Paleomagnetism of the Cambro-Ordovician McClure Mountain alkalic complex, Colorado

Lynnes, C.; Voo, Rob Van der

doi:10.1016/0012-821x(84)90062-1

Cited by 22 publications

(27 citation statements)

References 12 publications

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“…The McClure Mountain alkalic complex, which is cut by carbonatite dikes, intruded into lower Proterozoic metamorphic granitic and hornblende gneisses and amphibolites in the early Cambrian (Lynnes and Van Der Voo, 1984;Woolley, 1987), with K-Ar and Rb-Sr dating techniques giving ages ranging from 535 to 506 Ma (Woolley, 1987). Apatite fission track dates give a much younger age of 293 ± 62 Ma (Lynnes and Van Der Voo, 1984), suggesting alteration of the complex occurred ca. 300 Ma.…”

Section: Carbonatitesmentioning

confidence: 99%

Clumped isotope thermometry of carbonatites as an indicator of diagenetic alteration

Dennis

Schrag

2010

Geochimica et Cosmochimica Acta

269

279

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Section: Carbonatitesmentioning

confidence: 99%

Clumped isotope thermometry of carbonatites as an indicator of diagenetic alteration

Dennis

Schrag

2010

Geochimica et Cosmochimica Acta

269

279

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“…Colorado have been remagnetized in late Paleozoic time [Jackson et al, 1988;Lynnes and Van der Voo, 1984]. In the study by Dankers and Lapointe [1981], three sites were sampled in a single diabase dike.…”

Section: Lower Paleozoic Intrusions In Central New Mexico and Centralmentioning

confidence: 99%

Paleomagnetism of Latest Cambrian‐Early Ordovician and Latest Cretaceous‐Early Tertiary rocks of the Florida Mountains, southwest New Mexico

Geissman¹,

Jackson²,

Harlan³

et al. 1991

J. Geophys. Res.

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Paleomagnetic investigations have been carried out on latest Cambrian to Early Ordovician alkaline intrusions, their contact intermediate to mafic composition metaigneous rocks, and overlying lower Paleozoic and early Tertiary strata in the Florida Mountains, southwestern New Mexico. A well‐defined, predominantly normal polarity magnetization of high median destructive induction and high, usually discrete laboratory unblocking temperatures is isolated from sites in metaigneous rocks in contact with syenites exposed on the northwestern flank of this late Cenozoic uplift. Combinations of stable endpoint and planar data are used in data analysis at the site level (D = 262°, I = −30°, α95 = 10°, k = 12; N = 22 site means). In addition to the presence of reverse polarity magnetizations at two sites, the dispersion of site mean directions in these rocks (VGP angular standard deviation of 19.6°) suggests that considerable variation of the geomagnetic field has been averaged. After correction for a combination of early Tertiary (Laramide) deformation and late Tertiary Basin‐Range block tilting, this magnetization gives a paleomagnetic pole at 6°S, 169°E and is interpreted to have been acquired soon after intrusion of alkaline plutons at 503±10 Ma, based on published U‐Pb zircon isotopic age determinations. A lack of well‐defined, coherent magnetizations in the plutonic rocks may reflect the complex subsolidus alteration history of these rocks, as interpreted with Rb‐Sr isotopic data. Hematitic sandstones of the earliest Ordovician Bliss Formation, which directly overlie the crystalline rocks in portions of the range, give dual‐polarity magnetizations whose directions suggest that these rocks have probably been remagnetized; this remagnetization possibly occurred during deformation in late Cretaceous/Tertiary time. Ordovician carbonate rocks of the El Paso and Montoya formations give only a Holocene magnetization. Paleocene to earliest Eocene(?) hematite‐cemented clastic rocks of the Lobo Formation possess dual‐polarity magnetizations. The origin of their magnetization is difficult to assess with the available data. In total, however, paleomagnetic data from the Bliss and Lobo formations argue against any significant vertical axis rotation of the area since Laramide deformation ending in Early Tertiary time. The intermediate to mafic composition metaigneous rocks from the Florida Mountains provide a latest Cambrian‐Early Ordovician paleomagnetic pole that compares favorably with other North American paleopoles satisfying several acceptance criteria. The Florida Mountains data further support recent constructions of apparent polar wander paths for North America and thus the hypothesis that significant counterclockwise rotation of North America occurred during the Ordovician.

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“…12 in Dankers and Lapointe 1981). Poles A1 and A2 also lie near the "syenite" pole (18"N, 142"E), dated at 535 Ma from the Cambro-Ordovician McClure Mountain complex of Colorado (Lynnes and Van der Voo 1984). The four "northerly" ( -30°N) Ordovician poles (LP, MB, CR, J) are from Appalachian studies.…”

Section: Discussionmentioning

confidence: 97%

Ordovician paleomagnetic results from the St. George and Table Head carbonates of western Newfoundland

Deutsch¹,

Prasad²

1987

Can. J. Earth Sci.

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We have studied 85 limestone and dolostone samples from 21 sites of the St. George and Table Head groups (Lower and Middle Ordovician) on Port au Port Peninsula (Humber Zone). Their gentle (~15°) tilt is probably Devonian. A steep viscous component dominant in the natural remanence is removed by thermal and (less efficiently) alternating-field demagnetization. In about 60% of all samples, the thermal treatment yielded a southeasterly reverse component ("A"), which typically remained blocked to 450–500 °C and then decayed to noise. Mean A component directions calculated from Zijderveld plots and referred to bedding are D, I = 148.5°, +33.6 °for N = 9 St. George sites and D, I = 150.0°, I = +40.7 °for N = 5 Table Head sites. Corresponding antipoles are 17.5°N, 152.3°E, dp, dm = 2.8°, 4.9 °and 13.4°N, 149.2°E, dp, dm = 2.9°, 4.7°, respectively. We interpret these results as representative of the geomagnetic field in the Early and mid-Ordovician. In 14 samples, mainly from the older St. George strata, thermal treatment yielded a reverse ("B") component with mean direction D, I = 167.9°, −9.2°, corresponding to an antipole at 44.9°N, 138.2°E, dp, dm = 3.6°, 7.1°. We interpret this as a late Paleozoic overprint in diagenetic hematite. The 30° anticlockwise rotation of Newfoundland proposed by Wegener is not supported by our data.

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Paleomagnetism of the Cambro-Ordovician McClure Mountain alkalic complex, Colorado

Cited by 22 publications

References 12 publications

Clumped isotope thermometry of carbonatites as an indicator of diagenetic alteration

Clumped isotope thermometry of carbonatites as an indicator of diagenetic alteration

Paleomagnetism of Latest Cambrian‐Early Ordovician and Latest Cretaceous‐Early Tertiary rocks of the Florida Mountains, southwest New Mexico

Ordovician paleomagnetic results from the St. George and Table Head carbonates of western Newfoundland

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