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![Map showing principal elements of the Klamath Mountains province and area sampled
during the present study. Adapted from Mankinen et al. [1996] and Wallin et al. [1995].](profile/Edward-Mankinen/publication/260408134/figure/fig1/AS:297057337266176@1447835396029/Map-showing-principal-elements-of-the-Klamath-Mountains-province-and-area-sampled-during.png)
Map showing principal elements of the Klamath Mountains province and area sampled during the present study. Adapted from Mankinen et al. [1996] and Wallin et al. [1995].
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[1] New paleomagnetic results from the eastern Klamath Mountains of northern California show that Neoproterozoic rocks of the Trinity ophiolitic complex and overlying Middle Devonian volcanic rocks are latitudinally concordant with cratonal North America. Combining paleomagnetic data with regional geologic and faunal evidence suggests that the Trin...
Contexts in source publication
Context 1
... The Klamath Mountains province of northern Cal- ifornia and southern Oregon consists of arcuate structural belts comprising large fragments of oceanic and island arc basement that were juxtaposed during repeated accretion- ary episodes from early Paleozoic to late Mesozoic time ( Figure 1). The oldest rocks are in the Eastern Klamath plate [Irwin, 1981], which consists of Neoproterozoic, Paleozoic, and Mesozoic sedimentary and volcanic depos- its, and an underlying slab of oceanic lithosphere repre- sented by the Trinity mafic -ultramafic sheet [Irwin, 1977]. ...
Context 2
... latter is the largest expanse of ophiolitic rocks in western North America; its sheet-like nature has long been recognized [Irwin and Bath, 1962;Irwin and Lipman, 1962;LaFehr, 1966] because magnetic and gravity studies, combined with regional relationships, indicate that it is a relatively thin subhorizontal sheet overlying a less dense basement. Geophysical evidence [LaFehr, 1966;Griscom, 1973;Fuis and Zucca, 1984;Blakely et al., 1985] further indicates that the Trinity sheet extends westward beneath Neoproterozoic to Middle Devonian rocks of the Yreka - Callahan area Wallin et al., 1991Wallin et al., , 1995 as far as the Central Metamorphic terrane (Figure 1), and eastward for an unknown distance beneath Middle Devonian through Middle Jurassic rocks of the Redding area [Kinkel et al., 1956;Sanborn, 1960;Albers and Robertson, 1961]. Thus, the ophiolitic rocks form oceanic basement beneath the entire eastern Klamath Mountains. ...
Context 3
... Siluro-Devonian pegmatitic gabbro suite intrudes the pre-Late Ordovician blocks of the Trinity Com- plex, as well as the CMFZ suture zone between them, but does not intrude all of the rocks that were historically included [Lipman, 1964] with those of the Trinity subter- rane. The Siluro-Devonian gabbros are completely absent from the thin septum of mafic and ultramafic rocks that extends along the western edge of the Yreka subterrane adjacent to the Central Metamorphic terrane (Figure 1). Thus, this western septum constitutes a separate and distinct block of oceanic lithosphere that probably repre- sents a remnant of the oceanic plate that lay between the Central Metamorphic terrane and the Yreka -Trinity block. ...
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... demagnetization proved to be the only effective means of obtaining characteristic magnetization directions for these rocks, and one specimen from each core was subjected to progressive thermal demagnetization. Thermal demagnet- izations were performed in air using a magnetically shielded Figure 2. Map of area outlined in Figure 1. Shown are selected elements of the Trinity Complex and overlying rocks, and paleomagnetic sampling localities. ...
Context 5
... Neoproterozoic tonalite blocks within the schist of Skookum Gulch, a mélange unit within the Yreka subter- rane, were found to contain zircons with an inherited continental signature and span the period during which the Trinity ophiolite was forming (Table 1, c). Wallin et al. [2000] also determined that detrital Precambrian zircons within the Antelope Mountain Quartz- ite exhibit a continental signature and that sedimentary structures within the unit support a shallow water environ- ment. ...
Similar publications
New zircon U-Pb geochronology from a peridotite suite near Ranau and the Telupid ophiolite in Sabah, eastern Malaysia, contradict previous studies, which assumed that the Sabah mafic-ultramafic rocks are largely ophiolitic and Jurassic–Cretaceous in age. We show that these rocks formed during a magmatic episode in the Miocene (9.2–10.5 Ma), which i...
