Layered rhyolite bands in a thick North Mountain Basalt flow: the products of silicate liquid immiscibility?

1992 ◽  
Vol 56 (384) ◽  
pp. 309-318 ◽  
Author(s):  
John D. Greenough ◽  
J. Dostal
Keyword(s):  
Liquid Immiscibility ◽  
Immiscible Liquid ◽  
Chemical Compositions ◽  
Forming Process ◽  
Basalt Flow ◽  
Immiscible Liquids ◽  
Fine Grained ◽  
Mafic Intrusions ◽  
Bulk Chemical ◽  
Rich Liquid

AbstractThe upper 35 m of a thick (≤175 m) Early Jurassic North Mountain Basalt flow at KcKay Head contains 25 cm thick differentiated layers that are separated by 130 cm sections of basalt. The lower layers are mafic, pegmatitic, and contain thin (2 cm), fine-grained 'rhyolite' bands. Evidence that the rhyolite represents a Si-rich immiscible liquid includes: (1) textures such as fiine-grained globules of Ferich pyroxene (once Fe-rich liquid) bordering pegmatite feldspar grains; (2) structureless, microcrystalline, interstitial, polygonal patches of Si-rich minerals and similar areas of Fe-rich stilpnomelane surrounding skeletal Fe-Ti oxide grains, with bulk chemical compositions (to a first approximation), relative proportions and total modat percentages suggesting they were once Si-rich and Fe-rich glasses respectively; (3) basalt and pegmatite compositions (particularly their Fe, and Ti contents) similar to rocks known to contain immiscible liquids; (4) rhyolite major element compositions generally consistent with formation from an immiscible Si-rich liquid; (5) mineral compositions and temperature of pegmatite formation compatible with immiscibility; (6) the inability of mass balance calculations (crystal fractionation) to explain rhyolite formation unless mesostasis stilpnomelane (representing the Fe-rich liquid) is included in the caculations. If, as we suggest, these rocks are the result of immiscibility, they shed light on the incipient formation of granophyres in mafic intrusions and support liquid immiscibility as an important rock-forming process.

Archean Boninite-like Rocks of the Northwestern Youanmi Terrane, Yilgarn Craton: Geochemistry and Genesis

2019 ◽  
Vol 60 (11) ◽  
pp. 2131-2168 ◽  
Author(s):  
Jack R Lowrey ◽  
Derek A Wyman ◽  
Tim J Ivanic ◽  
R Hugh Smithies ◽  
Roland Maas
Keyword(s):  
Trace Element ◽  
Crustal Contamination ◽  
Mantle Metasomatism ◽  
Chemical Compositions ◽  
Yilgarn Craton ◽  
Fine Grained ◽  
Mafic Intrusions ◽  
Field Evidence ◽  
Isotopic Analyses ◽  
Geochemical Analyses

