The Storm King granite at Bear Mountain, New York, occupies the core of a syncline in the earlier crystalline complex of the Hudson Highlands. It is part of a larger synclinal pluton whose accordance with the northeast-plunging structure is shown by conformable contacts and mineral alignment in both the granite and the country rocks.

Reasonably constant mineral composition, flow structures of early hornblende crystals, and inclusions confined to the margins of the granite body indicate magmatic intrusion. Absence of secondary foliation and lack of tectonic fabric patterns in the granite suggest post-tectonic emplacement.

The concept of “exchange of space” between the rising magma and the country rocks subsiding into the emptying magmatic chamber is proposed to account for the lack of evidence indicating lifting of the overlying rocks by forcible injection of the granite.

In contrast to most fusion tectonites described, quartz c axes do not have clearly preferred orientations. Anomalous relations between dimensional and lattice orientation of the larger quartz grains are tentatively explained by differential solution of quartz by hydrothermal end-stage products of magmatic (Storm King granite) origin.

Field and statistical studies of principal joint systems reveal concentrations of longitudinal, cross, and diagonal fractures. Joint patterns in the Storm King granite simulate those in the Highlands complex. Several possible mechanisms are discussed to explain their development.

Interpretation of faults in conjunction with other structural data is used to distinguish between the effects of Precambrian and Paleozoic deformation intervals.

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