Citations
... The Klamath Mountain province is a system of fault-bounded, imbricated lithotectonic units of broadly oceanic affinity that regionally dip eastward (Fig. 1). The lithotectonic units generally decrease in age to the west and structurally downward, with ages ranging from Neoproterozoic remnants in the Eastern Klamath Mountains (Wallin et al., 1995;Mankinen et al., 2002;Lindsley-Griffin et al., 2003, 2006Grove et al., 2008) to Upper Jurassic in the Western Klamath Mountains (Diller, 1903;Irwin, 1960Irwin, , 1994. Although recent interpretation of mantle tomography data suggests that amalgamation of the Klamath terranes may have occurred significantly west of the continental margin prior to latest Jurassic to Cretaceous accretion (e.g., Mihalynuk, 2013, 2017;Clennett et al., 2020), whole-rock Sr and Nd and U-Pb detrital zircon results from the Western Klamath terrane demonstrate connection to the North American continent during Jurassic time (e.g., Frost et al., 2006;LaMaskin et al., 2022). ...
The Upper Jurassic Galice Formation, a metasedimentary unit in the Western Klamath Mountains, formed within an intra-arc basin prior to and during the Nevadan orogeny. New detrital zircon U-Pb age analyses (N = 11; n = 2792) yield maximum depositional ages (MDA) ranging from ca. 160 Ma to 151 Ma, which span Oxfordian to Kimmeridgian time and overlap Nevadan contractional deformation that began by ca. 157 Ma. Zircon ages indicate a significant North American continental provenance component that is consistent with tectonic models placing the Western Klamath terrane on the continental margin in Late Jurassic time. Hf isotopic analysis of Mesozoic detrital zircon (n = 603) from Galice samples reveals wide-ranging εHf values for Jurassic and Triassic grains, many of which cannot be explained by a proximal source in the Klamath Mountains, thus indicating a complex provenance. New U-Pb ages and Hf data from Jurassic plutons within the Klamath Mountains match some of the Galice Formation detrital zircon, but these data cannot account for the most non-radiogenic Jurassic detrital grains. In fact, the in situ Cordilleran arc record does not provide a clear match for the wide-ranging isotopic signature of Triassic and Jurassic grains. When compiled, Galice samples indicate sources in the Sierra Nevada pre-batholithic framework and retroarc region, older Klamath terranes, and possibly overlap strata from the Blue Mountains and the Insular superterrane. Detrital zircon age spectra from strata of the Upper Jurassic Great Valley Group and Mariposa Formation contain similar age modes, which suggests shared sediment sources. Inferred Galice provenance within the Klamath Mountains and more distal sources suggest that the Galice basin received siliciclastic turbidites fed by rivers that traversed the Klamath-Sierran arc from headwaters in the retroarc region. Thus, the Galice Formation contains a record of active Jurassic magmatism in the continental arc, with significant detrital input from continental sediment sources within and east of the active arc. These westward-flowing river systems remained active throughout the shift in Cordilleran arc tectonics from a transtensional system to the Nevadan contractional system, which is characterized by sediment sourced in uplifts within and east of the arc and the thrusting of older Galice sediments beneath older Klamath terranes to the east.
... Lindsley-Griffin 1977). Although its precise tectonic setting and emplacement history are poorly constrained, its association with arc-derived volcanosedimentary formations together with geochemical and geochronological data suggest that it is a dismembered fragment of a former arcrelated ocean basin that may have opened between Rodinia and Laurentia; the Trinity ophiolite itself could represent the youngest remnant of this oceanic domain (Brouxel et al. 1988;Coleman 1986;Mankinen et al. 2002;Wallin et al. 1988;Wallin and Metcalf 1998). ...