Abstract Rocks with chemical compositions similar to Cenozoic boninites occur in many Archean cratons (boninite-like rocks), but they are rarely well-preserved, well-sampled, or presented within chrono- and chemo-stratigraphic context. This study provides a detailed description of the most extensive and well-preserved Archean boninite-like rocks reported to date. Within the 2820 to 2740 Ma magmatic suites of the northwest Youanmi Terrane, Yilgarn Craton, boninite-like rocks occur as two distinct units. The first boninite-like unit is thinner (several 10 s of m thick), occurs close to the base of the 2820–2800 Ma Norie Group and includes both volcanic flows and subvolcanic intrusions. The second boninite-like unit is thicker (locally several 100 s m), occurs near the base of the 2800–2740 Ma Polelle Group and consists of mainly fine-grained volcanic flows with local cumulate units. On average, major and trace element compositions for Youanmi Terrane boninite-like rocks are marginal between basalt, picrite and boninite and they have asymmetrically concave REE patterns, and Th–, Zr–Hf enrichments, similar to many Phanerozoic low-Si boninite suites, but at generally higher MREE–HREE contents. We report over 300 new whole-rock geochemical analyses, and 16 new Sm–Nd isotopic analyses, and associated petrographic evidence, including representative mineral compositions, which we support with published geochemical analyses and several decades of fieldwork in our study area. Comparison between Archean boninite-like rocks and Cenozoic boninites shows that most Archean examples had less depleted sources. We consider two possible petrogenetic models for the Youanmi Terrain examples: (1) they reflect variably contaminated komatiites, or (2) they reflect melts of metasomatised refractory mantle, analogous to Phanerozoic boninites. Trace element modelling indicates that crustal contamination could potentially produce rocks with boninite-like compositions, but requires an Al-enriched komatiitic parent liquid, for which there is no field evidence in our study area. Initial εNdT values in pre-2800 Ma rocks (εNdT -0·4 to +1·2) are on average slightly higher than those in 2800–2733 Ma examples (εNdT -3·2 to +1·2), compatible with increasing mantle metasomatism involving recycling of ≥ 2950 Ma crust. Integration of trace element and Nd isotopic data demonstrates that significant direct crustal assimilation was restricted to felsic magmas. The Th–Nb and Ba–Th systematics of mafic-intermediate rocks reflect fluid- and sediment-derived processes in the mantle, with boninite-like examples being linked primarily to fluid metasomatism. We compare the well-preserved igneous textures and mineralogy of Youanmi Terrane boninite-like rocks with those of their Phanerozoic counterparts, and based on studies of the latter, suggest that former had similarly hot, H2O-rich parent magmas. The association of boninite-like rocks in the Norie and Polelle Groups with coeval high-Mg andesites, sanukitoids and hydrous mafic intrusions of the Narndee Igneous Complex strongly suggests a metasomatised mantle source and subduction operating in the Yilgarn between 2820 and 2730 Ma.

scholarly journals Immiscible silicate liquids: K and Fe distribution as a test for chemical equilibrium and insight into the kinetics of magma unmixing

2021 ◽  
Vol 176 (6) ◽  
Author(s):  
Alexander Borisov ◽  
Ilya V. Veksler
Keyword(s):  
Regression Analysis ◽  
Chemical Equilibrium ◽  
Volcanic Rocks ◽  
Experimental Studies ◽  
Liquid Immiscibility ◽  
Immiscible Liquid ◽  
Liquid Droplets ◽  
Liquid Distribution ◽  
Immiscible Liquids ◽  
Element Partitioning

AbstractSilicate liquid immiscibility leading to formation of mixtures of distinct iron-rich and silica-rich liquids is common in basaltic and andesitic magmas at advanced stages of magma evolution. Experimental modeling of the immiscibility has been hampered by kinetic problems and attainment of chemical equilibrium between immiscible liquids in some experimental studies has been questioned. On the basis of symmetric regular solutions model and regression analysis of experimental data on compositions of immiscible liquid pairs, we show that liquid–liquid distribution of network-modifying elements K and Fe is linked to the distribution of network-forming oxides SiO2, Al2O3 and P2O5 by equation: $$\log K_{{\text{d}}}^{{\text{K/Fe}}} = \, 3.796\Delta X_{{{\text{SiO}}_{2} }}^{{{\text{sf}}}} + \, 4.85\Delta X_{{{\text{Al}}_{2} {\text{O}}_{3} }}^{{{\text{sf}}}} + \, 7.235\Delta X_{{{\text{P}}_{2} {\text{O}}_{5} }}^{{{\text{sf}}}} - \, 0.108,$$ log K d K/Fe = 3.796 Δ X SiO 2 sf + 4.85 Δ X Al 2 O 3 sf + 7.235 Δ X P 2 O 5 sf - 0.108 , where $$K_{{\text{d}}}^{{\text{K/Fe}}}$$ K d K/Fe is a ratio of K and Fe mole fractions in the silica-rich (s) and Fe-rich (f) immiscible liquids: $$K_{d}^{{\text{K/Fe}}} = \, \left( {X_{{\text{K}}}^{s} /X_{{\text{K}}}^{f} } \right)/ \, \left( {X_{{{\text{Fe}}}}^{s} /X_{{{\text{Fe}}}}^{f} } \right)$$ K d K/Fe = X K s / X K f / X Fe s / X Fe f and $$\Delta X_{{\text{i}}}^{sf}$$ Δ X i sf is a difference in mole fractions of a network-forming oxide i between the liquids (s) and (f): $$\Delta X_{i}^{sf} = X_{i}^{s} - X_{i}^{f}$$ Δ X i sf = X i s - X i f . We use the equation for testing chemical equilibrium in experiments not included in the regression analysis and compositions of natural immiscible melts found as glasses in volcanic rocks. Departures from equilibrium that the test revealed in crystal-rich multiphase experimental products and in natural volcanic rocks imply kinetic competition between liquid–liquid and crystal–liquid element partitioning. Immiscible liquid droplets in volcanic rocks appear to evolve along a metastable trend due to rapid crystallization. Immiscible liquids may be closer to chemical equilibrium in large intrusions where cooling rates are lower and crystals may be spatially separated from liquids.

