Klamath-Blue Mountain lineament, Oregon

Riddihough, R. P.; Finn, Carol A.; Couch, Richard W.

doi:10.1130/0091-7613(1986)14<528:kmlo>2.0.co;2

Cited by 48 publications

(25 citation statements)

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“…The most dominant of these northeast trending anomalies is spatially related to pre-Cenozoic outcrops of the Blue Mountains (Plate 1). Riddihough et al [1986] noted that this anomaly is on strike with an anomaly in the Klamath Mountains and proposed that the two terranes connect beneath the Cascade province in Oregon.…”

Section: Introductionmentioning

confidence: 92%

“…Subtracting the gravitational effects of this prism from the Bouguer anomaly and then applying the same low-pass filter (cutoff 89.25 km) eliminated much of the regional anomaly correlative with regional heat flow. In particular, the northward directed nose of the Bouguer anomaly was replaced with a broad, northeast trending gradient on strike with the Blue Mountains-Klamath Mountains lineament described by Riddihough et al [ 1986]. Blackwell et al [1990a] concluded from this result that a lowdensity zone at 6 km depth is responsible for the regional aspects of the Bouguer anomaly, is also the source of regional heat flow patterns, and disguises gravity anomalies caused by underlying pre-Cenozoic structure.…”

Section: Blackwell Et Almentioning

confidence: 99%

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Extent of partial melting beneath the Cascade Range, Oregon: Constraints from gravity anomalies and ideal‐body theory

Blakely¹

1994

J. Geophys. Res.

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The spatial correlation between a horizontal gradient in heat flow and a horizontal gradient in residual gravity in the Western Cascades of central Oregon has been interpreted by others as evidence of the western edge of a pervasive zone of high temperatures and partial melting at midcrustal depths (5–15 km). Both gradients are steep and relatively linear over north‐south distances in excess of 150 km. The Western Cascades gravity gradient is the western margin of a broad gravity depression over most of the Oregon Cascade Range, implying that the midcrustal zone of anomalous temperatures lies throughout this region. Ideal‐body theory applied to the gravity gradient, however, shows that the source of the Western Cascades gravity gradient cannot be deeper than about 2.5 km and is considerably shallower in some locations. These calculations are unique determinations, assuming that density contrasts associated with partial melting and elevated temperatures in the crust do not exceed 500 kg m−3. Consequently, the gravity gradient and the heat flow gradient in the Western Cascades cannot be caused directly by the same source if the heat flow gradient originates at midcrustal depths. This conclusion in itself does not disprove the existence of a widespread midcrustal zone of anomalously high temperatures and partial melting in this area, but it does eliminate a major argument in support of its existence. The gravity gradient is most likely caused by lithologic variations in the shallow crust, perhaps reflecting a relict boundary between the Cascade extensional trough to the west and Tertiary oceanic crust to the west. The boundary must have formed prior to Oligocene time, the age of the oldest rocks that now conceal it.

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Section: Introductionmentioning

confidence: 92%

Section: Blackwell Et Almentioning

confidence: 99%

Extent of partial melting beneath the Cascade Range, Oregon: Constraints from gravity anomalies and ideal‐body theory

Blakely¹

1994

J. Geophys. Res.

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“…The pre-Tertiary Klamath mountains are composed of multiple accretionary episodes [Irwin, 2003]. Gravity data that cover northern Geochemistry, Geophysics, Geosystems California and southern Oregon between 39 N and 43 N [e.g., Riddihough et al, 1986] do not reveal a large anomaly near the Klamath Mountains, indicating that the accreted terrane is either less dense, less thick or has a deep root. Hence, the Klamath Mountains, in contrast to the denser and stronger Siletzia terrane, are interpreted to be lighter and weaker [Brudzinski and Allen, 2007].…”

Section: Distribution Of Terranesmentioning

confidence: 99%

Central Cascadia subduction zone creep

Schmalzle

McCaffrey

Creager

2014

Geochem. Geophys. Geosyst.

