scholarly journals Protracted magmatism and magnetization around the McClure Mountain alkaline igneous complex

Lithosphere ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 590-602
Author(s):  
Anthony F. Pivarunas ◽  
Joseph G. Meert
Keyword(s):  
Nepheline Syenite ◽  
Paleomagnetic Data ◽  
Early Cambrian ◽  
Igneous Complex ◽  
Dike Intrusion ◽  
Western Side ◽  
Host Rocks

Abstract The McClure Mountain–Iron Mountain igneous complex is an alkalic intrusive center in the northern Wet Mountains of southern Colorado. It was emplaced in early Cambrian time into gneissic/granitic 1.75–1.45 Ga Proterozoic host rocks. Numerous dikes are associated with the complex, primarily along the western side. Although the main intrusive nepheline-syenite body is well dated, the ages of the surrounding dikes are poorly known. Crosscutting relationships and poorly defined K-Ar dates suggest that the dikes are younger than the main intrusion. Paleomagnetic samples were collected from dikes associated with the McClure Mountain igneous complex. Geochronologic samples were also collected from two dikes sampled for their paleomagnetism. We obtained U-Pb zircon ages of 526 ± 8 Ma for a lamprophyric extracomplex dike and 483 ± 2 Ma for a trachytic extracomplex dike. These ages suggest either multistage or protracted dike intrusion around the ca. 524 Ma McClure Mountain complex. Our paleomagnetic data are consistent with previously published results. Dikes of the complex primarily exhibit southeast and shallow paleomagnetic directions, with variable declinations. Results from several baked contact tests indicate that the magnetizations are secondary. A steeply inclined magnetization is pervasive and was acquired over a protracted interval from late Laramide time to the present day.

scholarly journals Introduction to the special issue on the Flatreef PGE-Ni-Cu deposit, northern limb of the Bushveld Igneous Complex

2020 ◽  
Author(s):  
Wolfgang D. Maier ◽  
Marina Yudovskaya ◽  
Pedro Jugo
Keyword(s):  
Ore Deposits ◽  
Special Issue ◽  
Ore Formation ◽  
Igneous Complex ◽  
Northern Limb ◽  
Pge Mineralization ◽  
World Class ◽  
Bushveld Igneous Complex ◽  
Mine Development ◽  
Host Rocks

AbstractMore than 30 years ago, Cox and Singer (1986) suggested that magmatic platinum-group element (PGE)-Ni-Cu deposits are amongst the best understood of ore deposits, yet the origin of PGE mineralization in the Bushveld Igneous Complex (BIC) remains controversial after a century of study. In the northern limb of the BIC, the unravelling of ore formation proved particularly difficult due to relatively poor outcrop, which is typically affected by contamination of the intruding magmas with the host rocks and expressed in the form of abundant xenoliths, footwall rafts and disturbance of magmatic stratigraphy. In this thematic issue, we present contributions on the Flatreef, a recently discovered world-class PGE-Ni-Cu deposit constituting a downdip extension of the mineralized unit of the Platreef of the northern limb. Two deep shafts are currently being sunk, making the Flatreef one of the most significant new mine development on the Bushveld in several decades.

scholarly journals Britholite Group Minerals from REE-Rich Lithologies of Keivy Alkali Granite—Nepheline Syenite Complex, Kola Peninsula, NW Russia

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 732 ◽  
Author(s):  
Dmitry Zozulya ◽  
Lyudmila Lyalina ◽  
Ray Macdonald ◽  
Bogusław Bagiński ◽  
Yevgeny Savchenko ◽  
...  
Keyword(s):  
Kola Peninsula ◽  
Nepheline Syenite ◽  
Full Range ◽  
Economic Importance ◽  
Alkali Granite ◽  
Granitic Magma ◽  
High Co2 ◽  
Low Co2 ◽  
Chemical Studies ◽  
Host Rocks

