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The Huronian sequence (Lower Proterozoicl. north of Lake Huron, contains tillites and abundant fine-grained sedimentary rocks. Analyses of rare earth elements (REE) in the matrix of tillite samples from the Gowganda Formation (~ 2.3 Gal is considered to be a reasonable estimate of upper crustal REE abundances for the region north of Lake Huron at the time of Gowganda deposition. The average is characterized by a moderately steep pattern (σLREEσHREE = 9.1) and a slight negative europium anomaly (). This pattern is similar to estimates of the composition of the surface of the Canadian Shield and is intermediate between estimates of typical Archean and post-Archean sedimentary rocks. REE patterns for framework granitoid clasts from the tillite suggest that K-rich granites, which were apparently unimportant in the formation of Archean sedimentary rocks, were abundant in the source regions of the Gowganda Formation. This may explain the intermediate nature of the Gowganda pattern.Comparison of the tillites and associated Gowganda mudstones suggests that previous estimates of upper crustal REE abundances, which were based on the analyses of fine-grained sedimentary rocks, may be systematically high. Relative distributions, however, are the same.Analyses of mudstones from the McKim. Pecors. Serpent Gowganda Lorrain and Gordon Lake Formations suggest rapid evolution in the composition of the exposed upper crust at the close of the Kenoran orogeny. REE patterns at the base of the Huronian are similar to typical Archean sedimentary rocks. REE characteristics change up section: patterns at the top resemble typical post-Archean sedimentary rocks.It is inferred that an essentially episodic change from an early exposed upper crust dominated by a tonalite-greenstone suite to one approximating granodioritic composition is recorded in Huronian sedimentary rocks. A deviation from the evolutionary trend of the Huronian, documented in the Gowganda Formation, may be related to the glacial origin of the Gowganda. 相似文献
14.
Changing trade patterns of the West Pacific 总被引:1,自引:0,他引:1
Donald W. Fryer 《GeoJournal》1980,4(5):479-484
In the enormous expansion of world trade in the quarter century after 1950, the share generated by countries of the Western Pacific remained remarkably constant. This relationship primarily reflected the rise of Japan as a major force in the international economy. Whereas Japan's own trade grew more widely oriented and the Western Pacific margins relatively less important as trading partners than before WW II, to the states of the Western Pacific Japan's status both as a supplier of imports and as an export market greatly enlarged —only rarely is Japan not the leading trading partner. The Japanese strategy of export-led growth has been replicated by South Korea, Taiwan, Hong Kong, and Singapore. All of these countries, as well as Japan itself, depend overwhelmingly on imports for their raw materials and energy supplies. Elsewhere trade patterns have been greatly modified by a rising spirit of nationalism that has emphasized development of manufacturing industries in Australia and New Zealand no less than in the states of SE Asia. 相似文献
15.
R. J. Fryer 《Geophysical Journal International》1975,42(3):893-898
Summary. The need for, and difficulties commonly experienced during, the analysis of patterns of vectors with superimposed 'noise' upon the surfaces of spheres is discussed. A simple procedure is described whereby many of these difficulties may be circumvented and certain classes of systematic array detected even against a considerable random background. An extension of the same procedure to the analysis of vector patterns in a plane is discussed. 相似文献
16.
B. Taylor G. Brown P. Fryer J.B. Gill A.G. Hochstaedter H. Hotta C.H. Langmuir M. Leinen A. Nishimura T. Urabe 《Earth and Planetary Science Letters》1990,100(1-3)
Bimodal volcanism, normal faulting, rapid sedimentation, and hydrothermal circulation characterize the rifting of the Izu-Bonin arc at 31°N. Analysis of the zigzag pattern, in plan view, of the normal faults that bound Sumisu Rift indicates that the extension direction (080° ± 10°) is orthogonal to the regional trend of the volcanic front. Normal faults divide the rift into an inner rift on the arc side, which is the locus for maximum subsidence and sedimentation, and an outer rift further west. Transfer zones that link opposing master faults and/or rift flank uplifts further subdivide the rift into three segments along strike. Volcanism is concentrated along the ENE-trending transfer zone which separates the northern and central rift segments. The differential motion across the zone is accommodated by interdigitating north-trending normal faults rather than by ENE-trending oblique-slip faults. Volcanism in the outer rift has built 50–700 m high edifices without summit craters whereas in the inner rift it has formed two multi-vent en echelon ridges (the largest is 600 m high and 16 km long). The volcanism is dominantly basaltic, with compositions reflecting mantle sources little influenced by arc components. An elongate rhyolite dome and low-temperature hydrothermal deposits occur at the en echelon step in the larger ridge, which is located at the intersection of the transfer zone with the inner rift. The chimneys, veins, and crusts are composed of silica, barite and iron oxide, and are of similar composition to the ferruginous chert that mantles the Kuroko deposits. A 1.2-km transect of seven alvin heat flow measurements at 30°48.5′N showed that the inner-rift-bounding faults may serve as water recharge zones, but that they are not necessarily areas of focussed hydrothermal outflow, which instead occurs through the thick basin sediments. The rift basin and arc margin sediments are probably dominated by permeable rhyolitic pumice and ash erupted from submarine arc calderas such as Sumisu and South Sumisu volcanoes. 相似文献
17.
