Suprasubduction-zone peridotite in the northern USA Appalachians: evidence from mineral composition

2004 ◽  
Vol 68 (4) ◽  
pp. 699-708 ◽  
Author(s):  
R. A. Coish ◽  
P. Gardner
Keyword(s):  
Mineral Composition ◽  
Mineral Assemblage ◽  
Subduction Zones ◽  
Suprasubduction Zone ◽  
Collision Zone ◽  
Tectonic Environment ◽  
Depleted Mantle ◽  
Mineral Compositions ◽  
Early Palaeozoic ◽  
Very High

AbstractMineral compositions of small peridotite bodies in an Ordovician collision zone of the Vermont Appalachians provide important clues to their tectonic environment of origin. The bodies have been deformed and partially serpentinized under greenschist- to lower amphibolite-facies conditions during the Ordovician and Devonian. Before serpentinization, the peridotite bodies were dunite as shown by their mineral assemblage and by their high MgO, and low Ti and Al whole-rock contents. Despite deformation and metamorphism, remnant olivine and spinel grains occur; their compositions are taken to represent conditions prior to regional metamorphic events. High Mg/(Mg+Fe) in olivine and very high Cr/(Cr+Al) in spinel indicate that the peridotites formed as highly-depleted mantle residues. The compositions are similar to those in harzburgite and dunite from some ophiolites and from fore-arc regions of subduction zones. Accordingly, the southern Vermont peridotites probably formed in a forearc, supra-subduction zone during the Early Palaeozoic. They were subsequently emplaced by obduction of the upper plate of an east-facing subduction complex.

Study Of Structure Formation Of Organic-Mineral Compositions With Fibrous Filler By Electron Microscopy Method

2019 ◽  
pp. 41-47
Keyword(s):  
Electron Microscopy ◽  
Structure Formation ◽  
Mineral Composition ◽  
Bending Strength ◽  
Cement Stone ◽  
Hydrated Cement ◽  
Fibrous Filler ◽  
Organic Mineral ◽  
Microscopy Method ◽  
Mineral Compositions

The article presents the study of processes of structure formation of cement stone and products of hardening of organic-mineral compositions with fibrous filler (shavings) by the electronic scanning microscopy method. It is established that the additive-free cement stone at the age of 28 days has a dense and homogeneous structure, consists of calcium hydro-silicates, Portlandite and calcite - newgrowths characteristic for cement systems. Cellulose fibers, which make up the bulk of the substance of shavings, are sufficiently active, which determines the high adhesion of the hydration products of the cement binder to their surface. It is shown that the introduction of shavings into the organo-mineral composition leads to inhibition of cement hydration processes. Organo-mineral compositions with different shavings content (two compositions) were analyzed. The first composition is characterized by a fairly dense structure, the cement stone consists of globular nanoscale nuclei of hydrosilicates, Portlandite and calcite. The second composition has a loose porous structure, cement stone consists of non-hydrated cement grains, newgrowths are represented by calcite and vaterite. The structure of the contact zone "osprey fiber-cement stone" in the organo-mineral composition of the first composition indicates a good adhesion of the filler surface with the phases of hydrated cement. The use of shavings as a fibrous filler (the first composition) increases the tensile and bending strength, as well as the wear resistance of organo-mineral compositions. The data obtained by scanning electron microscopy are confirmed by the results of studying the processes of structure formation of cement stone by quantitative x-ray phase analysis.

Thorium in crandallite-group minerals: an example from a Devonian bauxite deposit, Timan, Russia

2004 ◽  
Vol 68 (3) ◽  
pp. 489-497 ◽  
Author(s):  
L. E. Mordberg
Keyword(s):  
Crystal Lattice ◽  
Radiation Damage ◽  
Mineral Composition ◽  
Bauxite Deposit ◽  
Weathering Profile ◽  
Silicate Mineral ◽  
Fe Content ◽  
Very High ◽  
Type Substitution ◽  
Simplified Formula