In the Trinity ophiolite, California, USA, several mafic-ultramafic plutons intruded a peridotitic host 435 to 405 m.y. ago in a tectonic setting interpreted as an arc-related spreading centre. One of these intrusions, in the Bear Creek area, exposes basal ultramafic cumulates with igneous layering comprising an alternation of uncommonly thin (down to a few mm) layers of dunite, peridotite and pyroxenite that might be specific to this tectonic setting. These layers offer an excellent opportunity to characterise the microstructure of uncommon cumulates from the lower crust using EBSD (Electron Backscatter Diffraction). This “high-frequency” layering rests on underlying lherzolites and grades upward to more massive pyroxenites (i.e. clinopyroxenites with minor olivine-rich layers). Our field observations and data from the Bear Creek cumulates together with the preservation of magmatic features suggest the environment was tectonically stable after the emplacement of the cumulates. A detailed microstructural investigation of all minerals from the Bear Creek cumulates allows us to decipher their magmatic and plastic deformation history. In a structural reference frame defined by the compositional layering and the elongation direction of the surrounding host peridotites, olivine in the cumulates presents a [010]-fibre fabric and rarely a [001](010) fabric. Clinopyroxene shows a concentration of [010] axes normal to the layering plane with [100] and [001] defining girdles. Orthopyroxene mostly has a fabric with [100] and/or [010] subnormal to the layering plane and [001] scattered along a girdle in the plane of layering. All minerals show a strong fabric. We interpret the formation of the developed planar microstructures as a result of magmatic processes, with high contribution of crystal settling. To a lesser extent, compaction could have been operating and may be linked to the rare evidence of plastic deformation. Clusters of axes within the girdles of olivine and pyroxene CPOs preferentially appear close to the direction of elongation of the surrounding peridotites (i.e. N115°). EBSD analysis of the shape-preferred orientation of Bear Creek's minerals revealed a preferential alignment of the olivine and cpx long axis with the N°115 direction. This magmatic lineation and the preferred direction in the CPOs girdles are both consistent with the stretching lineation acquired during solid-state deformation by the mantle peridotite of the Trinity ophiolite. We suggest that a weak magma flux early on and/or an ongoing but limited regional stress could be responsible for these clusters. Although a direct coupling between asthenospheric flow and magmatic flow cannot be invoked in this context of melt intrusion in the lithosphere, this result highlights that the stress field applied on the mantle could have been still active and similar during the formation of Bear Creek intrusion.
Our new field and microstructural data, together with previously presented petrological data, fit a scenario for the evolution of the Trinity ophiolite in which a mantle segment was intruded by a single large batch of primitive boninitic-andesitic melt. Our results emphasise the importance of considering the initial magmatic microstructures and the original shape anisotropy when investigating later deformation in ultramafic rocks.
... Compared with older faunas, these exhibit a greater connection to western Laurentia, as opposed to northern Laurentia-Baltica -Siberia. A Middle Devonian palaeopole from the Redding section (Fig. 9) places the combined Eastern Klamath terranes at 318 either north or south latitude (Mankinen et al. 2002); combined with faunal linkages the terrane probably lay near northwestern Laurentia at that time (Lindsley-Griffin et al. 2008, fig. 11). ...
... Lindsley-Griffin considered the term "Trinity Complex" as best describing the entire assemblage. Paleomagnetic studies of the Neoproterozoic and Middle Devonian Trinity Complex, combined with geologic mapping indicate that those rocks and overlying strata formed in a slowly rifting basin marginal to Rodinia and Laurentia (Mankinen et al., 2002). Paleomagnetic data they describe provide permissive evidence that this forming basin was latitudinally concordant with the North American craton at that time. ...
... Other paleomagnetic studies (Irwin and Mankinen, 1998;Mankinen and Irwin, 1990) have indicated large clockwise rotations for Permian and younger elements within the terrane, but none have provided evidence for significant latitudinal displacements. Thus, the Eastern Klamath terrane seems to have been latitudinally concordant with, and remained somehow related to, Laurentia during its large-scale movements since the early Neoproterozoic breakup of Rodinia although the distance between them may have varied considerably (Lindsley-Griffin et al., 2008;Mankinen et al., 2002). ...
... Comparing the EK terrane Triassic results with the Kent and Irving (2010) 230-Ma reference pole shows no latitudinal displacement (northward 3.0°±11.4°). This latter result agrees with those from all older (Mankinen et al., 2002) and younger (Mankinen et al., 1988) formations from the province that were also studied. The discrepant result from the EK Jurassic data may be more apparent than real; note the large gap in the Kent and Irving (2010) APW path between 160 and 140 Ma. ...
... Compared with older faunas, these exhibit a greater connection to western Laurentia, as opposed to northern Laurentia-Baltica -Siberia. A Middle Devonian palaeopole from the Redding section (Fig. 9) places the combined Eastern Klamath terranes at 318 either north or south latitude (Mankinen et al. 2002); combined with faunal linkages the terrane probably lay near northwestern Laurentia at that time (Lindsley-Griffin et al. 2008, fig. 11). ...