The Keivy alkali granite-nepheline syenite complex, Kola Peninsula, NW Russia, contains numerous associated Zr-REE-Y-Nb occurrences and deposits, formed by a complex sequence of magmatic, late-magmatic, and post-magmatic (including pegmatitic, hydrothermal, and metasomatic) processes. The REE-rich lithologies have abundant (some of economic importance) and diverse britholite group minerals. The REE and actinides distribution in host rocks indicates that the emanating fluids were alkaline, with significant amounts of F and CO2. From chemical studies (REE and F variations) of the britholites the possible fluid compositions in different lithologies are proposed. Fluorbritholite-(Y) and britholite-(Y) from products of alkali granite (mineralized granite, pegmatite, quartzolite) formed under relatively high F activity in fluids with low CO2/H2O ratio. The highest F and moderate CO2 contents are characteristic of fluid from a mineralized nepheline syenite, resulting in crystallization of fluorbritholite-(Ce). Britholite group minerals (mainly fluorcalciobritholite and ‘calciobritholite’) from a nepheline syenite pegmatite formed from a fluid with composition changing from low F and high CO2 to moderate F and CO2. An extremely high F content is revealed for metasomatizing fluids emanating from alkali granitic magma and which affected the basic country rocks. The dominant substitution scheme for Keivy britholites is REE3+ + Si4+ = Ca2+ + P5+, showing the full range of ‘britholite’ and ‘calciobritholite’ compositions up to theoretical apatite.

Identification and isotopic studies of early Cambrian magmatism (El Carancho Igneous Complex) at the boundary between Pampia terrane and the Río de la Plata craton, La Pampa province, Argentina

2012 ◽  
Vol 21 (2-3) ◽  
pp. 378-393 ◽  
Author(s):  
Carlos J. Chernicoff ◽  
Eduardo O. Zappettini ◽  
João O.S. Santos ◽  
Marta C. Godeas ◽  
E. Belousova ◽  
...  
Keyword(s):  
Early Cambrian ◽  
Rio De La Plata ◽  
Río De La Plata ◽  
Igneous Complex ◽  
La Plata ◽  
Isotopic Studies

Rb-Sr age determinations of rocks from the Okenyenya igneous complex, northwestern Namibia

1993 ◽  
Vol 130 (3) ◽  
pp. 335-343 ◽  
Author(s):  
Simon C. Milner ◽  
Anton P. Le Roex ◽  
Ronald T. Watkins
Keyword(s):  
Nepheline Syenite ◽  
The South ◽  
Major Phase ◽  
Igneous Complex ◽  
Linear Feature ◽  
The North ◽  
Pan African ◽  
Structural Discontinuity ◽  
Younger Age ◽  
Northern Edge

AbstractThe Okenyenya igneous complex is one of a suite of intrusions which define a prominent northeast-trending linear feature in Damaraland, northwestern Namibia. Precise Rb–Sr internal isochron ages range from 128.6 ± 1 to 123.4 ± 1.4 Ma for the major phases of intrusion identified within the complex. The tholeiitic gabbros forming the outer rings of the complex, and the later alkali gabbros which form the central hills, cannot be distinguished in terms of Rb–Sr ages, although field relations clearly indicate the younger age of the latter. The intrusionsof nepheline-syenite and essexite comprising the mountain of Okenyenya Bergon the northern edge of the complex give ages of 123.4 ± 1.4 and 126.3 ± 1 Ma, respectively, and form the final major phase of intrusion. The ages obtained for early and late intrusive phases define a minimum magmatic ‘life-span’ of approximately 5 Ma for the complex. The determined age of the Okenyenya igneous complex (129–123 Ma), when taken together with the few reliable published ages for other Damaraland complexes (130–134 Ma), suggests that these sub-volcanic complexes were emplaced contemporaneously with the widespread Etendeka volcanics (˜ 130 Ma), and relate to magmatism associated with the breakup of southern Africa and South America with the opening of the South Atlantic Ocean. The linear distributionof intrusions in Damaraland is interpreted to be due to magmatism resultingfrom the upwelling Tristan plume being focused along a structural discontinuity between the Pan-African, Damaran terrain to the south, and Proterozoiccratonic basement to the north.

scholarly journals On the applicability of magnetic prospecting for chromite in the Fiskenæsset region, West Greenland

1969 ◽  
Vol 20 ◽  
pp. 1-25
Author(s):  
M Ghisler ◽  
P.V Sharma
Keyword(s):  
Magnetic Measurements ◽  
Aeromagnetic Survey ◽  
Igneous Complex ◽  
West Greenland ◽  
Rock Samples ◽  
Rock Types ◽  
Basement Gneiss ◽  
Host Rocks

