FMG), quartz normative and commonly migmatitic, occur in several large bodies in the NE Highlands and as extensive thin sheets in the W and SE Highlands, in association with anorthositic rocks. Three subgroups are distinguishable using Mg/Fe ratios and trace elements. Major element least-squares modeling suggests that both PGG and FMG could be derived by fractionation of gabbroic anorthosite liquids. A differentiation series is not evident, however, and both trace element (Ba, Rb, Sr, Zr and REE) data and normative plagioclase (An [>=] plag. in anorthosite) indicate a more complex origin. One subgroup of FMG may be early cumulates of the mangerite-charnockite suite. The chemistry of OMA, PGG, and FMG reflects their evolved nature and cannot be readily interpreted in terms of magma sources.

• OSTI ID: 5707833
• Report Number(s): CONF-9303211--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 25:2
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ADIRONDACK MOUNTAINS
APPALACHIAN MOUNTAINS
CHEMISTRY
DEVELOPED COUNTRIES
ELEMENTS
GARNETS
GEOCHEMISTRY
GEOLOGIC FORMATIONS
GEOLOGY
GRANULITES
METALS
METAMORPHIC ROCKS
MINERALOGY
MINERALS
MOUNTAINS
NEW YORK
NORTH AMERICA
OLIVINE
OXIDE MINERALS
OXYGEN COMPOUNDS
PARAGENESIS
PETROCHEMISTRY
PETROGENESIS
PETROGRAPHY
PETROLOGY
PYROXENES
QUARTZ
RARE EARTHS
ROCKS
SILICATE MINERALS
SILICATES
SILICON COMPOUNDS
USA