Exotic terranes of inferred Arctic affinity form an outer belt within the North American Cordillera extending from Alaska to northern California. The geological history, fossil and detrital zircon data for these terranes show strong correlations and linkages among them, and many features in common with the northern Caledonides, the Timanide orogen and the Urals. They probably occupied an intermediate position between Baltica, Laurentia and Siberia, in proximity to the northern Caledonides in Early Palaeozoic time. Westward dispersion of these terranes is interpreted to result from development of a Scotia-style subduction system between Laurentia-Baltica and Siberia in Mid-Palaeozoic time - the NW Passage - following closure of the Iapetus ocean. Diachronous orogenic activity from Late Silurian in Arctic Canada to Early Devonian in north Yukon and Alaska records passage of some of these terranes. Westward propagation of a narrow subduction zone coupled with a global change in plate motion, linked to closure of the Rheic Ocean are proposed to have led to initiation of subduction along the western margin of Laurentia. This is recorded by the Late Devonian initiation of arc magmatism along western Laurentia, and the Late Devonian-Early Mississippian Antler orogeny in the western US and Ellesmerian orogeny in the Canadian Arctic.
... Compared with older faunas, these exhibit a greater connection to western Laurentia, as opposed to northern Laurentia-Baltica -Siberia. A Middle Devonian palaeopole from the Redding section (Fig. 9) places the combined Eastern Klamath terranes at 318 either north or south latitude (Mankinen et al. 2002); combined with faunal linkages the terrane probably lay near northwestern Laurentia at that time (Lindsley-Griffin et al. 2008, fig. 11). ...
Palaeozoic to early Mesozoic terranes of the North American Cordillera mostly originated from three distinct regions in Palaeozoic time: the western peri-Laurentian margin, western (Asian) Panthalassa, and the northern Caledonides-Siberia. A review of geological history, fossil and provenance data for the Caledonian-Siberian terranes suggests that they probably occupied an intermediate position between northern Baltica, northeastern Laurentia and Siberia, in proximity to the northern Caledonides, in early Palaeozoic time. Dispersion of these terranes and their westward incursion into eastern Panthalassa are interpreted to result from development of a Caribbean- or Scotia-style subduction system between northern Laurentia and Siberia in mid-Palaeozoic time, termed here the Northwest Passage. Westward propagation of a narrow subduction zone coupled with a global change in plate motion, related to the collision of Gondwana with Laurentia-Baltica, are proposed to have led to initiation of subduction along the western passive margin of Laurentia and development of the peri-Laurentian terranes as a set of rifted continental fragments, superimposed arcs and marginal ocean basin(s) in mid- to late Palaeozoic time. Diachronous orogenic activity from Late Silurian in Arctic Canada, to Early Devonian in north Yukon and adjacent Alaska, Middle Devonian in southeastern British Columbia, and Late Devonian-Early Mississippian in the western USA records progressive development of the Northwest Passage and southward propagation of subduction along western Laurentia.
... Following juxtaposition of the Trinity peridotite and the Ediacaran(?) harzburgite, both were intruded by voluminous Silurian-Devonian (410-435 Ma; Fig. 3) gabbro and pyroxenite and blanketed by coeval volcanic rocks (Schwindinger and Anderson, 1987;Cannat and Lécuyer, 1991;Lindsley-Griffi n, 1991;Petersen et al., 1991;Wallin et al., 1991Wallin and Metcalf, 1998). Eruption of Middle Devonian lavas and feeder dikes occurred after the Yreka and Trinity terranes had been juxta posed Mankinen et al., 2002). ...
... The Yreka and Trinity subterranes are tied together by overlapping Middle Devonian volcanics Mankinen et al., 2002;Lindsley-Griffi n et al., 2006, 2008. Prior to this time, the relationship between the two subterranes is un certain. ...
... Paleomagnetic data exist for Devonian rocks of the Alexander and eastern Klamath terranes. The Middle Devonian vol canic rocks that cap both the Yreka and Trinity subterranes yield a paleolatitude of 31° ± 5°N or S (Mankinen et al., 2002). This differs signifi cantly from paleolatitude reported by Butler et al. (1997) for the Early Devonian Karheen Formation of the Alexander terrane (14° ± 4°N or S). ...
... Following juxtaposition of the Trinity peridotite and the Ediacaran(?) harzburgite, both were intruded by voluminous Silurian-Devonian (410-435 Ma; Fig. 3) gabbro and pyroxenite and blanketed by coeval volcanic rocks (Schwindinger and Anderson, 1987;Cannat and Lécuyer, 1991;Lindsley-Griffi n, 1991;Petersen et al., 1991;Wallin et al., 1991Wallin and Metcalf, 1998). Eruption of Middle Devonian lavas and feeder dikes occurred after the Yreka and Trinity terranes had been juxta posed Mankinen et al., 2002). ...
