Empirical calibration of oxygen isotope fractionation in zircon

New empirical calibrations for the fractionation of oxygen isotopes among zircon, almandine-rich garnet, titanite, and quartz are combined with experimental values for quartz-grossular. The resulting A-coefficients (‰K²) are:

	Zrc	Alm	Grs	Ttn
Qtz	2.64	2.71	3.03	3.66
Zrc		0.07	0.39	1.02
Alm			0.32	0.95
Grs				0.63

Full-size table

     

Thermodynamic properties of anhydrous smectite MX-80, illite IMt-2 and mixed-layer illite-smectite ISCz-1 as determined by calorimetric methods. Part I: Heat capacities, heat contents and entropies

The heat capacities of the anhydrous international reference clay minerals, smectite MX-80, illite IMt-2 and mixed-layer illite-smectite ISCz-1, were measured by low temperature adiabatic calorimetry and differential scanning calorimetry, from 6 to 520 K (at 1 bar). The samples were chemically purified and Na-saturated. Dehydrated clay fractions <2 μm were studied. The structural formulae of the corresponding clay minerals, obtained after subtracting the remaining impurities, are K_0.026Na_0.435Ca_0.010(Si_3.612Al_0.388) (Al_1.593Mg_0.228Ti_0.011)O₁₀(OH)₂ for smectite MX-80, K_0.762Na_0.044(Si_3.387Al_0.613) (Al_1.427Mg_0.241O₁₀(OH)₂ for illite IMt-2 and K_0.530Na_0.135(Si_3.565Al_0.435)(Al_1.709Mg_0.218Ti_0.005)O₁₀(OH)₂for mixed-layer ISCz-1. From the heat capacity values, we determined the molar entropies, standard entropies of formation and heat contents of these minerals. The following values were obtained at 298.15 K and 1 bar:

	(J mol−1 K−1)	S0 (J mol−1 K−1)
Smectite MX-80	326.13 ± 0.10	280.56 ± 0.16
Illite IMt-2	328.21 ± 0.10	295.05 ± 0.17
Mixed-layer ISCz-1	320.79 ± 0.10	281.62 ± 0.15

Full-size table

     

Low-temperature heat capacities of synthetic pyrope,grossular, and pyrope60grossular40

The heat capacities of synthetic pyrope (Mg₃Al₂Si₂O₁₂), grossular (Ca₃Al₂Si₃O₁₂) and a solid solution pyrope₆₀grossular₄₀ (Mg_1.8Ca_1.2Al₂Si₃O₁₂) have been measured by adiabatic calorimetry in the temperature range 10–350 K. The samples were crystallized from glasses in a conventional piston-cylinder apparatus.The molar thermophysical properties at 298.15 K (J mol^?1 K^?1) are:

     

4.

Amino acid geochronology of raised beaches in south west Britain     

D.Q. Bowen  G.A. Sykes  Alayne Reeves  G.H. Miller  J.T. Andrews  J.S. Brew  P.E. Hare 《Quaternary Science Reviews》1985,4(4):279-318

     

5.

Crustal development in the Agnew region,Western Australia,as shown by Rb/Sr isotopic and geochemical studies     

J.A Cooper  R.W Nesbitt  J.P Platt  G.E Mortimer 《Precambrian Research》1978,7(1):31-59

Rb/Sr geochronology on a folded greenstone-granitoid complex in the Agnew area, Western Australia, yields four distinct ages of igneous activity that conform with stratigraphic and intrusive relationships. They are (using $\text{λ}{}^{87}\text{Rb}\text{= 1.42 · 10}{}^{\mathrm{?11}}\text{a}{}^{\mathrm{?1}}$, NBS 70A = 522 ppm Rb and 65.3 ppm Sr):

	Cop	So298?So0	Ho298?Ho0/T
Pyrope	325.31	266.27	47852
Grossular	333.17	260.12	47660
Py60Gr40	328.32	268.32	47990

     

6.

