Silurian plutonism in the Trinity terrane (Neoproterozoic and Ordovician), Klamath Mountains, California, United States

Abstract

New data indicate that the Trinity terrane of northern California is a polygenetic composite terrane rather than a single slice of oceanic lithosphere. We suggest approximately one third of the Trinity terrane consists of Silurian intrusive rocks that represent the roots of a previously unrecognized Silurian magmatic arc. Crosscutting relations and U‐Pb zircon isotopic data document at least one early Paleozoic deformation in the Trinity terrane of northern California. A ductile shear zone between Neoproterozoic metagabbro and Ordovician(?) harzburgite is intruded by the Upper Silurian China Mountain pluton. This evidence indicates a major early Paleozoic shear zone formed in the eastern Klamath Mountains after the Middle Ordovician but prior to Late Silurian plutonism.

Tectonic implications of detrital zircon data from Paleozoic and Triassic strata in western Nevada and Northern California

“…Ages of igneous rocks in eastern Klamath and Black Rock terranes are from Miller and Harwood (1990) and Wallin et al (1995). Numbers in boxes refer to provenance links listed in Table 1. ably within ~1000 km of their present positions along the Cordilleran margin.…”

Detrital zircon geochronologic study of upper Paleozoic strata in the eastern Klamath terrane, northern California

“…If older zircons were recycled from the Yreka terrane, all of the detritus in the Bragdon Formation could have been derived from the eastern Klamath terrane and its underlying basement. (Wallin et al, this volume), and Trinity terrane (Wallin et al, 1988(Wallin et al, , 1995Metcalf et al, 1998). Note that each curve represents all detrital zircon ages from sample or set of samples, and that curves are normalized according to number of constituent grains.…”

“…et al, 1998). The Trinity complex is considered to be part of an ophiolite complex by and Boudier et al (1989), but other workers have interpreted the complex to have formed in an arc-type setting (Quick, 1981;Jacobsen et al, 1984;Saleeby, 1992;Miller and Harwood, 1990;Wallin et al, 1995;Metcalf et al, 1998). The Yreka terrane structurally overlies both the central metamorphic belt and the Trinity complex.…”

“…The interpreted ages shown in Table 1 and plotted in Figure 6 are Miller and Harwood, 1990;Potter et al, 1977Potter et al, , 1990Wallin et al, 1988Wallin et al, , 1995Metcalf et al, 1998). 206 Pb*/ 238 U ages for the <1.0 Ga grains, whereas ages for the older grains are projected from 100 Ma.…”

“…570 Ma (Wallin et al, 1988). Intrusive rocks have age groups of 398-431, 440-475, and 565-570 Ma (Wallin et al, 1988(Wallin et al, , 1995Metcalf 100 G.E. Gehrels and M.M.…”