Age Determinations of Pegmatites in Topsham, Maine

“…Mining ended sometime before 1950 (Cameron and others, 1954; King, 2000). Five pegmatites at the Red Hill quarries in the eastern part of the quadrangle were explored for beryl in the late 1940s (Shainin, 1949).The pegmatite at Rumford Whitecap was explored for beryl and feldspar based on the success of the deposits at Plumbago and Black Mountains. In 1961, the Whitecap Mountain Syndicate drilled two exploration holes at the summit with a combined length of 994 feet under the direction of Moyd (1961).…”

mentioning

confidence: 99%

Geology of the Lower Ellis River Valley and Rumford Whitecap Mountain, Andover and Rumford, Maine

Spigel¹,

Whittaker²,

Gordon³

2017

New England Intercollegiate Geological Conference 2017

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INTRODUCTION PurposeThe East Andover quadrangle was selected for surficial mapping during the 2016 field season as part of the Maine Geological Survey's STATEMAP program. The area was coarsely cataloged by Stone (1899) and Leavitt and Perkins (1935), but the surficial geology had not been officially mapped at a scale finer than the state level of 1:500,000 (Thompson and Borns, 1985), and thus became a priority for the Survey. Bedrock geology of the area was mapped at the 1:62,500 scale (Rumford quadrangle) by Moench and Hildreth (1976). The recent surficial mapping efforts (Locke and others, 2017; Weddle and others, 2017) provided a reminder of how much the area has to offer the visiting geologist, with everything from pegmatites and a rich mining history to eskers and stream terraces. This field trip will provide participants with the opportunity to view a subsample of the geologic features in the East Andover quadrangle and to consider their formative processes. Figure 1 offers an overview of the trip route with stop locations. We will begin in the southeast part of the quadrangle, work our way up the Ellis River Valley, then loop back down to the central portion of the quadrangle to end the day at Rumford Whitecap Mountain. Physiography OverviewOn a broad scale, the East Andover quadrangle lies within the Central Highlands of New England, which contains a wide range of topography and the highest peaks in the region (Denny, 1982). Hanson and Caldwell (1989) focused in on Maine and refined Denny's classification, but this did not significantly change the description of the East Andover area, which was placed in the Central Maine Highlands. This geomorphic region is comprised of several mountain ranges, including the Mahoosuc Range and Blue Mountains, which lie to the west/southwest and north/northeast of the quadrangle, respectively. The foothills of these ranges and lesser peaks make up the topography within the quadrangle and to the south/southeast. Many locals simply refer to this region as the Western Maine Mountains. Tributaries that eventually form the West Branch of the Ellis River flow from the Dunn Notch and Sawyer Notch areas to the west and northwest of the quadrangle. Tributaries of the East Branch of the Ellis River make their way from the Black Brook Notch, Little Ellis Pond, and Ellis (a.k.a Roxbury) Pond areas to join the West Branch just south of Andover village. The area to the north and northeast of this confluence is a relatively large and flat basin formed in the Mooselookmeguntic Pluton. Hanson and Caldwell (1989) attributed broad lowlands that occur within the Central Maine Highlands to underlying plutonic rocks, which are (in most cases) less resistant to weathering and glacial erosion than surrounding metamorphic rocks. The Ellis River flows south from the basin, entering a deep valley that is bounded by Plumbago Mountain and Mount Dimmock to the west and Rumford Whitecap Mountain to the east, eventually reaching the Androscoggin River at Rumford Point. BEDROCK GEOLOGYThe bedrock in th...

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Hydrothermal synthesis and crystal structure of Na(Na,Mn)7Mn22(PO4)180.5H2O, a new compound of fillowite structure type

Keller

Hatert

Lissner

et al. 2006

ejm

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The chemical compound Na(Na,Mn) 7 Mn 22 (PO 4 ) 18 • 0.5H 2 O was synthesized with a Tuttle pressure vessel at 800 °C and 1 kbar during experimental investigations on the conditions of fillowite formation. The crystal structure of a single-crystal, space group R3 (No. 148), a = 15.2741(9), c = 43.334(3) Å, Z = 6, was determined from X-ray intensity data and refined up to R 1 = 0.0728 and R 1{FO>4 c (FO)} = 0.0546. The crystal structure of Na(Na,Mn) 7 Mn 22 (PO 4 ) 18 •0.5H 2 O is similar to the structure of fillowite, Na 6 Ca 3 (Mn,Fe) 21 (PO 4 ) 18. , but a significant difference between the synthetic H 2 O containing compound and fillowite is the replacement of (Na12)O 8 -by Mn(H 2 O) 2 O 5 -polyhedra, which form characteristic six-member rings. The coordination polyhedra around Na12 and Mn12 are so different that simple isomorphous substitution of Na12 by Mn12 is very unlikely, but whole six-member rings either of (Na12)O 8 -or (Mn12)(H 2 O) 2 O 5 polyhedra seem to be distributed statistically over the crystal structure. No indication for ordering, e.g. sheet by sheet, has been observed. Na(Na,Mn) 7 Mn 22 (PO 4 ) 18 • 0.5H 2 O is the first fillowite-like compound for which water is located in the structure from single-crystal study. This result is proved by infrared spectral data and indicates that water can play an essential role in the fillowite structure-type. Structural features of the synthetic compounds Na(Na,Mn) 7 Mn 22 (PO 4 ) 18 •0.5H 2 O, Na 4 Ca 4 Mg 21 (PO 4 ) 18 and fillowite are compared.

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Age Determinations of Pegmatites in Topsham, Maine

Cited by 10 publications

References 0 publications

Guidebook for Field Trips in Western Maine and Northern New Hampshire

Guidebook for Field Trips in Western Maine and Northern New Hampshire

Geology of the Lower Ellis River Valley and Rumford Whitecap Mountain, Andover and Rumford, Maine

Hydrothermal synthesis and crystal structure of Na(Na,Mn)7Mn22(PO4)180.5H2O, a new compound of fillowite structure type

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