Volcanism in the Sumisu Rift, I. Major element, volatile, and stable isotope geochemistry 总被引:2,自引:0,他引:2
Alfred G. Hochstaedter James B. Gill Minoru Kusakabe Sally Newman Malcolm Pringle Brian Taylor Patty Fryer 《Earth and Planetary Science Letters》1990,100(1-3)
A bimodal volcanic suite with KAr ages of 0.05–1.40 Ma was collected from the Sumisu Rift using alvin. These rocks are contemporaneous with island arc tholeiite lavas of the Izu-Ogasawara arc 20 km to the east, and provide a present day example of volcanism associated with arc rifting and back-arc basin initiation. Major element geochemistry of the basalts is most similar to that of basalts found in other, more mature back-arc basins, which indicates that back-arc basins need not begin their magmatic evolution with lavas bearing strong arc signatures.Volatile concentrations distinguish Sumisu Rift basalts from island arc basalts and MORB. H2O contents, which are at least four times greater than in MORB, suppress plagioclase crystallization. This suppression results in a more mafic fractionating assemblage, which prevents Al2O3 depletion and delays the initiation of Fe2O3(tot) and TiO2 enrichment. However, unlike arc basalts,Fe3+/ΣFe ratios are only slightly higher than in MORB and are insufficient to cause magnetite saturation early enough to suppress Fe2O3(tot) and TiO2 enrichment. Thus, major element trends are more similar to those of MORB than arcs.H2O, CO2 and S are undersaturated relative to pure phase solubility curves, indicating exsolution of an H2O-rich mixed gas phase. HighH2O/S, highδD, and low (MORB-like)δ34S ratios are considered primary and distinctive of the back-arc basin setting. 相似文献
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An approximately 20-m-thick alkali basalt flow on the Penghu Islands contains ∼20 cm thick, horizontally continuous (>50
m), vesicular layers separated by ∼1.5 m of massive basalt in its upper 8.5 m. The three layers contain ocelli-like "vesicles"
filled with nepheline and igneous carbonate. They are coarse grained and enriched in incompatible elements relative to the
massive basalt with which they form sharp contacts. These vesicular layers (segregation veins) formed when residual liquid
in the underlying crystal mush was forced (gas filter pressing) or siphoned into three thermally induced horizontal cracks
that opened successively in the advancing crystal mush of the flow's upper crust. Most vesicular layer trace elements can
be modelled by residual melt extraction after 25–40% fractional crystallization of massive basalt underlying each layer. Sulphur,
Cl, As, Zn, Pb, K, Na, Rb, and Sr show large concentration changes between the top, middle, and bottom layers, with each vesicular
and underlying massive basalt forming a chemically distinct "pair." The large changes between layers are difficult to account for by crystal fractionation alone, because other incompatible elements (e.g., La, Sm, Yb,
Zr, Nb) and the major elements change little. The association of these elements (S, Cl, etc.) with "fluids" in various geologic
environments suggests that volatiles influenced differentiation, perhaps by moving alkali, alkaline earth, and chalcophile
elements as magma-dissolved volatile complexes. Volatiles may have also led to large grain sizes in the segregation veins
by lowering melt viscosities and raising diffusion rates. The chemical variability between layers indicates that a convection
and concentration mechanism acted within the flow. The specific process cannot be determined, but different rates of vesicle
plume rise (through the flow) and/or accumulation in the upper crust's crystal mush might account for the chemical pairing
and extreme variations in Cl, S, As, and C. This study emphasizes the importance of sampling vesicular rocks in flows. It
also suggests that volatiles play important physical and chemical roles in rapidly differentiating mafic magmas in processes
decoupled from crystal fractionation.
Received: 11 November 1996 / Accepted: 20 September 1998 相似文献