Kyanite-bearing eclogite xenoliths from the Udachnaya kimberlite, Siberian craton, Russia

2017 ◽  
Vol 188 (1-2) ◽  
pp. 7 ◽  
Author(s):  
Ioana-Bogdana Radu ◽  
Bertrand Moine ◽  
Dmitri Ionov ◽  
Andrey Korsakov ◽  
Alexander Golovin ◽  
...  
Keyword(s):  
Siberian Craton ◽  
Major Element ◽  
Kimberlite Pipe ◽  
West African ◽  
Coarse Grained ◽  
Chemical Compositions ◽  
Type I ◽  
Type Ii ◽  
Major Element Composition ◽  
Subducted Oceanic Crust

Xenoliths brought up by kimberlite magmas are rare samples of otherwise inaccessible lithospheric mantle. Eclogite xenoliths are found in most cratons and commonly show a range of mineral and chemical compositions that can be used to better understand craton formation. This study focuses on five new kyanite-bearing eclogites from the Udachnaya kimberlite pipe (367±5 Ma). They are fine-to coarse-grained and consist mainly of “cloudy” clinopyroxene (cpx) and garnet (grt). The clinopyroxene is Al,Na-rich omphacite while the garnet is Ca-rich, by contrast to typical bi-mineral (cpx+grt) eclogites that contain Fe- and Mg-rich garnets. The Udachnaya kyanite eclogites are similar in modal and major element composition to those from other cratons (Dharwar, Kaapvaal, Slave, West African). The kyanite eclogites have lower REE concentrations than bi-mineral eclogites and typically contain omphacites with positive Eu and Sr anomalies, i.e. a “ghost plagioclase signature”. Because such a signature can only be preserved in nonmetasomatised samples, we infer that they were present in the protoliths of the eclogites. It follows that subducted oceanic crust is present at the base of the Siberian craton. Similar compositions and textures are also seen in kyanite eclogites from other cratons, which we view as evidence for an Archean, subduction-like formation mechanism related to craton accretion. Thus, contrary to previous work that classifies all kyanite eclogites as type I (IK), metasomatized by carbonatite/kimberlitic fluids, we argue that some of them, both from this work and those from other cratons, belong to the non-metasomatized type II (IIB). The pristine type IIB is the nearest in composition to protoliths of mantle eclogites because it contains no metasomatic enrichments.

Episodic tourmaline growth and re-equilibration in mica pegmatite from the Bihar Mica Belt, India: major- and trace-element variations under pegmatitic and hydrothermal conditions

2016 ◽  
Vol 154 (1) ◽  
pp. 68-86 ◽  
Author(s):  
PRANJIT HAZARIKA ◽  
DEWASHISH UPADHYAY ◽  
KAMAL LOCHAN PRUSETH
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Major Element ◽  
Element Composition ◽  
Coarse Grained ◽  
Partial Replacement ◽  
Type I ◽  
Type Ii ◽  
Hydrothermal Conditions ◽  
Major Element Composition

AbstractMica pegmatites from the Bihar Mica Belt contain three distinct generations of tourmaline. The major-element composition, substitution vectors and trajectories within each group are different, which indicates that the three types of tourmalines are not a part of one evolutionary series. Rather, the differences in their chemistries as well their mutual microtextural relations, can be best explained by growth of tourmaline from pegmatitic melts followed by episodic re-equilibration during discrete geological events. The euhedral, coarse-grained brown type I tourmaline cores have relatively high Ca, Mg (XMgc. 0.37) and Al with correlated variation in Sr, Sc, Ti, Zr, Y, Cr, Pb and Rare Earth elements (REEs). They are inferred to have crystallized from pegmatitic melts. Monazites included within these tourmalines give chemical ages of 1290−1242 Ma interpreted to date the crystallization of the pegmatitic tourmaline. The bluish type II and greyish type III tourmalines with low Ca and Mg contents (XMg = 0.16−0.27) and high Zn, Sn, Nb, Ta and Na, formed by pseudomorphic partial replacement of the pegmatitic tourmaline via fluid-mediated coupled dissolution–reprecipitation, are ascribed to a hydrothermal origin. The ages obtained from monazites included in these tourmalines indicate two alteration events at c. 1100 Ma and c. 950 Ma. The correlated variation of Ca, Mg and Fe and the trace elements Sr, Sn, Sc, Zn and REE within the tourmalines indicates that the trace-element concentrations of tourmaline are controlled not only by the fluid chemistry but also by coupled substitutions with major-element ions.