Pallasites—metal composition,classification and relationships with iron meteorites     

Edward R.D Scott 《Geochimica et cosmochimica acta》1977,41(3):349-360

Concentrations of Au, As, Co, Ga, Ge, Ir, Ni and W were determined in the metal of 28 different pallasites plus 6 which are probably paired, to help elucidate their origin. Most divide into two clusters:

	Ma	87Sr/86Sr initial (IR)
(1) Differentiated gabbro-granophyre from a stratigraphically old (Kathleen Valley) greenstone sequence	$\text{> 2718 ± 50}$	$\text{0.7007 ± 0.0004}$
(2) Voluminous tonalite, the Lawlers Tonalite	$\text{2652 ± 20}$	$\text{0.70152 ± 0.00012}$
	$\text{2576 ± 14}$	$\text{0.70218 ± 0.00021}$
(3) A less voluminous leucogranite, and a large complex pegmatite cutting the Perseverance nickel orebody	$\text{2588 ± 18}$	$\text{0.7624 ± 0.0068}$
(4) Aplitic leucotonalite (very minor volumes but widespread)	$\text{2474 ± 14}$	$\text{0.70193 ± 0.00012}$

     

7.

Oxygen isotope fractionations involving pyroxenes: The calibration of mineral-pair geothermometers     

Alan Matthews  Julian R. Goldsmith  Robert N. Clayton 《Geochimica et cosmochimica acta》1983,47(3):631-644

Oxygen isotope fractionations between wollastonite, diopside, jadeite, hedenbergite and water have been experimentally studied at high pressures (1<- PH₂O ≥ 24 kbar) and temperatures (400/dg ≤ T <- 800/dgC) using the three-isotope method (Matsuhisa et al., 1978). Initial ${}^{18}\text{O}{}^{16}\text{O}$ fractionations were made close to equilibrium and initial ${}^{17}\text{O}{}^{16}\text{O}$ ratios were well removed from equilibrium, allowing accurate determinations of the equilibrium ${}^{18}\text{O}{}^{16}\text{O}$ fractionations and of the extent of isotopic exchange. Scanning electron microscope and rate studies show that the wollastonite-water and diopside-water exchange reactions occur largely by solution-precipitation (Ostwald Ripening) mechanisms. Equilibrium ${}^{18}\text{O}{}^{16}\text{O}$ fractionations between water and the minerals wollastonite, diopside, and hedenbergite are in close agreement with one another, whereas significantly more positive fractionations are found for jadeite-water. These isotopic substitution effects can be ascribed to replacement of SiOM bonds (M is a divalent metal cation in octahedral coordination) by higher frequency SiOAl bonds. The fractionations determined in this study can be combined with quartz- and feldspar-water data of Matsuhisa et al. (1979) and revised magnetite-water data of O'NEIL (1963), to provide a coherent set of mineral-pair fractionations satisfactorily represented by straight lines through the origin on a conventional graph of In /ga versus T^?2. Mineral-water data, on the other hand, cannot readily be fitted to the simple relationship suggested by Bottinga and Javoy (1973). Coefficients “A” for the mineral-pair fractionations 1000 ln α = A × 10⁶T^?2 are:

	No.	Ni (%)	Ga (μg/g)	Ge (μg/g)	Au (μg/g)	Fa (mole %)
Main group	19	7.8–11.7	16–26	29–65	1.7–3.0	11–13
Eagle Station trio	3	14–16	4.5–6	75–120	0.8–1.0	19–20

     

8.

High precision intercalibration of 40Ar-39Ar standards     

J.C Roddick 《Geochimica et cosmochimica acta》1983,47(5):887-898

Intercalibration of one intralaboratory and three interlaboratory standards used in ⁴⁰Ar-³⁹Ar dating has been carried out. In order to provide homogeneous values for ${}^{40}\text{Ar}{}^1{}^{40}\text{K}$ the standards were prepared by careful handpicking. To control the neutron fluence in the Herald Reactor (A.W.R.E.) 16 aliquots of the standards were arranged along 0.6 × 60 cm of a single silica tube. The corrections for all known interferences from K, Ca, Cl were carefully assessed. Two of the hornblende standards, Hb3gr and MMHb-1 appear homogeneous at the 0.1% level while the other two standards, LP-6 and FY12a are not completely homogeneous. The mean values of ${}^{40}\text{Ar}{}^1{}^{40}\text{K}$ when referenced to the previously determined value for Hb3gr (turner et al., 1971) are:

	Ab	Jd	An	Di	Wo	Mt
Q	0.50	1.09	1.59	2.08	2.20	6.11
Ab		0.59	1.09	1.58	1.70	5.61
Jd			0.50	0.99	1.11	5.02
An				0.49	0.61	4.52
Di					0.12	4.03
Wo						3.91

     

9.