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

scholarly journals Preliminary Characterization of Three Metallurgical Bauxite Residue Samples

2021 ◽  
Vol 5 (1) ◽  
pp. 66
Author(s):  
Panagiotis Angelopoulos ◽  
Maria Georgiou ◽  
Paschalis Oustadakis ◽  
Maria Taxiarchou ◽  
Hakan Karadağ ◽  
...  
Keyword(s):  
Low Cost ◽  
Bauxite Residue ◽  
Raw Material ◽  
Morphological Observation ◽  
Critical Metals ◽  
Alumina Production ◽  
Preliminary Characterization ◽  
Fine Grained ◽  
Extraction And Separation ◽  
Bulk Chemical

Bauxite Metallurgical Residue (BR) is a highly alkaline and very fine-grained by-product of the Bayer process for alumina production. Its huge global annual production has resulted in increasing accumulation of BR, causing deposition problems and serious environmental issues. RM contains oxides and salts of the main elements Fe, Al, Ca, Na, Si, Ti, and rare earths—REEs (Sc, Nd, Y, La, Ce, Ds)—many of which have been categorised by EU as critical metals (CMs). The valorisation of BR as a low-cost secondary raw material and metal resource could be a route for its reduction, introducing the waste into the economic cycle. REEScue constitutes a research project that aims to instigate the efficient exploitation of European bauxite residues, resulting from alumina production from Greece (MYTILINEOS SA), Turkey (ETI Aluminium), and Romania (ALUM SA), containing appreciable concentrations of scandium and REEs, through the development of a number of innovative extraction and separation technologies that can efficiently address the drawbacks of the existing solution. The consortium consists of three alumina producers from Greece (MYTILINEOS SA), Turkey (ETI Aluminium), and Romania (ALUM SA) and two academic partners from Greece (National Technical University of Athens) and Turkey (Necmettin Erbacan University). We present preliminary characterization results of three different BR samples that originate from the three aluminium industries, in respect of bulk chemical analysis (XRF, ICP), mineralogical investigation (XRD), and morphological observation through microscopy.

scholarly journals Synrift sandstones and clayey rocks: bulk chemical composition and location on a number of discriminant paleogeodynamic diagrams

2019 ◽  
pp. 439-465
Author(s):  
A. V. Maslov ◽  
V. N. Podkovyrov ◽  
E. Z. Gareev ◽  
A. D. Nozhkin
Keyword(s):  
Chemical Composition ◽  
Continental Margins ◽  
Bulk Chemical Composition ◽  
East European ◽  
Fine Grained ◽  
Sedimentary Deposits ◽  
Data Points ◽  
Bulk Chemical ◽  
Clayey Rocks ◽  
Active Continental Margins