... The Yreka and Trinity subterranes are tied together by overlapping Middle Devonian volcanics Mankinen et al., 2002;Lindsley-Griffi n et al., 2006, 2008. Prior to this time, the relationship between the two subterranes is un certain. ...
... Paleomagnetic data exist for Devonian rocks of the Alexander and eastern Klamath terranes. The Middle Devonian vol canic rocks that cap both the Yreka and Trinity subterranes yield a paleolatitude of 31° ± 5°N or S (Mankinen et al., 2002). This differs signifi cantly from paleolatitude reported by Butler et al. (1997) for the Early Devonian Karheen Formation of the Alexander terrane (14° ± 4°N or S). ...
The tectonic significance of early Paleozoic convergent-margin rocks of the Alexander and Sierran-Klamath terranes is poorly understood. New phengite 40Ar/39Ar and Rb-Sr results from the schist of Skookum Gulch of the Yreka subterrane in the Klamath Mountains (454 ± 10 Ma) confirm that blueschists are the oldest known subduction-zone rocks of the western North American Cordillera. The blueschists are juxtaposed with kilometer-scale tectonic blocks of ca. 565 Ma tonalite. Detrital zircons from the blueschists require close proximity to a diverse source of cratonal or derivative supracrustal rocks and preclude formation within an isolated intra-oceanic setting. This strong cratonal provenance (mostly 1.0-2.0 Ga, with resolved concentrations of 1.49-1.61 Ga zircon) is also exhibited by adjacent Early Devonian lower greenschist units of the Yreka subterrane (Duzel phyllite and Moffett Creek Formation). Additional results from temporally equivalent arc-derived sedimentary units (Sissel Gulch graywacke and Gazelle Formation) yield strongly unimodal zircon age distributions of early Paleozoic zircon. The results indicate that the Yreka sub-terrane formed at an Ordovician-Silurian- Early Devonian convergent margin near a Mesoproterozoic-Paleoproterozoic craton and Ediacaran crust. Appreciable 1.491.61 Ga zircon within the Yreka subterrane is compatible with a recent biogeographic analysis that indicates a non-Laurentian origin for the eastern Klamath terrane. Additional new data reveal that key early Paleozoic convergent-margin rocks within the northern Sierran-Klamath and Alexander terranes share similar arc and cratonal provenance, including 1.49-1.61 Ga zircon. We hypothesize that the rocks from all three areas are dispersed tectonic fragments that were derived from the same convergent margin and were independently transported to western North America. Of the oro-genic source regions indicated by previous paleomagnetic and biogeographic analysis, the detrital zircon provenance favors western Baltica over eastern Australia.
... If the tectonic accretion history of the adjacent northern California Coast Ranges is considered, the exposed accretionary history spans into the middle Cenozoic, and active tectonic accretion is ongoing along the Pacific margin in the form of the Cascadia subduction zone. The ages of the lithotectonic units range from Neoproterozoic remnants in the eastern Klamath Mountains (Mankinen et al., 2002;Lindsley-Griffin et al., 2003, this volume) to Upper Jurassic in the western Klamath Mountains (Diller, 1903;Irwin, 1960Irwin, , 1994. The age of the lithotectonic units generally decreases to the west as well as structurally downward. ...
... Another ophiolitic assemblage that has a long history of study by various workers is the Trinity ultramafic-mafic complex (Trinity subterrane of Irwin, 1994) exposed in the eastern Klamath Mountains (Lipman, 1964;Lindsley-Griffin, 1977, 1983Lindsley-Griffin and Griffin, 1991;Quick, 1981;Boudier et al., 1989;Wallin and Metcalf, 1998;Metcalf et al., 2000;Mankinen et al., 2002). This suite of ultramafic and mafic rocks is the oldest ophiolitic assemblage in the Klamath Mountains province but is also a polygenetic suite of rocks that has yielded a broad range of ages-from Neoproterozoic through Early Devonian (Mattinson and Hopson, 1972;Jacobsen et al., 1984;Wallin and Metcalf, 1998;Metcalf et al., 2000;Mankinen et al., 2002;Lindsley-Griffin et al., 2003). ...