Ressources minérales du Tchad: une revue     

Imrich Kusnir  Hamit A. Moutaye 《Journal of African Earth Sciences》1997,24(4):549-562

Chad has an area of about 1.2 million km², is located in the centreof the African continent and is not well explored. Results of importance to the local economic geology have been acquired recently, mainly during mineral exploration:

Hb3gr	hbld	$\text{.08504 ± .05\%}$(±lσ)	1072. m.y.
MMHb-1	hbld	$\text{.03493 ± 05\%}$	518.9 m.y.
LP-6	biot	$\text{.007735 ± .13\%}$	128.5 m.y.
FY12a	hbld	$\text{.02858 ± .25\%}$	435.0 m.y.

1. 

i) all geological formations within Chad territory were reworked/influenced by the Pan-African Orogeny (by the end of the Proterozoic) terminating the crustal evolution of the area with most of the Chad granitoids being formed during this event;

2. 

ii) The Precambrian formations are of Proterozoic age and contain volcanosedimentary series with considerable mineral potential (Au,…);

3. 

iii) the vast Chad Basin (extending into neighbouring countries) has a complex structure and includes several sub-basins and troughs, whose development started during the break-up of Gondwana; they have been filled by up to 10, 000 m of sediments and petroleum and gas occur within these structures;

4. 

iv) well preserved fossil remnants of an Australopithecus have been recently found in Chad; and

5. 

v) large reserves of oil and vaste resources of a variety of minerals (Au, ornamental stones, marbles, diatomites, etc.) have been found.

     

Crustal development in the Agnew region,Western Australia,as shown by Rb/Sr isotopic and geochemical studies

Rb/Sr geochronology on a folded greenstone-granitoid complex in the Agnew area, Western Australia, yields four distinct ages of igneous activity that conform with stratigraphic and intrusive relationships. They are (using $\text{λ}{}^{87}\text{Rb}\text{= 1.42 · 10}{}^{\mathrm{?11}}\text{a}{}^{\mathrm{?1}}$, NBS 70A = 522 ppm Rb and 65.3 ppm Sr):

Pallasites—metal composition,classification and relationships with iron meteorites

Concentrations of Au, As, Co, Ga, Ge, Ir, Ni and W were determined in the metal of 28 different pallasites plus 6 which are probably paired, to help elucidate their origin. Most divide into two clusters:

Oxygen isotope fractionations involving pyroxenes: The calibration of mineral-pair geothermometers

Oxygen isotope fractionations between wollastonite, diopside, jadeite, hedenbergite and water have been experimentally studied at high pressures (1<- PH₂O ≥ 24 kbar) and temperatures (400/dg ≤ T <- 800/dgC) using the three-isotope method (Matsuhisa et al., 1978). Initial ${}^{18}\text{O}{}^{16}\text{O}$ fractionations were made close to equilibrium and initial ${}^{17}\text{O}{}^{16}\text{O}$ ratios were well removed from equilibrium, allowing accurate determinations of the equilibrium ${}^{18}\text{O}{}^{16}\text{O}$ fractionations and of the extent of isotopic exchange. Scanning electron microscope and rate studies show that the wollastonite-water and diopside-water exchange reactions occur largely by solution-precipitation (Ostwald Ripening) mechanisms. Equilibrium ${}^{18}\text{O}{}^{16}\text{O}$ fractionations between water and the minerals wollastonite, diopside, and hedenbergite are in close agreement with one another, whereas significantly more positive fractionations are found for jadeite-water. These isotopic substitution effects can be ascribed to replacement of SiOM bonds (M is a divalent metal cation in octahedral coordination) by higher frequency SiOAl bonds. The fractionations determined in this study can be combined with quartz- and feldspar-water data of Matsuhisa et al. (1979) and revised magnetite-water data of O'NEIL (1963), to provide a coherent set of mineral-pair fractionations satisfactorily represented by straight lines through the origin on a conventional graph of In /ga versus T^?2. Mineral-water data, on the other hand, cannot readily be fitted to the simple relationship suggested by Bottinga and Javoy (1973). Coefficients “A” for the mineral-pair fractionations 1000 ln α = A × 10⁶T^?2 are:

