Eocene Challis-Kamloops volcanism in central British Columbia: an example from the Buck Creek basin

1998 ◽  
Vol 35 (8) ◽  
pp. 951-963 ◽  
Author(s):  
J Dostal ◽  
D A Robichaud ◽  
B N Church ◽  
P H Reynolds
Keyword(s):  
British Columbia ◽  
Rare Earth ◽  
Rare Earth Element ◽  
Fractional Crystallization ◽  
Earth Element ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
The United States ◽  
Calc Alkaline ◽  
Heavy Rare Earth Element

Eocene volcanic rocks of the Buck Creek basin in central British Columbia are part of the Challis-Kamloops volcanic belt extending from the United States across British Columbia to central Yukon. The volcanic rocks include two units, the Buck Creek Formation, composed of high-K calc-alkaline rocks with predominant andesitic composition, and the overlying Swans Lake unit made up of intraplate tholeiitic basalts. Whole rock 40Ar/39Ar data for both units show that they were emplaced at 50 Ma. They have similar mantle-normalized trace element patterns characterized by a large-ion lithophile element enrichment and Nb-Ta depletion, similar chondrite-normalized rare earth element patterns with (La/Yb)n ~4-14 and heavy rare earth element fractionation, and overlapping epsilonNd values (2.4-3.1) and initial Sr-isotope ratios ( ~ 0.704). These features suggest derivation of these two units from a similar mantle source, probably garnet-bearing subcontinental lithosphere. The differences between tholeiitic and calc-alkaline suites can be due, in part, to differences in the depth of fractional crystallization and the crystallizing mineral assemblage. Fractional crystallization of the calc-alkaline magmas began at a greater (mid-crustal) depth and included fractionation of Fe-Ti oxides. The volcanic rocks are probably related to subduction of the Farallon plate under the North American continent in a regime characterized by transcurrent movements and strike-slip faulting.

Quantitative trace-element modelling of the crystallization history of the Kinojévis and Blake River groups, Abitibi Greenstone Belt, Ontario

1989 ◽  
Vol 26 (7) ◽  
pp. 1356-1367 ◽  
Author(s):  
A. D. Fowler ◽  
L. S. Jensen
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Fractional Crystallization ◽  
Earth Element ◽  
Calc Alkaline ◽  
Quantitative Modelling ◽  
Ti Oxides ◽  
History Of ◽  
High Level ◽  
Ree Patterns

The Archean tholeiitic Kinojévis suite is characterized by an iron-enrichment trend and abundant Fe–Ti oxides in its evolved basalts, andesites, and rhyolites. The rare-earth-element (REE) patterns of the suite remain flat from the basalts through to the rhyolites, with the development of small, negative Eu anomalies. Quantitative modelling of the trace elements from little-altered samples is consistent with the mineralogy, suggesting that the suite was produced through fractional crystallization of olivine, pyroxene, plagioclase, and Fe–Ti oxides. The evolved rhyolites are interpreted as having developed by greater than 90% fractional crystallization in a high-level magma chamber.The calc-alkaline Blake River Group conformably overlies the Kinojévis rocks and is characterized by enrichment in alkalis and silica. The REE patterns are light rare-earth-element (LREE) enriched, and the felsic rocks have prominent negative Eu anomalies. Geochemical modelling shows that the suite could have developed either through fractional crystallization dominated by plagioclase and clinopyroxene or by assimilation of tonalite, coupled with fractional crystallization.

scholarly journals The Jurassic–Early Cretaceous basalt–chert association in the ophiolites of the Ankara Mélange, east of Ankara, Turkey: age and geochemistry

2017 ◽  
Vol 155 (2) ◽  
pp. 451-478 ◽  
Author(s):  
VALERIO BORTOLOTTI ◽  
MARCO CHIARI ◽  
M. CEMAL GÖNCÜOGLU ◽  
GIANFRANCO PRINCIPI ◽  
EMILIO SACCANI ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Early Cretaceous ◽  
Middle Jurassic ◽  
Late Jurassic ◽  
Earth Element ◽  
Volcanic Rocks ◽  
Heavy Rare Earth Element ◽  
Rock Types ◽  
Ocean Ridge