The chromite deposits of the Fiskenæsset region belong to a metamorphosed igneous complex of stratiform type occurring in the basement gneiss unit of older Precambrian age in West Greenland. Short descriptions and modal compositions of the different rock types are given together with the results of magnetic measurements on 60 rock samples (data shown in tables 1-5). On the basis of known geology and rock susceptibilities different models are discussed with respect to the applicability of both an airborne and a ground magnetometer survey. It is concluded that the susceptibility contrasts involved are sufficient for locating favourable host rocks by aeromagnetic survey, but direct magnetic prospecting for chromite horizons predominantly occurring within anorthosites may not be feasible.

Biostratigraphy, Age, and Paleoenvironment of the Pliocene Beaufort Formation on Meighen Island, Canadian Arctic Archipelago

2021 ◽  
Keyword(s):  
Sea Level ◽  
Marine Sediments ◽  
Canadian Arctic ◽  
Atmospheric Co2 ◽  
Paleomagnetic Data ◽  
Canadian Arctic Archipelago ◽  
Warm Climate ◽  
Western Side ◽  
Continuous Deposition

The Beaufort Formation records extraordinary details of Arctic environments and amplified temperatures at approximately modern levels of atmospheric CO2. It was deposited during the Neogene on the western side of what is now the Canadian Arctic Archipelago. Meighen Island is a key locality for studying this formation because marine sediments there are interbedded with terrestrial fossiliferous sands. The biostratigraphic succession, fossils from the marine beds, and paleomagnetic data from the Bjaere Bay region of the island suggest two potential ages for the studied exposures: either continuous deposition at ca. 3.0 Ma, or a sequence of deposits at ca. 4.5 Ma and 3.4 Ma. The sediments appear to encompass at least two eustatic highstands of sea level and a particularly warm climate interval of the Pliocene Arctic.

Features of paleohydrogeochemistry of the lower cambrian deposits of the Siberian Platform

2020 ◽  
Author(s):  
Anatoly V. Chernykh ◽  
◽  
Dmitry A. Tokarev ◽  
Dmitry A. Novikov ◽  
Fedor F. Dultsev ◽  
...  
Keyword(s):  
Calcium Chloride ◽  
Siberian Platform ◽  
Lower Cambrian ◽  
Early Cambrian ◽  
Potassium Salts ◽  
Modern Chemistry ◽  
Host Rocks

The results of paleohydrogeochemical reconstructions of the Lower Cambrian deposits of the Siberian platform are presented. The characteristic of the main biota groups of the Early Cambrian time of the Siberian paleobasin is given. The conditions of formation and compositional features of syngenetic waters are considered. The modern chemistry of the inter–salt brines is mainly of an inherited nature, while the appearance of super–strong brines of calcium chloride composition is due to the processes of deep interaction of the initial sea brine with the host rocks. Based on the analysis of the hydrogeochemical features of the Lower Cambrian sediments, the prediction of the zones of distribution of potassium salts is given.

HETEROGENEITY OF S ISOTOPE COMPOSITIONS RECORDED IN THE SUDBURY IGNEOUS COMPLEX, CANADA: SIGNIFICANCE TO FORMATION OF Ni-Cu SULFIDE ORES AND THE HOST ROCKS

2015 ◽  
Vol 110 (4) ◽  
pp. 1125-1135 ◽  
Author(s):  
E. M. Ripley ◽  
P. C. Lightfoot ◽  
E. C. Stifter ◽  
B. Underwood ◽  
V. Taranovic ◽  
...  
Keyword(s):  
Sulfide Ores ◽  
Igneous Complex ◽  
Sudbury Igneous Complex ◽  
Host Rocks ◽  
S Isotope

New high-quality paleomagnetic data from the Borborema Province (NE Brazil): Refinement of the APW path of Gondwana in the Early Cambrian

2021 ◽  
Vol 360 ◽  
pp. 106243
Author(s):  
Paul Yves Jean Antonio ◽  
Ricardo Ivan Ferreira Trindade ◽  
Bruno Giacomini ◽  
Daniele Brandt ◽  
Eric Tohver
Keyword(s):  
Paleomagnetic Data ◽  
Early Cambrian ◽  
High Quality ◽  
Borborema Province
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