Spectroscopic photoacoustic imaging has the potential to discriminate between normal and lipid-rich atheromatous areas of arterial tissue by exploiting the differences in the absorption spectra of ...lipids and normal arterial tissue in the 740 to 1400 nm wavelength range. Identification of regions of high lipid concentration would be useful to identify plaques that are likely to rupture (vulnerable plaques). To demonstrate the feasibility of visualizing lipid-rich plaques, samples of human aortas were imaged in forward mode, at wavelengths of 970 and 1210 nm. It was shown that the structure of the arterial wall and the boundaries of lipid-rich plaques obtained from the photoacoustic images were in good agreement with histology. The presence of lipids was also confirmed by comparing the photoacoustic spectra (740 to 1400 nm) obtained in a region within the plaque to the spectral signature of lipids. Furthermore, a lipid-rich plaque was successfully imaged while illuminating the sample through 2.8 mm of blood demonstrating the possibility of implementing the photoacoustic technique in vivo.
Magnetite–melt HFSE partitioning Nielsen, Roger L.; Beard, James S.
Chemical geology,
03/2000, Letnik:
164, Številka:
1
Journal Article
Recenzirano
Results from doped, hydrous experiments on natural mafic-to intermediate-composition lavas at 2–5 kbar pressure were combined with existing 1 atm data to evaluate the effects of composition and ...temperature on the partitioning behavior of the high field strength elements (HFSE), Zr, Nb, Ta and Hf between magnetite and natural silicate melts. Magnetite composition was found to be the strongest controlling factor on partitioning behavior. The partition coefficients (
D) for Zr, Nb, Hf, and Ta correlate with
D
Ti, Ti and Al content of the magnetite, temperature and pressure. The partition coefficients for the HFSE are similar to one another for any given magnetite–melt pair, but range from <0.02 in Cr, Al-rich magnetites and chromites to >2 in titanomagnetite. In addition, the relationship between Ti and the HFSE changes as a function of pressure and temperature, with the HFSE becoming more incompatible relative to Ti at lower temperatures and/or higher pressures. This change in the relationship between
D
Ti and
D
HFSE with temperature and pressure means that the expressions presented in Nielsen et al. (1994) Nielsen, R.L., Forsythe, L.M., Gallaghan, W.E., Fisk, M.R., 1994. Major and trace element magnetite–melt partitioning. Chem. Geol. 117, 167–191. are not valid for hydrous, aluminous systems. Expressions were derived to describe the relationship between
D
HFSE and temperature, pressure, Fe
2+/Mg exchange, Ti/Al ratio of the magnetite, and
D
Ti. These expressions reproduce the input data within 35–50% (1
σ) over a range extending from highly incompatible to compatible (<0.02–3.0). This internal precision represents ∼3–4% of the observed range of partition coefficients. These patterns of behavior are consistent with the observed miscibility gap between the Al, Cr spinel group end members and ülvospinel and magnetite.
Minerals of the Hutter mine Beard, James S; Tracy, Robert J; Williams Henika
Rocks & minerals,
200210, Letnik:
77, Številka:
5
Journal Article
Recenzirano
In the spring of 1996, construction work associated with recontouring old mine dumps at the nineteenth-century Hutter iron mine in Pittsylvania County VA exposed a small dump composed almost entirely ...of manganese-rich rocks. The deposit is thought to have evolved by deformation and metamorphism of stratabound volcanogenic iron formations similar to those described from the Lokken deposit of the Trondheim district in Norway or the Besshi deposit in the Skikoku district of Japan.
Plutonic rocks intrusive into the late Paleozoic Tetelna Formation of southern Alaska are the underpinnings of the late Paleozoic Skolai arc of the Wrangellia Terrane. There are four groups of ...intrusive rocks within the Skolai arc: (1) Gabbro-diorite plutons that contain gabbroic to anorthositic cumulates along with a differentiated series of gabbros and diorites of basaltic to andesitic composition; (2) Silicic intrusions including tonalite, granodiorite, and granite; (3) Monzonitic to syenitic plutonic rocks of the Ahtell complex and related dikes and sills; (4) Fault-bounded bytownite anorthosite of uncertain age and association. These anorthosites may be related to post-Skolai, Nikolai Greenstone magmatism. The silicic rocks yield discordant U-Pb zircon ages of 290-320 Ma (early to late Pennsylvanian). Relative age relations suggest that the oldest intrusive rocks are the gabbro-diorite plutons, the youngest are the monzonitic rocks, and that the silicic rocks span this range. The gabbro-diorite plutons are similar to gabbroic plutonic rocks in modern and other ancient island arc complexes. They record the differentiation of calc-alkaline basalt to andesite by the fractionation of plagioclase, pyroxene, olivine, and Fe-Ti oxides. The silicic rocks do not appear to be related to either the gabbros or the monzonites. They may represent partial melts of Skolai arc crust. The monzonitic rocks of the Ahtell complex have shoshonitic chemistry. Similar shoshonitic rocks are widespread in both the Wrangellia terrane and the neighboring Alexander terrane and intrude the contact between the two. In modern oceanic arcs, shoshonitic rocks are typically associated with tectonic instability occurring during the initial stages of subduction or just prior to or during termination or flip of an established subduction zone. The nature of any tectonic instability which may have led to the cessation of subduction in the Skolai arc is unclear. Possibilities include collision of the arc with a ridge, an oceanic plateau, another arc, or a continental fragment. One possibility is that the shoshonitic magmatism marks the late Paleozoic amalgamation of Wrangellia and the Alexander terrane. The scarcity of arc rocks predating the shoshonites in the Alexander terrane supports this possibility, but structural corroboration is lacking.