scholarly journals Composition and origin of nodules from the ≈20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma — Vesuvius, Italy

2012 ◽  
Vol 4 (2) ◽  
Author(s):  
Rita Klébesz ◽  
Robert Bodnar ◽  
Benedetto Vivo ◽  
Kálmán Török ◽  
Annamaria Lima ◽  
...  
Keyword(s):  
Melt Inclusions ◽  
Alkali Feldspar ◽  
Sem Analysis ◽  
Chemical Compositions ◽  
Type I ◽  
Type Ii ◽  
Vapor Bubbles ◽  
Ti Oxides ◽  
Basaltic Composition ◽  
Dark Green

AbstractNodules (coarse-grain “plutonic” rocks) were collected from the ca. 20 ka Pomici di Base (PB)-Sarno eruption of Mt. Somma-Vesuvius, Italy. The nodules are classified as monzonite-monzogabbro based on their modal composition. The nodules have porphyrogranular texture, and consist of An-rich plagioclase, K-feldspar, clinopyroxene (ferroan-diopside), mica (phlogopite-biotite) ± olivine and amphibole. Aggregates of irregular intergrowths of mostly alkali feldspar and plagioclase, along with mica, Fe-Ti-oxides and clinopyroxene, in the nodules are interpreted as crystallized melt pockets.Crystallized silicate melt inclusions (MI) are common in the nodules, especially in clinopyroxenes. Two types of MI have been identified. Type I consists of mica, Fe-Ti-oxides and/or dark green spinel, clinopyroxene, feldspar and a vapor bubble. Volatiles (CO2, H2O) could not be detected in the vapor bubbles by Raman spectroscopy. Type II inclusions are generally lighter in color and contain subhedral feldspar and/or glass and several opaque phases, most of which are confirmed to be oxide minerals by SEM analysis. Some of the opaque-appearing phases that are below the surface may be tiny vapor bubbles. The two types of MI have different chemical compositions. Type I MI are classified as phono-tephrite — tephri-phonolite — basaltic trachy-andesite, while Type II MI have basaltic composition. The petrography and MI geochemistry led us to conclude that the nodules represent samples of the crystal mush zone in the active plumbing system of Mt. Somma-Vesuvius that were entrained into the upwelling magma during the PB-Sarno eruption.

Acoustic wave propagation in composite fluid‐saturated media

Geophysics ◽  
1989 ◽  
Vol 54 (12) ◽  
pp. 1554-1563 ◽  
Author(s):  
J. David Keller
Keyword(s):  
Wave Propagation ◽  
Shear Wave ◽  
Wave Attenuation ◽  
Composite Model ◽  
Coarse Grained ◽  
Stress Wave Propagation ◽  
Type I ◽  
Type Ii ◽  
Saturated Media ◽  
Sand Size

Biot’s linear model of stress‐wave propagation in a fluid‐saturated elastic framework is combined with a linear theoretical description of an inelastic frame to describe fluid‐saturated media in terms of a composite model. The composite model, the Constant Q (CQ) model, assumes an inelastic frame with frequency‐dependent complex elastic moduli and results in a frame response that is causal with Q exactly independent of frequency. The influence of frame inelasticity on the composite‐model Type I (compression), Type II, and shear‐wave attenuation response is found to be greatest for high and low frequencies, considering a frequency range of [Formula: see text]. The model is most sensitive to variations in permeability and pore‐size parameter for both attenuation and phase‐velocity responses. Parameter variations showed little effect on shear‐wave attenuation for a fine to course sand‐size frame matrix, indicating a fluid mechanism is responsible for the influence seen in Type I and Type II attenuations. The CQ model results fit the experimentally measured values of Type I attenuation and velocity for a fully saturated fine‐grained frame material (clay‐silt size grains) and a fully saturated coarse‐grained frame material (fine to coarse sand‐size grains). For Type I velocity, the experimentally observed dispersion clearly distinguishes the CQ model as superior to composite models that include a nondispersive frame, since such models predict very little dispersion due only to interpore fluid mechanisms.

scholarly journals Binding of Ca2+-Independent C2 Domains to Lipid Membranes: a Multi-Scale Molecular Dynamics Study

