Petrology and geochemistry of Cambrian volcanic rocks from the Avalon Peninsula, Newfoundland

1985 ◽  
Vol 22 (11) ◽  
pp. 1594-1601 ◽  
Author(s):  
John D. Greenough ◽  
V. S. Papezik
Keyword(s):  
High Pressures ◽  
Volcanic Rocks ◽  
Flood Basalts ◽  
Alkali Basalts ◽  
Middle Cambrian ◽  
Ti Oxides ◽  
Incompatible Elements ◽  
Petrology And Geochemistry ◽  
High Concentrations ◽  
Avalon Peninsula

Middle Cambrian basaltic flows, lapilli tuffs, and their feeder pipes, on the Avalon Peninsula, Newfoundland, show high Nb/Y and low Zr/Nb ratios and high concentrations of incompatible elements, such as Nb and Zr, which are typical of alkaline rocks. The compositions of relict clinopyroxenes are consistent with these conclusions. Relatively low Mg′ values and low CaO and high TiO2 concentrations show that the flows represent evolved compositions. Petrographic evidence and trends in trace-element data indicate that the range of bulk-rock compositions in the feeder pipes can be related to precipitation of augite, plagioclase, and olivine as well as late removal of Fe–Ti oxides and apatite. The negative correlation (shown by noncumulus rocks) between Mg′ and Al2O3, the relatively high Mg′ values of the flows, and the alkaline nature of the rocks distinguish them from most flood basalts and relate them to rift basalts. Low Al2O3 concentrations at the highest Mg′ values may be related to genesis in a garnet-rich mantle source under high pressures. These continental alkali basalts provide evidence that this portion of Avalonian terrane experienced tension during the Cambrian.

Petrology and geochemistry of Cambrian volcanic rocks from the Avalon Zone in New Brunswick

1985 ◽  
Vol 22 (6) ◽  
pp. 881-892 ◽  
Author(s):  
John D. Greenough ◽  
S. R. McCutcheon ◽  
V. S. Papezik
Keyword(s):  
New Brunswick ◽  
Volcanic Rocks ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Middle Cambrian ◽  
Mafic Rocks ◽  
Rock Types ◽  
Petrology And Geochemistry ◽  
Eastern Seaboard ◽  
Highly Evolved

Lower to Middle Cambrian volcanic rocks occur within the Avalon Zone of southern New Brunswick at Beaver Harbour and in the Long Reach area. The Beaver Harbour rocks are intensely altered, but the major- and trace-element geochemistry indicates that they could be highly evolved (basaltic andesites) within-plate basalts. The mafic flows from the Long Reach area form two chemically and petrologically distinct groups: (1) basalts with feldspar phenocrysts that represent evolved continental tholeiites with some oceanic characteristics; and (2) a group of aphyric basalts showing extremely primitive continental tholeiite compositions, also with oceanic affinities and resembling some rift-related Jurassic basalts on the eastern seaboard. Felsic pyroclastic rocks in the Long Reach area make the suite bimodal. This distribution of rock types supports conclusions from the mafic rocks that the area experienced tension throughout the Early to Middle Cambrian.

Essential Characteristics of Volcanic Rocks of Yixian Formation and Discussion on Tectonic Setting in Chaoyang Basin, Western Liaoning

2012 ◽  
Vol 170-173 ◽  
pp. 1261-1264
Author(s):  
Yan Dong Peng ◽  
De He Xing
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Yixian Formation ◽  
Western Liaoning ◽  
Incompatible Elements ◽  
High K ◽  
Petrology And Geochemistry ◽  
Bottom To Top ◽  
Compatible Elements ◽  
Comprehensive Study