AbstractA Th-rich mineral of the crandallite group has been investigated from the weathering profile of the Schugorsk bauxite deposit, Timan, Russia. It occurs within thin (up to 0.5 mm) organic-rich veinlets together with ‘leucoxene’ in the form of small shapeless grains which vary in size from 1—2 mm to 60—70 mm. Rare grains disseminated among boehmite crystals were also found. Microprobe analyses determined that the ThO2 content can be as high as 18 wt.%. The mineral composition is intermediate between crandallite CaAl3H(PO4)2(OH)6, goyazite SrAl3H(PO4)2(OH)6, Th-crandallite and svanbergite SrAl3PO4SO4(OH)6 in the beudantite group.Comparatively high contents of Fe and Si and a very high positive Th and Fe content correlation (r = +0.98) suggest that the formula of the hypothetical Th-bearing end-member is ThFe3(PO4,SiO4)2(OH)6 with Th and Si substituting for REE and Prespectively (woodhouseite-type substitution). Another possible substitution is Th4+ + Ca2+ ⇋ 2REE3+ (florencite-type). A deficiency of cations in the X site can be explained by either the presence of carbon, undetectable by microprobe, in the crystal lattice or a lack of X-site cations due to radiation damage induced by Th. Some excess of cations in the B site (Al and Fe3+) can be explained by the presence of very small boehmite and hematite inclusions on the crandallite grain surfaces. Th-rich crandallite may be the result of alteration of an unidentified silicate mineral from the parent rock with a composition close to the simplified formula Fe2+ThSiO4(OH)2.

scholarly journals Up the down escalator: the exhumation of (ultra)-high pressure terranes during on-going subduction

2012 ◽  
Vol 4 (1) ◽  
pp. 745-781 ◽  
Author(s):  
C. J. Warren
Keyword(s):  
High Pressure ◽  
Subduction Zone ◽  
Continental Crust ◽  
Subduction Zones ◽  
Crustal Material ◽  
Time And Space ◽  
Ultra High Pressure ◽  
Tectonic Environment ◽  
Tectonic Style ◽  
Weak Material

Abstract. The exhumation of high and ultra-high pressure rocks is ubiquitous in Phanerozoic orogens created during continental collisions, and is common in many ocean-ocean and ocean-continent subduction zone environments. Three different tectonic environments have previously been reported, which exhume deeply buried material by different mechanisms and at different rates. However it is becoming increasingly clear that no single mechanism dominates in any particular tectonic environment, and the mechanism may change in time and space within the same subduction zone. In order for buoyant continental crust to subduct, it must remain attached to a stronger and denser substrate, but in order to exhume, it must detach (and therefore at least locally weaken) and be initially buoyant. Denser oceanic crust subducts more readily than more buoyant continental crust but exhumation must be assisted by entrainment within more buoyant and weak material such as serpentinite or driven by the exhumation of structurally lower continental crustal material. Weakening mechanisms responsible for the detachment of crust at depth include strain, hydration, melting, grain size reduction and the development of foliation. These may act locally or may act on the bulk of the subducted material. Metamorphic reactions, metastability and the composition of the subducted crust all affect buoyancy and overall strength. Subduction zones change in style both in time and space, and exhumation mechanisms change to reflect the tectonic style and overall force regime within the subduction zone. Exhumation events may be transient and occur only once in a particular subduction zone or orogen, or may be more continuous or occur multiple times.

Research on Process Mineralogy of Potassium-Rich Shale

2010 ◽  
Vol 158 ◽  
pp. 197-203 ◽  
Author(s):  
Jie Liu ◽  
Yue Xin Han ◽  
Wan Zhong Yin
Keyword(s):  
Chemical Composition ◽  
Mineral Composition ◽  
Potassium Feldspar ◽  
Composition Analysis ◽  
Research Results ◽  
Dsc Analyses ◽  
Process Mineralogy ◽  
Mineral Compositions ◽  
Chemical Composition Analysis

The process mineralogy of potassium-rich shale from Chaoyang of Liaoning, China, was studied. Research results showed there are much less variety and smaller quantities in mineral compositions. Calculated mineral composition by means of chemical composition analysis combined with XRD, MLA, IR and TG-DSC analyses showed that main minerals with were Potassium-feldspar, muscovite, biotite and illite, and gangue minerals were quartz and small amounts of hematite. Potassium-rich minerals such as potassium-feldspar and muscovite contact smoothly with quartz respectively, and there was the direction arrangement among potassium-feldspar, quartz and muscovite in the shale. And quartz and hematite were main cement in the shale. The influences of the research results on the potassium extraction from potassium-rich shale were distinct.