The bulk chemical composition of synrift sandstones and associated clayey rocks has been analized, and the distribution of the fields they form has been studied on discriminant paleogeodynamic SiO2K2O/Na2O [Roser, Korsch, 1986] and DF1DF2 [Verma, Armstrong-Altrin, 2013] diagrams. The studied sandstones in terms of bulk chemical composition mainly correspond to greywacke, lititic, arkose and subarkose psammites; Sublitites and quartz arenites are also found. A significant part in the analyzed data massif consists of psammites, in which log(Na2O/K2O)-1.0; missing on the Pettijohn classification chart. This confirms our conclusion, based on the results of mineralogical and petrographic studies, that the sedimentary infill of rift structures unites immature sandstones, the detrital framework of which was formed due to erosion of local sources, represented by various magmatic and sedimentary formations. Synrift clayey rocks, compared with sandstones, are composed of more mature fine-grained siliciclastics. As follows from the distribution of figurative data points of clayey rocks on the F1F2 diagram [Roser, Korsch, 1988], its sources were mainly sedimentary deposits. The content of most of the main rock-forming oxides in the synrift sandstones is almost the same as in silt-sandstone rocks present in the Upper Precambrian-Phanerozoic sedimentary mega-complex of the East European Plate, but at the same time differs significantly from the Proterozoic and Phanerozoic cratonic sediments, as well as from the average composition upper continental crust. It is shown that the distribution of the fields of syntift sandstones and clayey rocks on the SiO2K2O/Na2O diagram does not have any distinct features, and their figurative data points are localized in the areas of terrigenous rocks of passive and active continental margins. On the DF1DF2 diagram, the fields of the studied psammites and clayey rocks are located in areas of riftogenous and collisional environments. We have proposed a different position of the border between these areas in the diagram, which will require further verification.

scholarly journals Compositional boundary layers trigger liquid unmixing in a basaltic crystal mush

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Victoria C. Honour ◽  
Marian B. Holness ◽  
Bernard Charlier ◽  
Sandra C. Piazolo ◽  
Olivier Namur ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Liquid Immiscibility ◽  
Atom Probe ◽  
Immiscible Liquid ◽  
Ore Deposits ◽  
Crystal Mush ◽  
Compositional Zoning ◽  
Resolution Imaging ◽  
River Plain ◽  
Crystal Interfaces

Abstract The separation of immiscible liquids has significant implications for magma evolution and the formation of magmatic ore deposits. We combine high-resolution imaging and electron probe microanalysis with the first use of atom probe tomography on tholeiitic basaltic glass from Hawaii, the Snake River Plain, and Iceland, to investigate the onset of unmixing of basaltic liquids into Fe-rich and Si-rich conjugates. We examine the relationships between unmixing and crystal growth, and the evolution of a nanoemulsion in a crystal mush. We identify the previously unrecognised role played by compositional boundary layers in promoting unmixing around growing crystals at melt-crystal interfaces. Our findings have important implications for the formation of immiscible liquid in a crystal mush, the interpretations of compositional zoning in crystals, and the role of liquid immiscibility in controlling magma physical properties.

scholarly journals Mineralogy of Silicate-Natrophosphate Immiscible Inclusion in Elga IIE Iron Meteorite

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 437
Author(s):  
Victor V. Sharygin
Keyword(s):  
Microprobe Analysis ◽  
Electron Microprobe Analysis ◽  
Liquid Immiscibility ◽  
Iron Meteorite ◽  
New Mineral ◽  
Rare Type ◽  
Fine Grained ◽  
New Mineral Species ◽  
Silicate Inclusions ◽  
Dominant Phase

