Cavendish Formation - marble member

Highly variable unit. Includes white, coarse-grained calcite marble; beige to gray, medium- to coarse-grained phlogopite-tremolite-dolomite-quartz-(±talc) marble; greenish actinolite-dolomite-calcite marble; phlogopite-diopside-scapolite-calcite-dolomite marble; and minor quartzite, diopside quartzite, and schistose bluish-gray marble. Contains pods, stringers, and larger masses of granite pegmatite and interlayered aplitic gneiss. Marble and calc-silicate rocks are identical to units (Y2cs) within the biotite-quartz-plagioclase paragneiss member (Y1,2bg) of the Mount Holly Complex of the Green Mountain massif and eastern domes. Mount Holly Complex paragneiss. Rocks of the Green Mountain and Lincoln Mountain massifs and eastern domes. The term “Cavendish Formation” is restricted to two belts of rocks within the Chester dome; the larger belt occurs at Cavendish and on Hawks Mountain, and a less extensive belt, containing similar rocks, occurs near Star Hill. An Early Mesoproterozoic age is here favored for the Cavendish Formation on the basis of (1) the presence of deformed pegmatite (Y3Cp) and areas of Felchville Gneiss (Y1fg and Y1fga) within the Cavendish and (2) the marked resemblance of members of the Cavendish to aluminous and feldspathic schists, calc-silicate rocks, and quartzites within the Mount Holly Complex. Similarities to rocks of the Hoosac Formation are also striking and cannot be altogether dismissed; however, the Hoosac Formation lacks pegmatite and contains distinctive and well-bedded albitic granofels, mafic volcanics, and coarse pebble-to-cobble conglomerate, all absent from the Cavendish. Zircons from a quartzite lens in dolomite marble at locality 4 have Pb-Pb ages between 1,290 and 934 Ma and suggest some of the marble of the Cavendish may be younger than the Felchville Gneiss (Karabinos and others, 1999). Retrograded muscovite-rich, chlorite-spotted, chloritoid-bearing quartz phyllites and garnet granofels and other rocks of the Wilcox Formation (Y2wxs) closely resemble those of the Cavendish Formation, as do chloritic-muscovitic retrograded Y2rs members of the Mount Holly Complex in the Green Mountain massif. Dolomite marble, talc-tremolite rock, diopside quartzite, calc-silicate gneiss, and lustrous chlorite-spotted, chlorite-muscovite-rich retrograded garnet gneiss and schist in the Mount Holly Complex contain abundant pegmatite (Y3Cp) on Blue Ridge Mountain in Chittenden and are identical but lower-grade correlatives of the Cavendish Formation. The coarse garnet-staurolite- and kyanite-bearing Gassetts Schist Member is interpreted to be an Acadian remetamorphosed product of the retrograde aluminous rocks now seen throughout the Mount Holly Complex of the Green Mountain massif and in the Pine Hill area.
State Vermont
Name Cavendish Formation - marble member
Geologic age Early Mesoproterozoic
Lithologic constituents
Major
Metamorphic > Metasedimentary > Metacarbonate > MarbleIncludes white, coarse-grained calcite marble; beige to gray, medium- to coarse-grained phlogopite-tremolite-dolomite-quartz-(±talc) marble; greenish actinolite-dolomite-calcite marble; phlogopite-diopside-scapolite-calcite-dolomite marble; and minor quartzite, diopside quartzite, and schistose bluish-gray marble.
Minor
Metamorphic > Metasedimentary > ParagneissContains pods, stringers, and larger masses of granite pegmatite and interlayered aplitic gneiss.
Igneous > Plutonic > Granitic > Leucocratic-granitic > PegmatiteContains pods, stringers, and larger masses of granite pegmatite and interlayered aplitic gneiss.
Metamorphic > Metasedimentary > Metaclastic > QuartziteMinor quartzite, diopside quartzite.
References
NGMDB product
Counties Windsor