Effects of Compound Silicate Gangue on Mineral Composition and Microstructure of Sinter Produced by Baiyunebo Iron Ore Concentrates

2011 ◽  
Vol 194-196 ◽  
pp. 201-206
Author(s):  
Guo Ping Luo ◽  
Sheng Li Wu ◽  
Yi Ci Wang ◽  
Guang Jie Zhang ◽  
Zhi Zhong Hao ◽  
...  
Keyword(s):  
Mineral Composition ◽  
Iron Ore ◽  
Glassy Phase ◽  
Optical Microscope ◽  
Calcium Ferrite ◽  
Melting Time ◽  
Sintering Process ◽  
Test Device ◽  
Lower Melting Point ◽  
Mineral Compositions

The effects of compound silicate gangue on mineral composition and microstructure of sinter produced by Baiyunebo iron ore concentrates was studied by using mini-sintering test device and optical microscope. The result showed that compound silicate gangue has lower melting point, wider melting temperature range, longer melting time and melts easily to form glassiness during the sintering process. It can promote the solution of CaO and CaF2 in glassy phase, which affects viscosity and fluidity of glassy phase as well as the homogeneity of sinter microstructure. The compound silicate gangue intensely inhibits the generation of complex calcium ferrite and cuspidine as well. The major mineral compositions of sinter are hematite and glassy phase. The sinter exhibits multi-cavities and grainy structure when SiO2 exists entirely in the form of compound silicate gangue.

scholarly journals Adakites, High-Nb Basalts and Copper–Gold Deposits in Magmatic Arcs and Collisional Orogens: An Overview

Geosciences ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 29
Author(s):  
Pavel Kepezhinskas ◽  
Nikolai Berdnikov ◽  
Nikita Kepezhinskas ◽  
Natalia Konovalova
Keyword(s):  
Subduction Zones ◽  
Far East ◽  
Gold Deposits ◽  
Type I ◽  
Isotopic Signatures ◽  
Epithermal Mineralization ◽  
Depleted Mantle ◽  
Mantle Sources ◽  
East Russia ◽  
Collisional Orogens

Adakites are Y- and Yb-depleted, SiO2- and Sr-enriched rocks with elevated Sr/Y and La/Yb ratios originally thought to represent partial melts of subducted metabasalt, based on their association with the subduction of young (<25 Ma) and hot oceanic crust. Later, adakites were found in arc segments associated with oblique, slow and flat subduction, arc–transform intersections, collision zones and post-collisional extensional environments. New models of adakite petrogenesis include the melting of thickened and delaminated mafic lower crust, basalt underplating of the continental crust and high-pressure fractionation (amphibole ± garnet) of mantle-derived, hydrous mafic melts. In some cases, adakites are associated with Nb-enriched (10 ppm < Nb < 20 ppm) and high-Nb (Nb > 20 ppm) arc basalts in ancient and modern subduction zones (HNBs). Two types of HNBs are recognized on the basis of their geochemistry. Type I HNBs (Kamchatka, Honduras) share N-MORB-like isotopic and OIB-like trace element characteristics and most probably originate from adakite-contaminated mantle sources. Type II HNBs (Sulu arc, Jamaica) display high-field strength element enrichments in respect to island-arc basalts coupled with enriched, OIB-like isotopic signatures, suggesting derivation from asthenospheric mantle sources in arcs. Adakites and, to a lesser extent, HNBs are associated with Cu–Au porphyry and epithermal deposits in Cenozoic magmatic arcs (Kamchatka, Phlippines, Indonesia, Andean margin) and Paleozoic-Mesozoic (Central Asian and Tethyan) collisional orogens. This association is believed to be not just temporal and structural but also genetic due to the hydrous (common presence of amphibole and biotite), highly oxidized (>ΔFMQ > +2) and S-rich (anhydrite in modern Pinatubo and El Chichon adakite eruptions) nature of adakite magmas. Cretaceous adakites from the Stanovoy Suture Zone in Far East Russia contain Cu–Ag–Au and Cu–Zn–Mo–Ag alloys, native Au and Pt, cupriferous Ag in association witn barite and Ag-chloride. Stanovoy adakites also have systematically higher Au contents in comparison with volcanic arc magmas, suggesting that ore-forming hydrothermal fluids responsible for Cu–Au(Mo–Ag) porphyry and epithermal mineralization in upper crustal environments could have been exsolved from metal-saturated, H2O–S–Cl-rich adakite magmas. The interaction between depleted mantle peridotites and metal-rich adakites appears to be capable of producing (under a certain set of conditions) fertile sources for HNB melts connected with some epithermal Au (Porgera) and porphyry Cu–Au–Mo (Tibet, Iran) mineralized systems in modern and ancient subduction zones.