2020 ◽  
Author(s):  
Andreas Haahr Larsen ◽  
Mark S.P. Sansom
Keyword(s):  
Molecular Dynamics ◽  
Lipid Bilayers ◽  
Md Simulations ◽  
Multiscale Simulation ◽  
Coarse Grained ◽  
Type I ◽  
Type Ii ◽  
Binding Modes ◽  
C2 Domains ◽  
Anionic Lipids

AbstractC2 domains facilitate protein-lipid interaction in cellular recognition and signalling processes. They possess a β-sandwich structure, with either type I or type II topology. C2 domains can interact with anionic lipid bilayers in either a Ca2+-dependent or a Ca2+-independent manner. The mechanism of recognition of anionic lipids by Ca2+-independent C2 domains is incompletely understood. We have used molecular dynamics (MD) simulations to explore the membrane interactions of six Ca2+– independent C2 domains, from KIBRA, PI3KC2α, RIM2, PTEN, SHIP2, and Smurf2. In coarse grained MD simulations these C2 domains bound to lipid bilayers, forming transient interactions with zwitterionic (phosphatidylcholine, PC) bilayers compared to long lived interactions with anionic bilayers also containing either phosphatidylserine (PS) or PS and phosphatidylinositol bisphosphate (PIP2). Type I C2 domains bound non-canonically via the front, back or side of the β sandwich, whereas type II C2 domains bound canonically, via the top loops (as is typically the case for Ca2+-dependent C2 domains). C2 domains interacted strongly (up to 120 kJ/mol) with membranes containing PIP2 causing the bound anionic lipids to clustered around the protein. The C2 domains bound less strongly to anionic membranes without PIP2 (<50 kJ/mol), and most weakly to neutral membranes (<33 kJ/mol). Productive binding modes were identified and further analysed in atomistic simulations. For PTEN and SHIP2, CG simulations were also performed of the intact enzymes (i.e. phosphatase domain plus C2 domain) with PIP2-contating bilayers and the roles of the two domains in membrane localization were compared. From a methodological perspective, these studies establish a multiscale simulation protocol for studying membrane binding/recognition proteins, capable of revealing binding modes alongside details of lipid binding affinity and specificity.

P-T-fluid conditions of mineral equilibria in garnet-biotite crustal xenoliths from the Yubileinaya and Sytykanskaya kimberlite pipes, Yakutian kimberlite province.

2021 ◽  
Author(s):  
Natalia Seliutina ◽  
Oleg Safonov ◽  
Vasiliy Yapaskurt ◽  
Dmitry Varlamov ◽  
Igor Sharygin ◽  
...  
Keyword(s):  
Water Activity ◽  
Siberian Craton ◽  
Database Systems ◽  
Potassium Feldspar ◽  
Coarse Grained ◽  
Chemical Compositions ◽  
Exchange Reactions ◽  
Russian Science ◽  
Isotopic Evidence ◽  
Crustal Xenoliths