Water loss from vapor-absent melting experiments with durations of 5-31 days in a piston cylinder apparatus at seven, ten and 15 kbar and 925-1,000 degrees C is discussed. Research on an amphibole ...gneiss found that the most obvious manifestation of water loss is a decrease in melt fraction and an increase in plagioclase abundance with increasing temperature.
The book identifies more than 50 categories and compiles representive listings within each area of people, things, and institutions serving the food and wine professions. Contents include who's who ...of cooking in America, specialty food restaurants, restaurant operations, alcoholic beverages, schools, home and professional kitchens, food companies, food promotion, food graphics, food publications, scientific and government information sources, and food fairs and festivals
A new locality for the Ba-rich trioctahedral mica, kinoshitalite Ba(Mg,Mn,Fe,Al)
Si
Al
(OH,F)
, has been found in a metamorphosed manganoan marble from Pittsylvania County, Virginia. Metamorphic ...grade is middle amphibolite facies, with documented P and T of 400 MPa and 575 °C. The locality is along strike not far from the well known Bald Knob, North Carolina, Mn-mineral locality, and appears to represent a silica-poorer analog of Bald Knob. The kinoshitalite occurs in a single layered hand sample containing both skarn and marble layers, and it shows significant compositional contrasts between the two lithologies. Kinoshitalite is scarce and fine-grained in manganoan marble and coexists with kutnahorite, manganoan calcite, fluorian alleghanyite, fluorian sonolite, aluminous jacobsite, and alabandite. Kinoshitalite is both more abundant and coarser-grained in skarn where it coexists with kutnahorite, tephroite, fluorian manganhumite, spessartine, jacobsite, and manganoan magnetite. A-sites in kinoshitalite in skarn are about 3/4 occupied by Ba (with the remainder mostly K), whereas in marble, Ba occupancy of A-sites exceeds 90% and most of the remainder is Ca. X
in octahedral sites is >0.6 and is higher in marble than in skarn, whereas X
is significant (>0.2) and is higher in skarn than in marble. The
Al is significantly higher in skarn kinoshitalite, as is total Tschermak content. The total Tschermak content of these barian micas (
Al + Ti + Fe
) is typical of all previously reported kinoshitalites and is significantly lower than that of clintonite and biotite. The X
of kinoshitalite in marble is significantly higher than that in skarn.
The petrogenesis of kinoshitalite at the Hutter Mine locality is unclear due to the lack of context for the single mine-dump sample in which the mineral was found and the absence of textural evidence for reactions. However, the two likeliest source minerals for Ba that have been found in the deposit are barite and BaCa(CO
(probably barytocalcite). One hypothetical reaction to produce kinoshitalite involves decarbonation, in which BaCa(CO
, rhodochrosite, Mn-garnet, and aqueous fluid react to form kinoshitalite, tephroite (or an Mn-humite), calcite, and CO
. A second potential reaction to form kinoshitalite involves barite, Mn-garnet, tephroite, and aqueous fluid as reactants, and kinoshitalite, alabandite, jacobsite, SiO
, and O
as products.
The Hutter Mine locality, Pittsylvania County, Virginia, is a metamorphosed magnetite deposit, with substantial development of subsidiary manganoan marble, that occurs within Latest Precambrian or ...Early Paleozoic sillimanite-grade pelitic schists. Manganese oxides and spinels at the Hutter Mine include manganosite (MnO) (coexisting with hausmannite and jacobsite) as well as spinels rich in jacobsite (FeMn
), magnetite (Fe
), and galaxite (MnAl
), and a variety of intermediate solid solutions between these three end-members. Several samples contain spinels that exhibit substantial miscibility along the jacobsite-galaxite and jacobsite-magnetite joins. Magnetite-galaxite solid solution is, by comparison, very limited. Coexisting manganoan spinels within the jacobsitegalaxite- magnetite ternary system include jacobsite-rich varieties with galaxite <65 (normalized to glx + mag + jac = 100) that coexist with Mg-Zn-bearing galaxite-rich spinel with galaxite >75. However, the wide range of spinel compositions at the Hutter Mine largely reflects compositional variability in the host rock. In a skarn reaction zone between Fe-rich, quartz-bearing amphibolites and Si-poor, Mn-rich marbles, the galaxite content of spinel drops from 60% to near zero as silica activity increases over a 5 mm interval. In this same reaction zone, magnetite content of spinel increases from about 10 to 95%, but over a narrower interval (about 2 mm). Total variation in spinel composition in this reaction zone is nearly the same as that seen over the entire suite of Hutter Mine samples.
Both regional metamorphic geology and thermobarometry on local pelite samples indicates that T
at the Hutter Mine was 550-600 °C. Manganosite formed by the decarbonation of Mn-rich carbonate in the presence of a CO
-poor (X
≤ 0.01) fluid having log a
< -3.0. Oxygen fugacity in the manganosite-bearing sample was buffered by coexisting manganosite and hausmannite, placing f
within the magnetite stability field at peak T. This result is consistent with the occurrence of magnetite as the principal ore at Hutter.
The extensive miscibility observed along the jacobsite-galaxite join requires reexamination of miscibility gaps proposed in previous studies. We suggest that the wide compositional gaps found in previous studies reflect a variety of chemical factors of which silica activity is the most critical. In particular, the large range of silica activities observed in Hutter Mine rocks stabilizes spinels with a wide range in galaxite content. The crests of both the jacobsite-galaxite and jacobsite-magnetite two-phase regions appear to occur at relatively low temperatures, probably below 600 °C.
