ARE THE MOAT MOUNTIAN VOLCANIC ROCKS OF NEW HAMPSHIRE REALLY OF VOLCANIC ORIGIN? MOAT MAYBE, KEARSARGE NO

Kearsarge Mountain is part of the White Mountain batholith located in north-central New Hampshire. Rocks that make up Kearsarge Mountain are igneous in origin and have been assigned to the Moat Mountain Volcanic Series; interpreted to represent volcanic eruptive and intracaldera tuffs and breccias. Samples were collected from the base to the summit of the mountain (670 m section) for mineralogic and textural analyses. The results of textural analyses show that the rocks exposed on Kearsarge Mountain are coarsely crystalline and contain abundant clasts of country rock. In nearly all cases, clasts are rounded and many appear to have partially melted at the margins. While some samples do show eutaxitic textures and shattered grains consistent with an volcanic origin the majority of the samples show a coarse grained interlocked intrusive texture consisting of quartz + K-feldspar + plagioclase + biotite+/- hornblende. Several samples show granophyric and myrmekitic intergrowths and hornblende grains show dehydration rims (magnetite/ilmenite). These textures support the conclusion that the Keasarge Mountain samples studied solidified in the lid of the caldera yet shallow enough to retain textural evidence for eruptive/ degassing events. The abundance of fragmented and partially melted clasts (country-rock) and the large crystal size of these samples suggest that these parent magmas cooled slowly as a portion of the roof of a large magma chamber at depth and do not represent portions of ignimbrite deposits erupted at the surface. Future work will focus on mineral and whole rock geochemical data. All of the samples are being analyzed for bulk and trace element chemistry using X-ray Fluorescent spectrometry (XRF) and Inductively Coupled Plasma Mass Spectrometry (ICPMS)) and these data along with mineral chemical data (Electron Microprobe) will be used to compare Kearsarge samples with those from nearby Moat Mountain.