&lt;p&gt;This study provides the results of research of the garnet-biotite crustal xenoliths from the Yubileinaya (372&amp;#177;4.8 Ma) and Sytykanskaya (363&amp;#177;13 Ma) kimberlite pipes of the Alakit-Markhinsky field (Siberian craton). Isotopic evidence on zircons from similar crustal xenoliths (Grt+Bt+Pl+Kfs+Qtz&amp;#177;Scp) showed Archean Hf model ages (TDM = 3.13-2.5 Ga) and thus indicated that most of the lower and middle crust beneath the Markha terrane was produced in the Archean time (Shatsky et al., 2016).&lt;/p&gt;&lt;p&gt;The xenoliths are represented by the assemblage Grt+Bt+Pl+Kfs&amp;#177;Opx. Quartz is present only as rare inclusions in garnets. The rocks are coarse-grained, slightly foliated with garnets porphyroblasts of up to 5 cm in size. A spectacular feature of the rocks is an abundance of K-feldspar. Garnet grains are almost compositionally homogeneous, although they show a rimward decrease of the Mg and Ca contents indicating exchange reactions during cooling. Biotites are characterized by high F increasing from 1.5 wt.% in cores up to 2.2 wt.% in rims, as well as TiO&lt;sub&gt;2&lt;/sub&gt; up to 7.8 wt.%, which is typical for high-grade rocks. Orthopyroxene (up to 5.5 wt. % Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;) relics are preserved both as inclusions in garnet and as individual grains in the rock matrix. Plagioclase occurs both as separate grains and as lamellae in potassium feldspar.&lt;/p&gt;&lt;p&gt;The bulk chemical compositions correspond to a metagraywacke. The REE spectra in these rocks are rather flat with slight enrichment in LREE. All the studied rocks are characterized by a distinct negative Eu anomaly (Eu/Eu* = 0.31-0.45).&lt;/p&gt;&lt;p&gt;Calculations using the PERPLEX software version 6.7.6 (Connolly, 2005) for Mg and Ca in Grt, Mg in Bt, and Ca in Pl indicated temperatures 630-730&amp;#176;C and pressures 5.8-7.2 kbar for the rocks. However, equilibria involving Al&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; in orthopyroxene corresponds to temperatures of 750-800&lt;sup&gt;o&lt;/sup&gt;&amp;#1057; at a similar pressure. It indicates that metamorphism of the garnet-biotite rocks reached higher temperatures, but they were actively modified later during cooling and insignificant decompression (by about 1 kbar). Calculations using the TWQ software version 2.3 (Berman, 2007) indicate consistent temperatures 610-680&amp;#176;C for the garnet-orthopyroxene and 640-690&lt;sup&gt;o&lt;/sup&gt;C for garnet-biotite Mg-Fe exchange equilibria. Calculations using the Grs+2Prp+Kfs+H&lt;sub&gt;2&lt;/sub&gt;O=Phl+3En+3An equilibrium demonstrated water activity below 0.1. Such low water activity could indicate an influence of highly concentrated alkaline Cl-F-bearing brines. This assumption is confirmed by extensive development of potassium feldspar, absence of quartz in the matrix, and elevated Cl contents of biotite, 0.1-0.3 wt. % at high #Mg (&gt;0.7) and F content.&lt;/p&gt;&lt;p&gt;&lt;em&gt;The study is supported by the Russian Science Foundation project 18-17-00206.&lt;/em&gt;&lt;/p&gt;&lt;p&gt;&lt;strong&gt;&amp;#160;&lt;/strong&gt;&lt;strong&gt;References &lt;/strong&gt;&lt;/p&gt;&lt;p&gt;Berman, R. G. (2007). winTWQ (version 2.3): a software package for performing internally-consistent thermobarometric calculations.&amp;#160;Geological survey of Canada, open file,&amp;#160;5462, 41.&lt;/p&gt;&lt;p&gt;Connolly, T. M., &amp; Begg, C. E. (2005).&amp;#160;Database systems: a practical approach to design, implementation, and management. Pearson Education.&lt;/p&gt;&lt;p&gt;Shatsky, V. S., Malkovets, V. G., Belousova, E. A., ... &amp; O&amp;#8217;Reilly, S. Y. (2016). Tectonothermal evolution of the continental crust beneath the Yakutian diamondiferous province (Siberian craton): U&amp;#8211;Pb and Hf isotopic evidence on zircons from crustal xenoliths of kimberlite pipes.&amp;#160;Precambrian Research,&amp;#160;282, 1-20.&lt;/p&gt;

scholarly journals Larval strigeoid trematodes in anurans from southern Nigeria

2014 ◽  
Vol 51 (4) ◽  
pp. 318-322 ◽  
Author(s):  
O. Edo-Taiwo ◽  
E. Ovwah ◽  
A. Imasuen ◽  
M. Aisien
Keyword(s):  
National Park ◽  
West African ◽  
Type I ◽  
Type Ii ◽  
African Countries ◽  
Public Health Importance ◽  
Cyst Type ◽  
Monoculture Plantation ◽  
Southern Nigeria ◽  
Tree Frogs

AbstractAnurans from locations in the rainforest, derived savannah and a monoculture plantation in Nigeria were examined for infection with strigeoid trematode larvae. Two types of metacercarial cysts were recovered. The cyst type I (rounded with fringe projections) occurred in tree frogs from the Okomu National Park, at Usen (derived savannah) and the Okomu Oil Palm Plantation (OOPP). The cyst type II was recovered from A. dorsalis and Ptychadena bibroni collected at OOPP. The cysts were ovoid in shape, devoid of projections at the fringes and were not subject to trypsin action. An unencysted metacercaria was found in A. dorsalis collected at Usen while mesocercaria of Alaria occurred in the lungs of Pty. pumilio at OOPP. The finding of Alaria mesocercaria in Pty. pumilio is of public health importance in view of the fact that many ranid frogs are consumed in Nigeria and other West African countries.

