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61.
Fe-Mn partitioning between garnet and ilmenite: experimental calibration and applications 总被引:2,自引:0,他引:2
Mark I. Pownceby Victor J. Wall Hugh St. C. O'Neill 《Contributions to Mineralogy and Petrology》1987,97(1):116-126
A new mineralogic geothermometer based on the partitioning of Fe and Mn between garnet and ilmenite has been calibrated by reversal experiments in the P-T range 600–900° C, 2 and 5 kbars and for fO2=QFM. The results constitute a sensitive geothermometer applicable over a broad range of composition and conditions. Garnetilmenite thermometry has advantages relative to existing geothermometers because of its accurate calibration, marked temperature sensitivity and the chemical and structural simplicity of the crystalline solutions involved. Application to natural assemblages reveals that the garnet-ilmenite geothermometer yields temperatures that agree well with other estimates. The reactivity of, and relatively rapid Fe-Mn diffusion in ilmenite may lead to retrograde resetting of high temperature partition values, but these factors may be useful for estimating rock cooling rates. Analysis of the experimental data indicates minor positive deviations from ideality for Fe-Mn garnets and ilmenites. Absolute magnitudes of interaction parameters (W
AB) derived from a regression analysis are subject to considerable uncertainty. The partition coefficient is, however, strongly dependent on the difference between solution parameters. These differences are well constrained with a magnitude of W
FeMn
ilm
–W
FeMn
gar
300 cal mol–1. The accuracy and applicability of garnet-ilmenite thermometry will improve with the availability of better thermodynamic data for garnet crystalline solutions.Abbreviations and symbols used in text
R
universal gas constant (cal/mol/°K)
-
T
absolute temperature (°K or °C)
-
P
pressure (kbars)
- V
0
volume change of reaction (1)
-
H
1, T
0
standard state enthalpy change of reaction (1) at 1 bar and the T of interest, in cal/mole
-
S
T
0
entropy change of reaction (1) at T of interest, in cal/mole/°K
-
G
P,T
0
standard free energy change of reaction (1) at the T and P of interest, in cal/mole
-
distribution coefficient for Fe-Mn partitioning between garnet and ilmenite
-
K
apparent equilibrium coefficient for reaction (1)
-
i
j
activity of component i in phase j
-
W
A-B
binary A-B interaction (Margules) parameter
-
gar
garnet
-
ilm
ilmenite
-
biot
biotite
-
ol
olivine
-
opx
orthopyroxene 相似文献
62.
Lawrence M. Anovitz Allan H. Treiman Eric J. Essene Bruce S. Hemingway Edgar F. Westrum Victor J. Wall Ramón Burriel Steven R. Bohlen 《Geochimica et cosmochimica acta》1985,49(10):2027-2040
Low temperature adiabatic calorimetry and high temperature differential scanning calorimetry have been used to measure the heat-capacity of ilmenite (FeTiO3) from 5 to 1000 K. These measurements yield S2980 = 108.9 J/(mol · K). Calculations from published experimental data on the reduction of ilmenite yield Δ2980(I1) = ?1153.9 kJ/(mol · K). These new data, combined with available experimental and thermodynamic data for other phases, have been used to calculate phase equilibria in the system Fe-Ti-O. Calculations for the subsystem Ti-O show that extremely low values of are necessary to stabilize TiO, the mineral hongquiite reported from the Tao district in China. This mineral may not be TiO, and it should be re-examined for substitution of other elements such as N or C. Consideration of solid-solution models for phases in the system Fe-Ti-O allows derivation of a new thermometer/oxybarometer for assemblages of ferropseudobrookite-pseudobrookitess and hematite-ilmenitess. Preliminary application of this new thermometer/oxybarometer to lunar and terrestrial lavas gives reasonable estimates of oxygen fugacities, but generally yields subsolidus temperatures, suggesting re-equilibration of one or more phases during cooling. 相似文献
63.
In high Ti basanites from the Vogelsberg 1996 drillhole distinct variations in the field dependence of AC magnetic susceptibility correlate with compositional variations of titanomagnetite, as determined by temperature dependence of magnetic susceptibility. Curie temperatures for the basanites are in the range of 240 to 525°C. The field dependence reaches up to 20% for measurements in 30 A/m and 300 A/m AC field amplitude. It is demonstrated that two-field magnetic susceptibility measurements can prevail information about compositional changes of titanomagnetite and therefore support the interpretation of magnetic susceptibility logs from drillcores of basaltic rock suites. 相似文献
64.
Jason K Blackburn rew Curtis Frances Currin Mujica Farrell Jones Patricia Dorn Rosamond Coates 《Transactions in GIS》2008,12(2):249-265
This article describes a web‐based data entry and GIS‐driven mapping system designed for an ethnographic and entomological survey of Chagas’ disease, an emerging zoonotic disease, and Triatoma dimidiata, a primary vector, in the Los Tuxtlas region of Veracruz, Mexico. To better understand this disease in the region, a collaborative, multi‐disciplinary study was initiated to conduct a spatial investigation of T. dimidiata and a community‐by‐community survey of local perceptions of the disease. In order to facilitate such a collaborative effort the CODES‐GIS was developed. This system allows for (near) real‐time mapping, analyses, disease reporting, and results sharing. CODES‐GIS provides a framework for a research team working in a remote area with limited technology, software, or GIS expertise to benefit from (near) real‐time spatial analyses performed at collaborating institutions. The system is bi‐directional, where field personnel can upload data to the system for field‐based map production. Likewise, laboratory personnel can upload diagnostics data for viewing by field personnel. In this way, the system provides a virtual link between the field and the laboratory to increase the speed at which results are returned to the local community. The CODES‐GIS is described along with a selection of study results. 相似文献
65.