Volcanic rocks of Early Cretaceous Yixian Formation were widely distributed in western Liaoning. The Yixian Formation in the Chaoyang basin can be divided into two subcycles from bottom to top. The first subcycle is composed of basalt, basalt andesite and andesite. The second subcycle is composed of trachyandensite and trachyte. The volcanic rocks are characterized by high SiO2, Al2O3, K2O and Na2O, and comparatively low TiO2 components. The volcanic rocks are obviously enriched in incompatible elements (K, Rb, Sr, Zr, Ba, Pb, Li etc.), and depleted in compatible elements (Co, Ni, Cr, V etc.). The volcanic rocks are rich in LREE. There is a slight low Eu negative abnormality and low Ce negative abnormality. Based on t he studies of petrology and geochemistry, volcanic rocks of Yixian Formation belong to the high-K calc-alkaline magmatic serious. Comprehensive study of regional structures and geochemistry of volcanic rocks, the volcanic rocks of Yixian Formation were generated in the environment of lithosphere inhomogeneous extension, as a product of the intraplate orogeny of Yanshan Mountains.

Le terrane de Slide Mountain (Cordillères canadiennes) : une lithosphère océanique marquée par des points chauds

2003 ◽  
Vol 40 (6) ◽  
pp. 833-852 ◽  
Author(s):  
M Tardy ◽  
H Lapierre ◽  
D Bosch ◽  
A Cadoux ◽  
A Narros ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Oceanic Island ◽  
Light Rare Earth ◽  
Isotopic Compositions ◽  
Incompatible Elements ◽  
Depleted Mantle ◽  
Mantle Sources ◽  
British Colombia ◽  
Ultramafic Cumulates ◽  
Back Arc

The Slide Mountain Terrane consists of Devonian to Permian siliceous and detrital sediments in which are interbedded basalts and dolerites. Locally, ultramafic cumulates intrude these sediments. The Slide Mountain Terrane is considered to represent a back-arc basin related to the Quesnellia Paleozoic arc-terrane. However, the Slide Mountain mafic volcanic rocks exposed in central British Colombia do not exhibit features of back-arc basin basalts (BABB) but those of mid-oceanic ridge (MORB) and oceanic island (OIB) basalts. The N-MORB-type volcanic rocks are characterized by light rare-earth element (LREE)-depleted patterns, La/Nb ratios ranging between 1 and 2. Moreover, their Nd and Pb isotopic compositions suggest that they derived from a depleted mantle source. The within-plate basalts differ from those of MORB affinity by LREE-enriched patterns; higher TiO2, Nb, Ta, and Th abundances; lower εNd values; and correlatively higher isotopic Pb ratios. The Nd and Pb isotopic compositions of the ultramafic cumulates are similar to those of MORB-type volcanic rocks. The correlations between εNd and incompatible elements suggest that part of the Slide Mountain volcanic rocks derive from the mixing of two mantle sources: a depleted N-MORB type and an enriched OIB type. This indicates that some volcanic rocks of the Slide Mountain basin likely developed from a ridge-centered or near-ridge hotspot. The activity of this hotspot is probably related to the worldwide important mantle plume activity that occurred at the end of Permian times, notably in Siberia.

Isotopically depleted, alkalic lavas from Bowie Seamount, northeast Pacific Ocean

1988 ◽  
Vol 25 (10) ◽  
pp. 1708-1716 ◽  
Author(s):  
Brian L. Cousens
Keyword(s):  
Gulf Of Alaska ◽  
Small Degree ◽  
Geochemical Data ◽  
Alkali Basalts ◽  
Sea Floor ◽  
Queen Charlotte Islands ◽  
Incompatible Elements ◽  
Depleted Mantle ◽  
Partial Melts ◽  
Enrichment Process