scholarly journals The Effect of Soil Mineral Composition on the Compressive Strength of Cement Stabilized Rammed Earth

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 324 ◽  
Author(s):  
Piotr Narloch ◽  
Piotr Woyciechowski ◽  
Jakub Kotowski ◽  
Ireneusz Gawriuczenkow ◽  
Emilia Wójcik
Keyword(s):  
Compressive Strength ◽  
Mineral Composition ◽  
Cement Content ◽  
Rammed Earth ◽  
Compression Tests ◽  
Soil Mineral ◽  
Sem Images ◽  
Mineral Compositions ◽  
Strength Result ◽  
Distribution Water

Cemented stabilized rammed earth (CSRE) is a building material used to build load bearing walls from locally available soil. The article analyzes the influence of soil mineral composition on CSRE compressive strength. Compression tests of CSRE samples of various mineral compositions, but the same particle size distribution, water content, and cement content were conducted. Based on the compression strength results and analyzed SEM images, it was observed that even small changes in the mineral composition significantly affected the CSRE compressive strength. From the comparison of CSRE compressive strength result sets, one can draw general qualitative conclusions that montmorillonite lowered the compressive strength the most; beidellite also lowered it, but to a lesser extent. Kaolinite lightly increased the compressive strength.

Geochemistry and eruptive environment of metavolcanic rocks from the Mona Complex of Anglesey, North Wales, U.K

1993 ◽  
Vol 130 (1) ◽  
pp. 85-91 ◽  
Author(s):  
R. S. Thorpe
Keyword(s):  
Volcanic Rocks ◽  
Fault Zones ◽  
Ultramafic Rocks ◽  
Chemical Analyses ◽  
Late Precambrian ◽  
Suprasubduction Zone ◽  
Metavolcanic Rocks ◽  
North Wales ◽  
Eruptive Environment ◽  
Early Palaeozoic

AbstractThe late Precambrian–early Palaeozoic Monian Supergroup of the Mona Complex is a thick sequence of flysch-type sediments and metavolcanic rocks which were deposited during the late Precambrian–early Palaeozoic and deformed during the late Precambrian and Caledonian (Ordovician/Silurian) orogenies. The Monian Supergroup includes tectonically emplaced, geographically separated outcrops of metabasalt/andesite, gabbro and serpentinized ultramafic rocks all of ophiolite affinity. The major units of the Mona Complex are separated by important faults/fault zones which may represent terrane boundaries. New chemical analyses, together with existing ones, show that the metabasalts and meta-andesites from the older New Harbour Group of north Anglesey have characteristics of suprasubduction zone arc eruptives whereas the metabasalts from the younger Gwna Group of south Anglesey and Lleyn have MORB geochemistry. It is suggested that these volcanic rocks were produced during the late Precambrian–early Palaeozoic development of the lapetus Ocean and emplaced as separate terranes during its closure.

Proximate and Mineral Compositions, Mineral Safety Index (MSI) of Ten Organs of African Giant Pouch Rat

2018 ◽  
Vol 9 ◽  
pp. 1-9 ◽  
Author(s):  
Emmanuel Ilesanmi Adeyeye ◽  
Adeolu Jonathan Adesina
Keyword(s):  
Mineral Composition ◽  
Proximate Composition ◽  
Heart Muscle ◽  
Crude Protein ◽  
Metabolizable Energy ◽  
Safety Index ◽  
Energy Contribution ◽  
Nutritional Information ◽  
Standard Methods ◽  
Mineral Compositions

An investigation into the proximate composition, mineral composition and the mineral safety index of heart, skin, muscle, lungs, tongue, kidney, spleen, brain, liver and eyes of African giant pouch rat was carried out using standard methods, calculations of metabolizable energy, percentage energy contribution due to: protein, fat and carbohydrate; utilizable energy due to protein; Ca/P, Na/K, [K/(Ca+Mg)], Ca/Mg ratios and mineral safety index. In the proximate composition, the followings were discovered: samples were good in muscle (ash), kidney (protein), muscle (crude fat), skin (carbohydrate) and also contributed the highest energy. Highest level of proportion of energy due to protein (PEP %) came from the kidney, highest level of energy due to fat (PEF %) came from muscle whilst highest energy contribution due to carbohydrate (PEC %) came from the skin. The utilizable energy due to protein (UEDP %) assuming 60% utilisation had the highest level in the kidney. In the mineral composition muscle was good in Na; muscle was best in K; kidney was highest in Ca; tongue was rich in Mg; spleen was high in zinc; liver was high in Fe; muscle was rich in Mn; kidney was rich in P; muscle was good in Ca/P; skin was best in Na/K; spleen was best in [K/(Ca+Mg)] and spleen was best in Ca/Mg. In the mineral safety index (MSI) values: Zn with MSI of 33 was lower than heart, spleen and in Fe with MSI of 6.7 was lower than heart, muscle, lungs, brain, liver and eyes. The following parameters were significantly different at α = 0.05 among the samples: crude protein, carbohydrate, PEP %, PEF %, PEC %, UEDP %, Na, K, Ca, Mg, Zn, Fe and P. This report will give nutritional information on the various organs analysed.