AbstractThis study is focused on slide blocks including oceanic lavas associated with pelagic sediments within the eastern part of the Ankara Mélange. A detailed petrological characterization of the volcanic rocks and a detailed biochronological investigation of the associated radiolarian cherts in eight sections (east of Ankara) was carried out. The volcanic rocks are largely represented by basalts and minor ferrobasalts and trachytes. They show different geochemical affinities and overlapping ages including: (a) Late Jurassic – Early Cretaceous garnet-influenced MORB (middle late Oxfordian to late Kimmeridgian–early Tithonian and early–early late Tithonian; late Valanginian–early Barremian); (b) Early Cretaceous enriched-MORB (middle late Barremian–early early Aptian; Valanginian to middle Aptian–early Albian); (c) Middle Jurassic plume-type MORB (early–middle Bajocian to late Bathonian–early Callovian); (d) Late Jurassic – Early Cretaceous alkaline basalts (middle–late Oxfordian to late Kimmeridgian–early Tithonian; late Valanginian to late Hauterivian). All rock types show a clear garnet signature, as testified to by their high MREE/HREE (middle rare earth element/heavy rare earth element) ratios. The coexistence of chemically different rock types from Middle Jurassic to Early Cretaceous times suggests that they were formed in a mid-ocean ridge setting from partial melting of a highly heterogeneous mantle characterized by the extensive occurrence of OIB-metasomatized portions, which were likely inherited from Triassic mantle plume activity associated with the continental rift and opening of the Neotethys branch.

Rare-earth crystal chemistry of thalénite-(Y) from different environments

2018 ◽  
Vol 82 (2) ◽  
pp. 313-327
Author(s):  
Markus B. Raschke ◽  
Evan J. D. Anderson ◽  
Jason Van Fosson ◽  
Julien M. Allaz ◽  
Joseph R. Smyth ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Spatial Scales ◽  
Structure Refinement ◽  
X Ray Diffraction ◽  
Heavy Rare Earth ◽  
Heavy Rare Earth Element ◽  
X Ray ◽  
Golden Horn

ABSTRACTThalénite-(Y), ideally Y3Si3O10F, is a heavy-rare-earth-rich silicate phase occurring in granite pegmatites that may help to illustrate rare-earth element (REE) chemistry and behaviour in natural systems. The crystal structure and mineral chemistry of thalénite-(Y) were analysed by electron microprobe analysis, X-ray diffraction and micro-Raman spectroscopy from a new locality in the peralkaline granite of the Golden Horn batholith, Okanogan County, Washington State, USA, in comparison with new analyses from the White Cloud pegmatite in the Pikes Peak batholith, Colorado, USA. The Golden Horn thalénite-(Y) occurs as late-stage sub-millimetre euhedral bladed transparent crystals in small miarolitic cavities in an arfvedsonite-bearing biotite granite. It exhibits growth zoning with distinct heavy-rare-earth element (HREE) vs. light-rare-earth element (LREE) enriched zones. The White Cloud thalénite-(Y) occurs in two distinct anhedral and botryoidal crystal habits of mostly homogenous composition. In addition, minor secondary thalénite-(Y) is recognized by its distinct Yb-rich composition (up to 0.8 atoms per formula unit (apfu) Yb). Single-crystal X-ray diffraction analysis and structure refinement reveals Y-site ordering with preferential HREE occupation of Y2 vs. Y1 and Y3 REE sites. Chondrite normalization shows continuous enrichment of HREE in White Cloud thalénite-(Y), in contrast to Golden Horn thalénite-(Y) with a slight depletion of the heaviest REE (Tm, Yb and Lu). The results suggest a hydrothermal origin of the Golden Horn miarolitic thalénite-(Y), compared to a combination of both primary magmatic followed by hydrothermal processes responsible for the multiple generations over a range of spatial scales in White Cloud thalénite-(Y).

Geology and geochemistry of Huronian rhyolites and low-Ti continental tholeiites from the Thessalon region, central Ontario

1987 ◽  
Vol 24 (7) ◽  
pp. 1360-1385 ◽  
Author(s):  
Wayne T. Jolly
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Magma Mixing ◽  
Mantle Metasomatism ◽  
Granitic Rocks ◽  
Heavy Rare Earth Element ◽  
Tonalitic Gneiss ◽  
Oceanic Basalts ◽  
Low K