Rare type of silicate inclusions found in the Elga iron meteorite (group IIE) has a very specific mineral composition and shows silicate (≈90%)–natrophosphate (≈10%) liquid immiscibility due to meniscus-like isolation of Na-Ca-Mg-Fe phosphates. The 3 mm wide immiscible inclusion has been first studied in detail using optical microscopy, scanning electron microscopy, electron microprobe analysis and Raman spectroscopy. The silicate part of the inclusion contains fine-grained quartz-feldspar aggregate and mafic minerals. The relationships of feldspars indicate solid decay of initially homogenous K-Na-feldspar into albite and K-feldspar with decreasing of temperature. Some mafic minerals in the silicate part are exotic in composition: the dominant phase is an obertiite-subgroup oxyamphibole (amphibole supergroup), varying from ferri-obertiite NaNa2Mg3Fe3+Ti[Si8O22]O2 to hypothetical NaNa2Mg3Fe2+0.5Ti1.5[Si8O22]O2; minor phases are the aenigmatite-subgroup mineral (sapphirine supergroup) with composition close to median value of the Na2Fe2+5TiSi6O18O2-Na2Mg5TiSi6O18O2 join, orthopyroxene (enstatite), clinopyroxene of the diopside Ca(Mg,Fe)Si2O6–kosmochlor NaCrSi2O6-Na(Mg,Fe)0.5Ti0.5Si2O6 series and chromite. The alteration phases are represented by Fe-dominant chlorite, goethite and hydrated Na2O-rich (2.3–3.3 wt.%) Fe-phosphate close to vivianite. Natrophosphate part consists of aggregate of three orthophosphates (brianite, czochralskiite, marićite) and minor Na-Cr-Ti-clinopyroxene, pentlandite, rarely taenite. Czochralskiite Na4Ca3Mg(PO4)4 is rich in FeO (2.3–5.1 wt.%) and MnO (0.4–1.5 wt.%). Brianite Na2CaMg(PO4)2 contains FeO (3.0–4.3 wt.%) and MnO (0.3–0.7 wt.%) and marićite NaFe(PO4) bears MnO (5.5–6.2 wt.%), MgO (5.3–6.2 wt.%) and CaO (0.5–1.5 wt.%). The contact between immiscible parts is decorated by enstatite zone in the silicate part and diopside–kosmochlor clinopyroxene zone in the natrophosphate ones. The mineralogy of the studied immiscible inclusion outlines three potentially new mineral species, which were first identified in meteorites: obertiite–related oxyamphibole NaNa2Mg3Fe2+0.5Ti1.5[Si8O22]O2, Mg-analog of aenigmatite Na2Mg5TiSi6O18O2 and Na-Ti-rich clinopyroxene Na(Mg,Fe)0.5Ti0.5Si2O6.

Melting in the Fe-FeO system to 204 GPa: Implications for oxygen in Earth's core

2019 ◽  
Vol 104 (11) ◽  
pp. 1603-1607 ◽  
Author(s):  
Kenta Oka ◽  
Kei Hirose ◽  
Shoh Tagawa ◽  
Yuto Kidokoro ◽  
Yoichi Nakajima ◽  
...  
Keyword(s):  
Inner Core ◽  
Liquid Core ◽  
Light Element ◽  
Liquid Immiscibility ◽  
Eutectic Liquid ◽  
Core Boundary ◽  
Diamond Anvil ◽  
Rich Liquid ◽  
Melting Experiments ◽  
Carbon Concentrations

Abstract We performed melting experiments on Fe-O alloys up to 204 GPa and 3500 K in a diamond-anvil cell (DAC) and determined the liquidus phase relations in the Fe-FeO system based on textural and chemical characterizations of recovered samples. Liquid-liquid immiscibility was observed up to 29 GPa. Oxygen concentration in eutectic liquid increased from >8 wt% O at 44 GPa to 13 wt% at 204 GPa and is extrapolated to be about 15 wt% at the inner core boundary (ICB) conditions. These results support O-rich liquid core, although oxygen cannot be a single core light element. We estimated the range of possible liquid core compositions in Fe-O-Si-C-S and found that the upper bounds for silicon and carbon concentrations are constrained by the crystallization of dense inner core at the ICB.