Geodynamic evolution of the southern Abitibi and Pontiac terranes: evidence from geochemistry of granitoid magma series (2700–2630 Ma)

1992 ◽  
Vol 29 (10) ◽  
pp. 2266-2286 ◽  
Author(s):  
Rui Feng ◽  
Rob Kerrich
Keyword(s):  
Rare Earth ◽  
Partial Melting ◽  
Alkali Feldspar ◽  
Quartz Syenite ◽  
Southern Volcanic Zone ◽  
Suprasubduction Zone ◽  
Depleted Mantle ◽  
Quartz Monzonite ◽  
Ree Patterns ◽  
Low K

Four distinct granitic series developed during the evolution of the Archean Abitibi Southern Volcanic Zone (SVZ): (1) A minor synvolcanic tonalite–trondhjemite–granodiorite (TTG) series was emplaced at ~2700 Ma, which has extremely low K2O (<1.5 wt.%), Rb (<50 ppm), and Sr (<200 ppm), higher Nb, Y, and Sc, flat rare-earth-element (REE) patterns, and negative Eu anomalies. (2) A voluminous tonalite – granodiorite – granite – quartz monzonite (TGGM) series developed syntectonically at ~2695–2685 Ma, and displays low K2O (1–3 wt.%), Rb (10–50 ppm), Ba (<1000 ppm), and U, enhanced Sr, depletion of Ta, Nb, and Ti, and strongly fractionated REE patterns (La/Ybn = 49–21). (3) A late-tectonic quartz syenite – quartz monzonite – granite (SMG) series was emplaced from ~2685 to 2675 Ma, and is grossly similar to the TGGM but has lower CaO/(K2O + Na2O) and greater concentrations of Rb, Ba, Th, and U. (4) A late-tectonic to posttectonic alkali feldspar syenite – alkali feldspar quartz syenite (SS) series was emplaced from 2680 to 2670 Ma, and occurs along regional strike-slip structures. The primitive rocks (SiO2 ≤ 65 wt.%) exhibit coenrichment of large-ion lithophile elements (LILE) and mafic elements (Cr, Co, and Ni) and strongly fractionated REE patterns, whereas evolved phases (SiO2 ≥ 65 wt.%) display lower contents of compatible and incompatible elements stemming from differentiation.In the adjacent Pontiac Subprovince and the Lacorne block within the SVZ, two granitic series predominate: (1) A syntectonic to late-tectonic monzodiorite–monzonite–granodiorite–syenite (MMGS) series (2690–2670 Ma) is comparable to the Abitibi SMG and SS series in most major-element, LILE, and REE contents but is distinguished by high MgO contents, extremely high Ba/Th ratios, and coenrichment of Cr, Co, and Ni with light rare-earth elements (LREE), Li, and Cs. (2) A garnet–muscovite–granite (GMG) series (2644 ± 13 Ma) displays K2O/Na2O ≥ 1, restricted SiO2 range (69–75 wt.%), pronounced enrichments of Rb, Li, Cs, Ta, Nb, Th, and U, and moderately fractionated REE's (La/Ybn = 16–0.9), with prominent negative Eu anomalies.The synvolcanic TTG series is interpreted to have formed by differentiation of low-K mafic magmas of the Blake River Group type in suprasubduction-zone environments. Geochemical compositions of the TGGM, SGM, SS, and MMGS series resemble those of Phanerozoic granitoids in island-arc settings and reflect a transition from partial melting of the subducted or subcreted slab to melting of the metasomatized depleted mantle wedge assisted by LILE- and LREE-enriched fluids released from the slab. The GMG, which formed by partial melting of the Pontiac metasediments when the Pontiac Sub-province collided with and underthrust the Abitibi SVZ at ~2670 Ma, is similar to Himalayan collisional leucogranites.

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