... Another ophiolitic assemblage that has a long history of study by various workers is the Trinity ultramafic-mafic complex (Trinity subterrane of Irwin, 1994) exposed in the eastern Klamath Mountains (Lipman, 1964;Lindsley-Griffin, 1977, 1983Lindsley-Griffin and Griffin, 1991;Quick, 1981;Boudier et al., 1989;Wallin and Metcalf, 1998;Metcalf et al., 2000;Mankinen et al., 2002). This suite of ultramafic and mafic rocks is the oldest ophiolitic assemblage in the Klamath Mountains province but is also a polygenetic suite of rocks that has yielded a broad range of ages-from Neoproterozoic through Early Devonian (Mattinson and Hopson, 1972;Jacobsen et al., 1984;Wallin and Metcalf, 1998;Metcalf et al., 2000;Mankinen et al., 2002;Lindsley-Griffin et al., 2003). Multiple hypotheses have been advanced for this assemblage; the most recent interpretation is that it is a supra-subduction ophiolite formed during forearc rifting in an incipient intra-oceanic arc (Wallin and Metcalf, 1998;Metcalf et al., 2000). ...
The Klamath Mountains province of northwestern California and southwestern Oregon is a classic example of a mountain belt that developed by the tectonic accretion of rock assemblages of oceanic affinity during progressive crustal growth along an active continental margin. Consequently, the Klamath Mountains province has served as an important model for the definition and application of the terrane conceptas applied to the evolution of Phanerozoic orogenic belts. Early regional studies divided the Klamath Mountains province into four arcuate lithic belts of contrasting age (from east to west): the eastern Klamath, central metamorphic, western Paleozoic and Triassic, and western Jurassic belts. The lithic belts are bounded by regional thrust faults that commonly include ophiolitic assemblages in the hanging-wall block. The age of thrusting is a complex problem because of structural overprinting, but generallythe age of regional thrust faulting is older in eastern parts of the province and younger to the west. The lithic belts were subsequently subdivided into many tectonostratigraphic terranes, and these lithotectonic units are always fault-bounded. Few of the regional faults are fossil subduction zones, but multiple episodes of high pressure- low temperature (blueschist-facies) metamorphism are recognized in the Klamath Mountains province. The tectonostratigraphic terranes of the Klamath Mountains province are intruded by many composite, mafic to felsic, arc-related plutons, some of which reach batholithic dimensions. Many of these plutonic bodies were emplaced during the Jurassic; however, radiometric dates ranging from Neoproterozoic through Early Cretaceous have been determined from (meta)plutonic rocks of the KlamathMountains province. The orogenic evolution of the province apparently involved the alternation of contraction and extension, as exemplified by the Jurassic history of the province. Widespread Middle Jurassic plutonism and metamorphism is associated with a poorly understood contractional history followed by the development of the Preston Peak-Josephine ophiolite and Upper Jurassic Galice Formation in a probable transtensional inter-arc basin. During the Late Jurassic Nevadan orogeny, this basin collapsed, and rocks of the Galice Formation were thrust beneath the Rattlesnake Creek terrane along the Orleans fault. During this regional deformation, the Galice Formation experienced polyphase deformation and was metamorphosed under lower greenschist-facies conditions. Immediately following thrusting, the hangingwall and footwall blocks of the Orleans fault were intruded by a suite of composite, mafic to felsic plutons (i.e., western Klamath plutonic suite) that have oceanic-arc geochemical and isotopic characteristics, indicating a subduction-zone petrogenesis for the magmas. The western boundary of the Klamath Mountains province is a regional thrust fault that emplaced the rocks of the province above Early Cretaceous blueschist-facies rocks (South Fork Mountain Schist) of the Franciscan Complex. Neogene structural doming is manifested in the north-central Klamath Mountains by the Condrey Mountain window, which exposes the high pressure-low temperature Condrey Mountain Schist framed by chiefly amphibolite-facies metamorphic rocks of the Rattlesnake Creek terrane.
... Events that preceded the Central Metamorphic episode prior to Silurian-Devonian time are not clearly understood and are not shown in the succession of diagrams on Sheet 2. The oldest rocks of the Klamath Mountains are Neoproterozic and they predate the Central Metamorphic episode by possibly a hundred million years or more. They include ophiolitic rocks of the Trinity subterrane and the Antelope Mountain Quartzite of the Yreka subterrane (see Mankinen and others, 2002). In the Sierra Nevada, correlatives of the ancient ophiolitic rocks may be part of the Feather River terrane. ...