Microstructures, Tensile Properties and Forming Process of AZ31 Alloy Sheets

2007 ◽  
Vol 546-549 ◽  
pp. 241-244 ◽  
Author(s):  
Yun Qi Yan ◽  
H. Zhang ◽  
Q. Chen ◽  
H. Zhong ◽  
W.P. Weng
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Tensile Properties ◽  
Cell Phone ◽  
Az31 Alloy ◽  
Forming Process ◽  
Fine Grained ◽  
Forming Temperature ◽  
Scanning Electron

Rolling and punching techniques of AZ31 alloy were investigated in this paper. Various rolling experiments were carried out to make fine-grained Mg sheets. Punching tests were conducted at the temperatures range from 70 to 300 oC. The analysis revealed that there existed an excellent warm forming temperature for as-rolled AZ31 alloy. A warm deep punching tool setup using heating elements was designed and manufactured to produce the cell phone. Microstructures were observed using optical and scanning electron microscope equipped with EBSD. The textures in as-rolled and as-annealed specimens attribute to different mechanical properties along the various direction.

A REVIEW OF THE HYDROCARBON HABITAT OF THE EASTERN AND CENTRAL BARROW — DAMPIER SUB-BASIN, WESTERN AUSTRALIA

1985 ◽  
Vol 25 (1) ◽  
pp. 154 ◽  
Author(s):  
E. Kopsen ◽  
G. McGann
Keyword(s):  
Coarse Grained ◽  
Hydrocarbon Source Rock ◽  
Mixed Composition ◽  
Fine Grained ◽  
Third Phase ◽  
Dynamic Charging ◽  
Rich Liquid ◽  
Northern Carnarvon Basin ◽  
And Migration ◽  
Carnarvon Basin

The most completely known section of the Barrow- Dampier Sub-basin in the northern Carnarvon Basin of the Northwest Shelf comprises three depositional super- cycles spanning the Triassic to the Tertiary. Each cycle is made up of an initial transgressive section of mainly fine-grained clastics overlain by a thick, extensive, off- lapping sequence of coarse-grained deposits. The transgressive sedimentary package typically contains a coarse basal unit overlain by a thick, argillaceous unit, whereas the progradational package changes character in each cycle, representing increasingly open marine conditions as the depocentre and its palaeogeography evolved. Continental siliciciastics at the end of the Triassic Supercycle contrast with the marine-marginal marine siliciciastics at the end of the Jurassic-Neocomian Supercycle and the prograding Tertiary carbonate wedge of the youngest cycle. Each of these gross sequences has a distinctive seismic signature upon which are superimposed stratigraphic features reflecting basin evolution from a broad intra-continental depocentre to a mature, passive continental margin basin.In the area east of Barrow Island, potential hydrocarbon source rock quality and richness varies between each cycle but potential source beds frequently occur at similar levels within each supercycle. The Dingo Claystone within the Jurassic-Neocomian depositional package contains by far the thickest and most extensive potential sources in the area and is likely to be the source for most of the hydrocarbon liquids discovered to date in the northern Carnarvon Basin (with the probable exclusion of the majority of the Rankin Platform condensates).The occurrence of oils of mixed composition and considerable variability beneath the Muderong Shale regional seal in areas of low thermal maturity suggests that many of the hydrocarbon liquids have undergone considerable vertical migration and have also a complex genesis. Furthermore, saturate-rich liquid hydrocarbons overprinting an older biodegraded oil are recognised in a number of wells along the basin margin hingeline. The likely migration and entrapment model for the majority of hydrocarbons discovered to date in the area under review involves dynamic charging of reservoirs, mainly during the Tertiary. Two main pulses of generation and migration are recognised in the eastern portion of the sub -basin, and a third phase is probably occuring at present-day, west of Barrow Island.

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