High-resolution magnetograph observations of the polar magnetic fields have been obtained at intervals of time since the end of 1986 at Big Bear Solar Observatory. The Big Bear data differ from the low-resolution, full-disk magnetograph observations in that the 2 arc sec resolution makes it possible to resolve concentrated field upward of 100 G. The purpose of this ongoing observation is to examine the evolution of polar fields during the expected polarity reversal as cycle 22 passes its maximum phase, and secondly, to study the polar magnetic field: its true field strength, distribution, and how it compares to other parts of the quiet Sun.We find that the >70° net polar flux of both poles has not reversed as of the end of 1989. However, in the lower latitudes of both poles, 50° to 70°, there are signs reminiscent of those preceding the reversals in cycles 19 and 20. These include: decreasing field intensity in the old polarity fluctuations in net flux between the old and new polarities.We find that the net average longitudinal polar fields (above 50°) are 1–2 G, in agreement with results found in cycles 19 and 20. For individual elements, however, the strongest observed field strength poleward of 70° is over 100 G.We compare the polar fields with the equatorial limb as a function of latitute and longitude, respectively, and find the polar fields are comparable to (or stronger than) the quiet equatorial limb. When the observed mean flux density of the polar field as a function of latitude is corrected for limb-darkening and projection effects (assuming the field is radial), the result is nearly constant. These results suggest that despite the high latitudes, the polar fields have field strength and distribution similar to other parts of the quiet Sun. 相似文献
66.
The outcomes and forms of urbanization and modernization in China following the reform and opening of the late 1970s have attracted extensive attention and competing interpretations in scholarly documentation. This paper focuses on Hainan Island, established in 1988 as the biggest special economic zone in China. Since then, considerable inflows of human as well as speculative capital have led to rapid real estate, in particular tourism-related, development. While urban expansion and improvements have been encouraged, the ongoing over-building, unregulated conversion of land use and degradation of the urban environment present serious social and economic problems. This paper summarizes the trajectory, causal factors and outcomes of this urban growth and consequent planning problems that make the island an atypical case in China's urbanization experience. We argue that the establishment of a practical framework combining socioeconomic planning, land use planning, and the management of both, is crucial to achieve sustainable growth for this transitional economy. 相似文献
67.
68.
Frances P. Wilkerson Richard C. Dugdale Victoria E. Hogue Albert Marchi 《Estuaries and Coasts》2006,29(3):401-416
San Francisco Bay has been considered an HNLC or HNLG (high nutrient low chlorophyll or low growth) region with nonlimiting concentrations of inorganic nutrients yet low standing stocks of phytoplankton. Most of the studies leading to this conclusion come from the South Bay and little is known about nutrient processes and phytoplankton productivity in the northern and central parts of the estuary. Data collected over 3 yr (1999–2003) in Suisun, San Pablo, and Central Bays describe the availability of dissolved inorganic nitrogen (DIN), silicate, and phosphate and the seasonal variability in phytoplankton abundance. Rate measurements of fractionated nitrogen productivity provide the relative contributions of different forms of DIN (ammonium and nitrate) and different sized phytoplankton to the development of seasonal phytoplankton blooms. Regional differences in bloom dynamics are observed with Suisun Bay, the least saline, highest nutrient, most turbid region having less phytoplankton biomass and productivity than San Pablo and Central Bays, except in the abnormally wet spring of 2000. Spring blooms in San Francisco Bay are driven primarily by high rates of nitrate uptake by larger phytoplankton cells following a period of increased ammonium uptake that depletes the ambient ammonium. The smaller occasional fall blooms are apparently flueled mostly by ammonium uptake by small sized phytoplankton. The data suggest that the HNLC condition in the northern and central parts of San Francisco Bay is due primarily to light availability modulated by the interaction between ammonium and nitrate, and the relative amounts of the two forms of the DIN pool available to the phytoplankton. 相似文献
69.
Interactive analysis of the spatial distribution of disease using a geographic information systems 总被引:1,自引:0,他引:1
Geographic information systems (GIS) provide a variety of tools for the manipulation and display of public health data. Few,
however, enable users to interactively evaluate hypotheses on spatial trends in disease risk that may be suggested by maps
of measures of disease impact. We addressed this limitation by developing a seamless interface between a commercial GIS and
a suite of spatial analysis algorithms. Users of the system can utilize the GIS's capability to interactively select and manipulate
geographically referenced data and, through a series of pull-down menus, apply a variety of exploratory analysis methods to
this information. In the presented application, we illustrate this capability by including algorithms for the reduction of
random noise in observed incidence rates, for the detection of unusual aggregations of disease events, and for the statistical
evaluation of inferences drawn from spatial trends. We demonstrate this application by examining lung cancer mortality in
the state of Ohio.
Received: 22 September 1999 / Accepted: 8 March 2000 相似文献
70.