Petrology and oxygen-isotope geochemistry of the Yamba Lake kimberlite rocks, N.W.T.

2000 ◽  
Vol 37 (7) ◽  
pp. 1053-1071 ◽  
Author(s):  
Pauline Orr ◽  
Robert W Luth
Keyword(s):  
Major Element ◽  
Isotope Geochemistry ◽  
Isotopic Fractionation ◽  
Kimberlite Pipe ◽  
Spinel Lherzolite ◽  
Garnet Lherzolite ◽  
Slave Province ◽  
Low Concentrations ◽  
Subducted Oceanic Crust ◽  
Indicator Minerals

The Torrie, Sputnik, and Eddie kimberlite rocks, located near Yamba Lake, central Slave province, N.W.T., are volcaniclastic, macrocrystic, heterolithic, olivine-rich tuff, and olivine-rich tuff breccia. Torrie and Sputnik kimberlite rocks contain pyroxene and garnet xenocrysts and megacrysts with major-element compositions consistent with derivation mostly from disaggregated garnet lherzolite, with subordinate contributions from eclogite, spinel lherzolite, garnet harzburgite, and websterite. The presence of primary groundmass phlogopite and compositionally evolved spinel, and the absence of mantle xenocrysts, xenoliths, and megacrystic ilmenite distinguish the Eddie kimberlite pipe from the other two kimberlite pipes. Large variations in δ18O of garnet and clinopyroxene in xenocrysts and xenoliths (+3.98 to +6.36‰), nonequilibrium intermineral isotopic fractionation, and major-element heterogeneity are interpreted as resulting from infiltration of fluids or melts produced by dehydration or melting of subducted oceanic crust into overlying peridotite. Although the timing is unconstrained for the xenocysts, the xenolith must have experienced this metasomatic interaction shortly before entrainment in the kimberlite. Variable δ18O values for magnesian ilmenite are also interpreted to result indirectly from such metasomatic activity in the mantle as well. The Torrie and Sputnik kimberlite rocks have low concentrations of diamond indicator minerals consistent with their low-diamond grades. These kimberlite rocks did not sample a significant amount of garnet harzburgite, the rock type commonly associated with high-diamond grades in other kimberlite rocks. Furthermore, metasomatism just prior to kimberlite eruption may have caused the resorption of any diamond present.

scholarly journals Tourmaline as a Recorder of Ore-Forming Processes in the Xuebaoding W-Sn-Be Deposit, Sichuan Province, China: Evidence from the Chemical Composition of Tourmaline

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 438
Author(s):  
Xinxiang Zhu ◽  
Markus B. Raschke ◽  
Yan Liu
Keyword(s):  
Chemical Composition ◽  
Aqueous Fluid ◽  
Sichuan Province ◽  
Coarse Grained ◽  
Gangue Mineral ◽  
Type I ◽  
Type Ii ◽  
Type Iii ◽  
Wide Range ◽  
Granite Type