Bimodal volcanism associated with early phases of Huronian rifting in central Ontario, dated about 2450 Ma, produced low-Ti tholeiitic basalts and two varieties of crustally derived calc-alkaline rhyolite. Early tholeiites are characteristically highly evolved, have Mg* values from 30 to 50, and display pronounced enrichment in large-ion lithophile elements (LILE) and light rare-earth element (LREE) in comparison with modern oceanic basalts, fractionated heavy rare-earth element (HREE) patterns, and low Ti, Zr, P, Nb, Ba, and K abundances. Ti/Zr ratios rise progressively in early basalts and associated basaltic andesite fractionates from about 35 in early flows to 55 in central units. Late basalts also carry enriched LILE and LREE, but, in contrast to early types, have average Mg* values greater than 50 and lower rare-earth element (REE) abundances with flat HREE patterns. They also display negative Ba, Nb, and P anomalies on chondrite-normalized distribution diagrams, but lack low K, Zr, and Ti contents. Their Ti/Zr ratios of about 80 approach chondritic levels. Melting models suggest the differences are explained by lower degrees of fusion (as low as 10%) in a hydrated, LILE- and LREE-enriched peridotite during generation of the early basalts, leaving a residue containing appreciable garnet, amphibole, Ti oxides, zircon, and apatite.Erupted simultaneously with the basalts were two distinctive rhyolite types: (1) a low-LILE, high-LREE group (25% of analysed specimens), derived by −20% melting of granulitic siliceous tonalitic gneiss, presumably at deep crustal levels, and (2) a high-LILE, low-LREE group (75%), derived, probably at shallower levels, by ≤ 30% melting in granitic rocks with pegmatitic or leucogranitic compositions. Mutual magma mixing of basalts and rhyolites during early stages of volcanism produced abundant hybrid andesites, but the frequency of contamination is much lower in later units.Hypothetical subcontinental source compositions, calculated from the Raleigh equation, suggest that the Huronian mantle had already undergone a complex history. Low Ba, Nb, P, Ti, and depleted HREE abundances compared with abundances for modern oceanic basalts suggest that a basaltic melt had already been withdrawn from this source during Archean time. Subsequently, an episode of hydrous metasomatism enriched the source in LILE and LREE. The latter event resulted from (1) subcontinental mantle metasomatism by previous Archean subduction, (2) mantle metasomatism during the terminal Archean Kenoran Orogeny, or (3) a wave of hydrous metasomatism accompanying Huronian mantle convection immediately preceding volcanism.

Rare earth element concentrations in Quaternary volcanic rocks of southwestern British Columbia

1984 ◽  
Vol 21 (6) ◽  
pp. 731-736 ◽  
Author(s):  
Nathan L. Green ◽  
Paul Henderson
Keyword(s):  
British Columbia ◽  
Earth Element ◽  
Volcanic Rocks ◽  
Crustal Contamination ◽  
Lake Area ◽  
Calc Alkaline ◽  
Lower Light ◽  
The Individual ◽  
High Level ◽  
Ree Patterns

A suite of hy-normative hawaiites, ne-normative mugearite, and calc-alkaline andesitic rocks from the Garibaldi Lake area exhibits fractionated, slightly concave-upward REE patterns (CeN/YbN = 4.5–15), heavy REE contents about 5–10 times the chondritic abundances, and no Eu anomalies. It is unlikely that the REE patterns provide information concerning partial melting conditions beneath southwestern British Columbia because they have probably been modified substantially by upper crustal processes including crustal contamination and (or) crystal fractionation. The REE contents of the Garibaldi Lake lavas are not incompatible with previous interpretations that (1) the hawaiites have undergone considerable fractionation of olivine, plagioclase, and clinopyroxene; and (2) the individual andesitic suites were derived from separate batches of chemically distinct magma that evolved along different high-level crystallization trends. In general, however, the andesites are characterized by lower light REE contents than the basaltic andesites. These differences in LREE abundances may reflect different amounts of LREE-rich accessory phases, such as apatite, sphene, or allanite, assimilated from the underlying quartz diorites.

scholarly journals Petrogenesis of Heavy Rare Earth Element Enriched Rhyolite: Source and Magmatic Evolution of the Round Top Laccolith, Trans-Pecos, Texas

Minerals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 423 ◽  
Author(s):  
Brent Elliott
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Geochemical Evolution ◽  
Magmatic Differentiation ◽  
Magmatic System ◽  
Heavy Rare Earth ◽  
Heavy Rare Earth Element ◽  
Element Concentrations ◽  
Stage Crystallization

The Round Top rhyolite located in Trans-Pecos Texas is enriched in Be, F, Li, Nb, Rb, Sn, Th, U, Y, Zr, and rare earth elements (REEs). REE-bearing minerals are mainly ubiquitous nano-scale accessory phases throughout the groundmass, incorporated in synchysite-group minerals, xenotime-(Y), Y- and Ce-rich fluorite, and zircon. The rhyolite is peraluminous, high-silica, alkaline (not peralkaline), with elevated heavy rare earth element concentrations and anonymously negative Eu values. Pervasive spongy groundmass and recrystallization textures are consistent with the elevated and remobilized Zr, Th, and Y + HREE (heavy rare earth element) concentrations and a high field strength element (HFSE) soluble, sub-alkalic, F-rich, magmatic system. REE-bearing minerals are present as late-magmatic, interstitial phases and attributed with closed-system, post-magmatic, hydrothermal alteration. Petrogenetic modeling provides scenarios that explain the geochemical evolution and REE complexing behavior in evolved rhyolite magmas, and determines possible source compositions and evolution. Trace element models suggest a system typical of having extensive magmatic differentiation. The resulting rhyolite magma is indicative of a silica-rich magmatic system enriched in H2O, Li, and/or F that could be considered transitional between pure silicate melt and hydrothermal fluid, where fluorine-ligand complexing was prevalent through late magmatic cooling and crystallization processes. Thorough differentiation and high fluorine activity contributed to the late stage crystallization of REE-bearing minerals in the Round Top rhyolite.

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