Bowie Seamount, located 200 km west of the Queen Charlotte Islands, British Columbia, is one of the southernmost of the Pratt–Welker Seamounts in the Gulf of Alaska. Eight dredge hauls recovered hawaiite and mugearite, with major-and trace-element compositions similar to those of Hawaiian alkali basalts. All samples are enriched in light incompatible elements but are isotopically MORB-like: 87Sr/86Sr = 0.70269–0.70285; 143Nd/144Nd = 0.51307–0.51315; and 206Pb/204Pb = 18.26–19.18. Sr- and Pb-isotope ratios correlate positively, whereas Sr and Nd correlate negatively, and lie on a mixing trend between DMM and HIMU mantle components. Juan de Fuca MORB have similar ratios and define similar mixing trends.The combined geochemical data require that the mantle source of Bowie (and Pratt–Welker) magmas has only recently been enriched in incompatible elements. The enrichment process could involve (i) metasomatism of the underlying lithosphere by CO2-rich fluids from a depleted source or (ii) mixing of silicate melts from a HIMU source with small-degree partial melts from depleted mantle. Alternatively, the magmas may be partial melts of subducted, 1.2 Ga oceanic crust that was variably enriched in U and Sr(?) during sea-floor alteration.

A Discussion on volcanism and the structure of the Earth - Proposals concerning the variation of volcanic products and processes within the oceanic environment

1972 ◽  
Vol 271 (1213) ◽  
pp. 131-140 ◽  
Keyword(s):  
Structural Model ◽  
Early Stage ◽  
Volcanic Rocks ◽  
Fracture Zones ◽  
Sea Floor ◽  
Stage Of Development ◽  
Incompatible Elements ◽  
The Earth ◽  
Sea Floor Spreading ◽  
Low Pressures

An attempt is made to fit available petrochemical data on oceanic volcanic rocks into the structural model for the ocean basins presented by the plate tectonic theory. It is suggested that there are three major volcanic regimes: (i) the low-potassic olivine tholeiite association of the axial zones of the oceanic ridges where magmatic liquids are generated at low pressures high in the mantle, (ii) the alkalic (Na > K) associations along linear fractures where liquids generated at greater depth gain easy egress to the surface, (iii) those alkalic associations, rich in incompatible elements, of island groups, remote from fracture zones, where magmas created at depth proceed slowly to the surface and in consequence suffer intense fractionation. There are certain discrepancies in this pattern, notably that there is no apparent relation between rate of sea-floor spreading and degree of over-saturation of the axial zone basalts and that certain areas, such as Iceland, are characterized by excess volcanism. Explanation of these anomalies is sought by examining an oceanic area in an early stage of development—the Red Sea. It is tentatively suggested that the initial split of a contiguous continent might be brought about by the linking of profound fractures, caused by domal uplift related to rising isolated lithothermal systems, and that the present anomalies in oceanic volcanism may reflect the variation in rate of thermal convection within the original isolated lithothermal plumes.

scholarly journals High pressures increase α-chymotrypsin enzyme activity under perchlorate stress

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Stewart Gault ◽  
Michel W. Jaworek ◽  
Roland Winter ◽  
Charles S. Cockell
Keyword(s):  
High Pressure ◽  
Enzyme Activity ◽  
Phase Space ◽  
High Pressures ◽  
Extreme Environments ◽  
Combined Effects ◽  
Deep Subsurface ◽  
Subsurface Environments ◽  
Dissolved Ions ◽  
High Concentrations

Abstract Deep subsurface environments can harbour high concentrations of dissolved ions, yet we know little about how this shapes the conditions for life. We know even less about how the combined effects of high pressure influence the way in which ions constrain the possibilities for life. One such ion is perchlorate, which is found in extreme environments on Earth and pervasively on Mars. We investigated the interactions of high pressure and high perchlorate concentrations on enzymatic activity. We demonstrate that high pressures increase α-chymotrypsin enzyme activity even in the presence of high perchlorate concentrations. Perchlorate salts were shown to shift the folded α-chymotrypsin phase space to lower temperatures and pressures. The results presented here may suggest that high pressures increase the habitability of environments under perchlorate stress. Therefore, deep subsurface environments that combine these stressors, potentially including the subsurface of Mars, may be more habitable than previously thought.

