Preliminary fission track ages for samples from western Maine: Implications for the low temperature thermal history of the region

Conference · Wed Jan 01 04:00:00 EST 1992 · Geological Society of America, Abstracts with Programs; (United States)

OSTI ID:5589337

Lux, D R ^[1]; Johnson, K ^[2]

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1. Univ. of Maine, Orono, ME (United States). Dept. of Geological Sciences
2. University College, London (United Kingdom)

In order to elucidate the low temperature cooling history of the region, 12 preliminary samples from a N-S traverse from the central Sebago batholith to the Chain of Ponds pluton were selected for fission track dating. The range of Ar-40/Ar-39 ages from the selected samples is 140 Ma (371--231 Ma) for biotites, 63 Ma (304--241 Ma) for muscovites and 61 Ma (375--304 Ma) for hornblendes. Twelve samples were dated by the external detector method and yield ages between 114 and 79 Ma. The southern most samples from the Sebago batholith and Songo pluton, within the highest metamorphic zones, are the youngest and range from 101 to 79 Ma. Those from the Mooselookmeguntic and Chain of Ponds plutons, within lower metamorphic zones, vary between 114 and 92 Ma. This general discordance trend is similar but of much smaller magnitude than the regional pattern of Ar-40/Ar-39 cooling ages. The much smaller range of apatite ages than biotite ages suggests that large differences in the thermal regime across of the region during Late Paleozoic time had largely been erased by the Early Cretaceous. The new fission track ages are interpreted to represent regional cooling through the apatite closure temperature, assumed to be ca 100 C. Young apatite ages may be the result of a regional thermal disturbance related to the intrusion of magmas of the White Mountains Plutonic Suite, as the youngest plutons are similar in age to the apatites. Alternatively, they could be the result of regional exhumation of the Acadian orogen. The authors conclude that the latter interpretation is more consistent with their data and attribute the ages to time of regional exhumation and uplift through the apatite closure temperature.

• OSTI ID: 5589337
• Report Number(s): CONF-921058--
• Conference Information: Journal Name: Geological Society of America, Abstracts with Programs; (United States) Journal Volume: 24:7
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
APATITES
BIOTITE
DEVELOPED COUNTRIES
FISSION TRACKS
GEOLOGIC FORMATIONS
GEOTHERMOMETRY
IGNEOUS ROCKS
ISOTOPE DATING
MAINE
MICA
MINERALS
NORTH AMERICA
PARTICLE TRACKS
PHOSPHATE MINERALS
PLUTONIC ROCKS
RESERVOIR TEMPERATURE
ROCKS
SILICATE MINERALS
USA
ZIRCON