147

329

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“…The structural suture zone of Armstrong et al (1977) separates an area of older basement to the east and north from the accreted terranes to the south and west. The Klamath -Blue Mountains lineament, which trends parallel to (and slightly northwest oij the axial trace of the Blue Mountains antiformal uplift, is a linear region about 50 km wide, containing a Bouguer gravity gradient of 40-60 mGal (1 mGal = 10-3 cm/s2) down to the southeast (Riddihough et al 1986). The regional tectonic context of the CRBG eruptions was probably a back-arc basin (Carlson 1984;Church 1985).…”

Section: Regional Considerationsmentioning

confidence: 98%

Ferro-andesites in the Grande Ronde Basalt: their composition and significance in studies of the origin of the Columbia River Basalt Group

Lambert¹,

Chamberlain²,

Holland³

1995

Can. J. Earth Sci.

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Flows from the Grande Ronde Basalt of the Columbia River Basalt Group include several with the chemical composition of ferro-andesites. These flows have SiO, > 55%, MgO < 4 % , and also have higher FeIMg than the average value for Grande Ronde Basalt. They are also distinctly richer in Cs, Rb, K, Ba, La, Ce, Th, and U than the remainder of the Grande Ronde Basalt flows, and possess small negative Eu anomalies. Their Pb isotopic compositions define a mixing line with a negative slope on a 206Pb/204Pb versus 207Pb/204Pb plot. Their Nd isotopic compositions lie between 143Nd/'44Nd = 0.51252 and 0.51264, and their Sr isotopic compositions lie between 87Sr/86Sr = 0.7055 and 0.7060. These values define the enriched end of the Columbia River Basalt Group spectrum on a Sr-Nd epsilon diagram (excluding the Saddle Mountains Basalt). These ferro-andesite flows also form a compositional end member of the Columbia River Basalt Group and are sufficiently distinctive to warrant special consideration. We compare them with lavas from other tholeiitic provinces. Petrogenetically, they can be related to the Grande Ronde Basalt low-Mg basalts by plagioclase fractionation, or by clinopyroxene fractionation in partially melted eclogites. However, the situation may not be that simple, as their unique isotopic compositions are closely related to those of parental mantle materials, perhaps thus requiring separate reservoirs and (or) sources. Extending this argument to other parts of the Columbia River Basalt Group suggests that the origin of these basalts may be in a system of comparatively small magma chambers in the uppermost mantle, frequently replenished from a variety of sources.RburnC : Plusieurs coulkes du Basalte de la Grande Ronde, qui est affilit au Groupe de Basalte de la Columbia River, ont la composition chimique des ferro-andksites. Ces coulkes ont des teneurs de Si02 > 55 %, MgO < 4 % , et des rapports Fe/Mg plus klevks que le rapport moyen fourni par le Basalte de la Grande Ronde. En outre, elles sont nettement plus riches en Cs, Rb, K, Ba, La, Ce, Th et U que tout le reste des coul6es de Basalte de la Grande Ronde, et elles affichent de faibles anomalies nkgatives en Eu. Leurs compositions isotopiques du Pb dtfinissent une droite de mklange avec une pente nkgative sur le diagramme 206Pb/2"Pb versus 207~b/204Pb. Leurs compositions isotopiques du Nd sont comprises entre 143Nd/'44Nd = 0,51252 et 0,51264, et leurs compositions isotopiques du Sr varient de 87Sr/86Sr = 0,7055 B 0,7060. Ces donnkes dkterminent le p61e enrichi de la courbe du Groupe de Basalte de la Columbia River dans le diagramrne epsilon Sr-Nd (excluant le Basalte de Saddle Mountains). Ces coulkes de ferro-andksite dtfinissent aussi un pBle chimique du Groupe de Basalte de la Columbia River, et elles sont suffisamment distinctes pour Ctre prises en considkration. Nous les comparons avec les laves de d'autres provinces tholtiitiques. Pktrogknktiquement, elles peuvent &tre relikes aux coulkes appauvries en Mg du Basalte de la Grande Ronde, soit par le fractionn...

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Klamath-Blue Mountain lineament, Oregon

Cited by 48 publications

References 0 publications

Extent of partial melting beneath the Cascade Range, Oregon: Constraints from gravity anomalies and ideal‐body theory

Extent of partial melting beneath the Cascade Range, Oregon: Constraints from gravity anomalies and ideal‐body theory

Central Cascadia subduction zone creep

Ferro-andesites in the Grande Ronde Basalt: their composition and significance in studies of the origin of the Columbia River Basalt Group

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