Geochemistry of Siluro-Devonian Tobique volcanic belt in northern and central New Brunswick (Canada): tectonic implications

1989 ◽  
Vol 26 (6) ◽  
pp. 1282-1296 ◽  
Author(s):  
J. Dostal ◽  
R. A. Wilson ◽  
J. D. Keppie
Keyword(s):  
New Brunswick ◽  
Mantle Source ◽  
Upper Mantle ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Continental Rift ◽  
Basaltic Rocks ◽  
Incompatible Elements ◽  
Tectonic Implications

Siluro-Devonian volcanic rocks of the northwestern mainland Appalachians are found mainly in the Tobique belt of New Brunswick where they consist predominantly of bimodal mafic–felsic suites erupted in a continental-rift environment. The axis of the Tobique rift trends north-northeast – south-southwest, obliquely to the regional northeast–southwest trend of the Appalachians. These geometric relationships are interpreted as being the result of rifting in a sinistral shear regime produced during emplacement of the Avalon terrene. The basaltic rocks are continental tholeiites and transitional basalts derived from a heterogeneous upper-mantle source that was enriched in incompatible elements relative to the primordial mantle. The mantle source was probably affected by the subduction processes.

Cambrian trilobites in central Newfoundland volcanic belt

1968 ◽  
Vol 105 (4) ◽  
pp. 372-377 ◽  
Author(s):  
Marshall Kay ◽  
Niles Eldredge
Keyword(s):  
North America ◽  
New World ◽  
Volcanic Rocks ◽  
Volcanic Belt ◽  
Middle Cambrian ◽  
Atlantic Province ◽  
Volcanic Belts

SUMMARYThe discovery of species of Kootenia and Bailiella known from the Middle Cambrian of western Newfoundland (“Pacific Province”) and southeastern Newfoundland (“Atlantic Province”) in limestone within volcanic rocks near New World Island, eastern Notre Dame Bay, is the first demonstration of the presence of Cambrian in the volcanic belts in North America, and also shows the mixing of forms from the two provinces.

Evolution of deep mantle sourced carbonated melt in the mantle lithosphere

2020 ◽  
Author(s):  
Guoliang Zhang
Keyword(s):  
Rare Earth ◽  
Field Strength ◽  
Rare Earth Elements ◽  
Lithospheric Mantle ◽  
High Field ◽  
Volcanic Rocks ◽  
Mantle Lithosphere ◽  
High Field Strength ◽  
Alkali Basalts ◽  
Deep Mantle

<p>Deep sourced magmas play a key role in distribution of carbon in the Earth’s system. Oceanic hotspots rooted in deep mantle usually produce CO<sub>2</sub>-rich magmas. However, the association of CO<sub>2</sub> with the origin of these magmas remains unclear. Here we report geochemical analyses of a suite of volcanic rocks from the Caroline Seamount Chain formed by the deep-rooted Caroline hotspot in the western Pacific. The most primitive magmas have depletion of SiO<sub>2</sub> and high field strength elements and enrichment of rare earth elements that are in concert with mantle-derived primary carbonated melts. The carbonated melts show compositional variations that indicate reactive evolution within the overlying mantle lithosphere and obtained depleted components from the lithospheric mantle. The carbonated melts were de-carbonated and modified to oceanic alkali basalts by precipitation of perovskite, apatite and ilmenite that significantly decreased the concentrations of rare earth elements and high field strength elements. These magmas experienced a stage of non-reactive fractional crystallization after the reactive evolution was completed. Thus, the carbonated melts would experience two stages, reactive and un-reactive, of evolution during their transport through in thick oceanic lithospheric mantle. We suggest that the mantle lithosphere plays a key role in de-carbonation and conversion of deep-sourced carbonated melts to alkali basalts. This work was financially supported by the National Natural Science Foundation of China (91858206, 41876040).</p>

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