Overview of Early Paleozoic magmatism in the eastern Klamath Mountains, California
- Univ. of Las Vegas, NV (United States)
- Univ. of Nebraska, Lincoln (United States)
Igneous rocks of the Yreka and Trinity terranes record a complex history of magmatic events that occurred discontinuously over a 200-m.y. period between the Early Cambrian and the Middle Devonian. Lower Cambrian rocks occur as fault-bounded massifs along the northwestern margin of the Trinity terrane, and as tectonic blocks in melange of the Yreka terrane. The textures and structures of the strongly foliated, ductilely deformed Cambrian rocks indicate a complicated tectonic history prior to their juxtaposition with younger rocks of the Trinity and Yreka terranes. Samples dated as Cambrian (570-565 Ma) consist of tonalite and metagabbro; one tonalite contains inherited Precambrian zircon. Ordovician ultramafic and mafic rocks of the Trinity terrane range in age from 472 to 435 Ma. Two plagiogranites dated at 475 and 469 Ma are presumably also related genetically to the oceanic lithosphere represented by the ultramafic rocks. Basaltic to andesitic pillow lavas, flows and dikes occur locally within the Yreka and Trinity terranes. Within melange, these poorly dated occurrences may be Cambrian, Ordovician, or Silurian in age. However, volcanic rocks that overlie the melange are constrained to be Early to Middle Devonian in age and may be a minor northern manifestation of the well developed Devonian magmatic arc in the Redding terrane to the south. These minor Lower to Middle Devonian volcanics and the dikes that presumable fed them are undeformed, indicating that they were erupted after the Yreka and Trinity terranes were amalgamated. Small swarms of sheeted dikes related to this volcanism suggest eruption during post-amalgamation extension.
- OSTI ID:
- 5141091
- Report Number(s):
- CONF-9103128-; CODEN: AABUD
- Journal Information:
- AAPG Bulletin (American Association of Petroleum Geologists); (United States), Vol. 75:2; Conference: American Association of Petroleum Geologists (AAPG)/Society of Economics, Paleontolgists, and Mineralogists (SEPM)/Society of Exploration Geophysicists (SEG)/Society of Professional Well Log Analysts (SPWLA) Pacific Section annual meeting, Bakersfield, CA (United States), 6-8 Mar 1991; ISSN 0149-1423
- Country of Publication:
- United States
- Language:
- English
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