Middle Eocene dike swarms and their relation to contemporaneous plutonism, volcanism, core-complex mylonitization, and graben subsidence, Okanogan Highlands, Washington

Journal Article · Thu Nov 01 04:00:00 EST 1990 · Geology; (USA)

DOI:https://doi.org/10.1130/0091-7613(1990)018<1082:MEDSAT>2.3.CO;2· OSTI ID:5680070

McCarley Holder, G A ^[1]; Holder, R W ^[2]; Carlson, D H ^[3]

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1. Washington State Univ., Pullman (USA)
2. Georgia Southern College, Statesboro (USA)
3. California State Univ., Sacramento (USA)

Sheeted porphyry dike swarms are concentrated along and parallel to the margins of the Republic and Keller grabens in northeast Washington. They were emplaced during graben subsidence and, in part, during mylonitization of the Kettle and Okanogan domes (core complexes) above the transition into the brittle deformation zone during Eocene regional extension. The swarms consist of older high-K biotite rhyolite and younger high-K hornblende dacite and andesite dikes. The biotite rhyolite is correlative with the basal O'Brien Creek Formation now exposed in the grabens but has no documented plutonic equivalent in the adjacent Colville batholith. The hornblende dacite and andesite dikes (Scatter Creek Formation) are divided into (1) a low-Zr, low-K{sub 2}O type that fed the lower part of the Sanpoil Volcanics and (2) a high-Zr, hig-K{sub 2}O type that fed the upper part of the Sanpoil Volcanics, respectively. The Scatter Creek Formation dikes are the hypabyssal equivalents of both the Devils Elbow intrusive suite and the earlier phases of the Herron Creek intrusive suite in the Colville batholith. The occurrencd of the dike swarms both within and adjacent to grabens filled with comagmatic volcanic rocks demonstrates that the graben fill was deposited in situ during regional extension and is not an allochthonous fault block transported to its present location during regional compression.

• OSTI ID: 5680070
• Journal Information: Geology; (USA), Journal Name: Geology; (USA) Vol. 18:11; ISSN GLGYB; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALKALI METAL COMPOUNDS
BIOTITE
CHALCOGENIDES
CHEMISTRY
DEFORMATION
DEPOSITION
DIKES
ELEMENTS
FEDERAL REGION X
GEOCHEMISTRY
GEOLOGIC FORMATIONS
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
GEOLOGY
IGNEOUS ROCKS
METALS
MICA
MINERALS
NORTH AMERICA
OXIDES
OXYGEN COMPOUNDS
PLUTONIC ROCKS
POTASSIUM COMPOUNDS
POTASSIUM OXIDES
ROCKS
SILICATE MINERALS
TRANSITION ELEMENTS
USA
VOLCANIC REGIONS
VOLCANIC ROCKS
VOLCANISM
WASHINGTON
ZIRCONIUM