The Xuebaoding W-Sn-Be deposit located in the Songpan-Ganze Orogenic Belt (Sichuan Province, China) is a hydrothermal deposit with less developed pegmatite stage. The deposit is famous for the coarse-grained crystals of beryl, scheelite, cassiterite, apatite, fluorite, muscovite, and others. The orebody is spatially associated with the Pankou and Pukouling granites hosted in Triassic marbles and schists. The highly fractionated granites are peraluminous, Li-Rb-Cs-rich, and related to W-Sn-Be mineralization. The mineralization can chiefly be classified based on the wallrock and mineral assemblages as muscovite and beryl in granite (Zone I), then beryl, cassiterite and muscovite at the transition from granite to triassic strata (Zone II), and the main mineralized veins composed of an assemblage of beryl, cassiterite, scheelite, fluorite, and apatite hosted in metasedimentary rock units of marble and schist (Zone III). Due to the stability of tourmaline over a wide range of temperature and pressure conditions, its compositional variability can reflect the evolution of the ore-forming fluids. Tourmaline is an important gangue mineral in the Xuebaoding deposit and occurs in the late-magmatic to early-hydrothermal stage, and can thus be used as a proxy for the fluid evolution. Three types of tourmalines can be distinguished: tourmaline disseminations within the granite (type I), tourmaline clusters at the margin of the granite (type II), and tourmalines occurring in the mineralized veins (type III). Based on their chemical composition, both type I and II tourmalines belong to the alkali group and to the dravite-schorl solid solution. Type III tourmaline which is higher in X-site vacancy corresponds to foitite and schorl. It is proposed that the weakly zoned type I tourmalines result from an immiscible boron-rich aqueous fluid in the latest stage of granite crystallization, that the type II tourmalines showing skeletal texture directly formed from the undercooled melts, and that type III tourmalines occurring in the mineralized veins formed directly from the magmatic hydrothermal fluids. Both type I and type II tourmalines show similar compositional variations reflecting the highly fractionated Pankou and Pukouling granites. The higher Ca, Mg, and Fe contents of type III tourmaline are buffered by the composition of the metasedimentary host rocks. The decreasing Na content (<0.8 atoms per formula unit (apfu)) and increasing Fe3+/Fe2+ ratios of all tourmaline samples suggest that they precipitated from oxidized, low-salinity fluids. The decreasing trend of Al content from type I (5.60–6.36 apfu) and type II (6.01–6.43 apfu) to type III (5.58–5.87 apfu) tourmalines, and associated decrease in Na, may be caused by the crystallization of albite and muscovite. The combined petrographic, mineralogical, and chemical characteristics of the three types of tourmalines thus reflect the late-magmatic to early-hydrothermal evolution of the ore-forming fluids, and could be used as a geochemical fingerprint for prospecting W-Sn-Be mineralization in the Xuebaoding district.

Heat-Etching with a Bullivant Type II Simple Freeze-Cleave Device

1970 ◽  
Vol 28 ◽  
pp. 106-107 ◽  
Author(s):  
Ronald S. Weinstein ◽  
N. Scott McNutt
Keyword(s):  
New Zealand ◽  
General Hospital ◽  
Massachusetts General Hospital ◽  
Type I ◽  
Type Ii ◽  
Collaborative Effort ◽  
Temperature And Pressure ◽  
The University

The Type I simple cold block device was described by Bullivant and Ames in 1966 and represented the product of the first successful effort to simplify the equipment required to do sophisticated freeze-cleave techniques. Bullivant, Weinstein and Someda described the Type II device which is a modification of the Type I device and was developed as a collaborative effort at the Massachusetts General Hospital and the University of Auckland, New Zealand. The modifications reduced specimen contamination and provided controlled specimen warming for heat-etching of fracture faces. We have now tested the Mass. General Hospital version of the Type II device (called the “Type II-MGH device”) on a wide variety of biological specimens and have established temperature and pressure curves for routine heat-etching with the device.

Labelling of non-A, non-B hepatitis infected chimpanzee hepatocytes with nuclease-gold conjugates

1984 ◽  
Vol 42 ◽  
pp. 250-251
Author(s):  
G. D. Gagne ◽  
M. F. Miller ◽  
D. A. Peterson
Keyword(s):  
Endoplasmic Reticulum ◽  
Experimental Infection ◽  
Uranyl Acetate ◽  
Type I ◽  
Cellular Injury ◽  
Type Ii ◽  
Tubular Structures ◽  
Type Iii ◽  
Type Iv ◽  
Infected Chimpanzee

Experimental infection of chimpanzees with non-A, non-B hepatitis (NANB) or with delta agent hepatitis results in the appearance of characteristic cytoplasmic alterations in the hepatocytes. These alterations include spongelike inclusions (Type I), attached convoluted membranes (Type II), tubular structures (Type III), and microtubular aggregates (Type IV) (Fig. 1). Type I, II and III structures are, by association, believed to be derived from endoplasmic reticulum and may be morphogenetically related. Type IV structures are generally observed free in the cytoplasm but sometimes in the vicinity of type III structures. It is not known whether these structures are somehow involved in the replication and/or assembly of the putative NANB virus or whether they are simply nonspecific responses to cellular injury. When treated with uranyl acetate, type I, II and III structures stain intensely as if they might contain nucleic acids. If these structures do correspond to intermediates in the replication of a virus, one might expect them to contain DNA or RNA and the present study was undertaken to explore this possibility.

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