High precision intercalibration of 40Ar-39Ar standards

Intercalibration of one intralaboratory and three interlaboratory standards used in ⁴⁰Ar-³⁹Ar dating has been carried out. In order to provide homogeneous values for ${}^{40}\text{Ar}{}^1{}^{40}\text{K}$ the standards were prepared by careful handpicking. To control the neutron fluence in the Herald Reactor (A.W.R.E.) 16 aliquots of the standards were arranged along 0.6 × 60 cm of a single silica tube. The corrections for all known interferences from K, Ca, Cl were carefully assessed. Two of the hornblende standards, Hb3gr and MMHb-1 appear homogeneous at the 0.1% level while the other two standards, LP-6 and FY12a are not completely homogeneous. The mean values of ${}^{40}\text{Ar}{}^1{}^{40}\text{K}$ when referenced to the previously determined value for Hb3gr (turner et al., 1971) are:

Ressources minérales du Tchad: une revue

Chad has an area of about 1.2 million km², is located in the centreof the African continent and is not well explored. Results of importance to the local economic geology have been acquired recently, mainly during mineral exploration:

Rare earth element diffusion in a natural pyrope single crystal at 2.8 GPa

Volume diffusion rates of Ce, Sm, Dy, and Yb have been measured in a natural pyrope-rich garnet single crystal (Py₇₁Alm₁₆Gr₁₃) at a pressure of 2.8 GPa and temperatures of 1,200-1,450 °C. Pieces of a single gem-quality pyrope megacryst were polished, coated with a thin layer of polycrystalline REE oxide, then annealed in a piston cylinder device for times between 2.6 and 90 h. Diffusion profiles in the annealed samples were measured by SIMS depth profiling. The dependence of diffusion rates on temperature can be described by the following Arrhenius equations (diffusion coefficients in m²/s): % MathType!MTEF!2!1!+- % feaaeaart1ev0aaatCvAUfKttLearuavTnhis1MBaeXatLxBI9gBam % XvP5wqSXMqHnxAJn0BKvguHDwzZbqegm0B1jxALjhiov2DaeHbuLwB % Lnhiov2DGi1BTfMBaebbfv3ySLgzGueE0jxyaibaieYlf9irVeeu0d % Xdh9vqqj-hEeeu0xXdbba9frFj0-OqFfea0dXdd9vqaq-JfrVkFHe9 % pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr0-vqpWqaaeaabiGaciaaca % qabeaadaabauaaaOqaauaabeqaeeaaaaqaaiGbcYgaSjabc+gaVjab % cEgaNnaaBaaaleaacqaIXaqmcqaIWaamaeqaaOGaemiraq0aaSbaaS % qaaiabbMfazjabbkgaIbqabaGccqGH9aqpcqGGOaakcqGHsislcqaI % 3aWncqGGUaGlcqaI3aWncqaIZaWmcqGHXcqScqaIWaamcqGGUaGlcq % aI5aqocqaI3aWncqGGPaqkcqGHsisldaqadaqaaiabiodaZiabisda % 0iabiodaZiabgglaXkabiodaZiabicdaWiaaysW7cqqGRbWAcqqGkb % GscaaMe8UaeeyBa0Maee4Ba8MaeeiBaW2aaWbaaSqabeaacqqGTaql % cqqGXaqmaaGccqGGVaWlcqaIYaGmcqGGUaGlcqaIZaWmcqaIWaamcq % aIZaWmcqWGsbGucqWGubavaiaawIcacaGLPaaaaeaacyGGSbaBcqGG % VbWBcqGGNbWzdaWgaaWcbaGaeGymaeJaeGimaadabeaakiabdseaen % aaBaaaleaacqqGebarcqqG5bqEaeqaaOGaeyypa0JaeiikaGIaeyOe % I0IaeGyoaKJaeiOla4IaeGimaaJaeGinaqJaeyySaeRaeGimaaJaei % Ola4IaeGyoaKJaeG4naCJaeiykaKIaeyOeI0YaaeWaaeaacqaIZaWm % cqaIWaamcqaIYaGmcqGHXcqScqaIZaWmcqaIWaamcaaMe8Uaee4AaS % MaeeOsaOKaaGjbVlabb2gaTjabb+gaVjabbYgaSnaaCaaaleqabaGa % eeyla0IaeeymaedaaOGaei4la8IaeGOmaiJaeiOla4IaeG4mamJaeG % imaaJaeG4mamJaemOuaiLaemivaqfacaGLOaGaayzkaaaabaGagiiB % aWMaei4Ba8Maei4zaC2aaSbaaSqaaiabigdaXiabicdaWaqabaGccq % WGebardaWgaaWcbaGaee4uamLaeeyBa0gabeaakiabg2da9iabcIca % OiabgkHiTiabiMda5iabc6caUiabikdaYiabigdaXiabgglaXkabic % daWiabc6caUiabiMda5iabiEda3iabcMcaPiabgkHiTmaabmaabaGa % eG4mamJaeGimaaJaeGimaaJaeyySaeRaeG4mamJaeGimaaJaaGjbVl % abbUgaRjabbQeakjaaysW7cqqGTbqBcqqGVbWBcqqGSbaBdaahaaWc % beqaaiabb2caTiabbgdaXaaakiabc+caViabikdaYiabc6caUiabio % daZiabicdaWiabiodaZiabdkfasjabdsfaubGaayjkaiaawMcaaaqa % aiGbcYgaSjabc+gaVjabcEgaNnaaBaaaleaacqaIXaqmcqaIWaamae % qaaOGaemiraq0aaSbaaSqaaiabboeadjabbwgaLbqabaGccqGH9aqp % cqGGOaakcqGHsislcqaI5aqocqGGUaGlcqaI3aWncqaI0aancqGHXc % qScqaIYaGmcqGGUaGlcqaI4aaocqaI0aancqGGPaqkcqGHsisldaqa % daqaaiabikdaYiabiIda4iabisda0iabgglaXkabiMda5iabigdaXi % aaysW7cqqGRbWAcqqGkbGscaaMe8UaeeyBa0Maee4Ba8MaeeiBaW2a % aWbaaSqabeaacqqGTaqlcqqGXaqmaaGccqGGVaWlcqaIYaGmcqGGUa % GlcqaIZaWmcqaIWaamcqaIZaWmcqWGsbGucqWGubavaiaawIcacaGL % Paaaaaaaaa!0C76!

Oxygen isotope fractionation between zoisite and water

Oxygen isotope fractionations between zoisite and water have been studied at 400–700°C, PH₂O = 13.4 kbar, using the three-isotope method described by Matsuhisaet al. (1978) and Matthewset al. (1983a). The zoisite-waier exchange reaction takes place extremely slowly and consequently direct-exchange calibration of equilibrium ${}^{18}\text{O}{}^{16}\text{O}$ fractionation factors was possible only at 600 and 700°C. Fractionation factors at 400–600°C were determined from samples hydrothermally crystallized from a glass of the anhydrous zoisite composition. At 600°C, both exchange procedures gave identical fractionations within experimental error. Scanning electron microscope studies showed that the zoisite-water exchange reaction occurs largely by solution-precipitation mass-transfer mechanisms. The slow kinetics of zoisite-water exchange may be typical of hydrous silicates, since additional experiments on tremolite-water and chlorite-water exchange also showed very low rates. When the zoisite-water fractionation factors determined in this study are combined with the quartz and albite-water data of Matsuhisaet al. (1979) and the calcite-water data of O'Nellet al. (1969), mineral-pair fractionations are obtained for which the coefficients “A” in the equation 1000 In α = A × 10⁶T^?2 are:

     

12.

Rb-Sr ages of the Archean rocks from the Vermilion district,northeastern Minnesota     

V Rama Murthy 《Geochimica et cosmochimica acta》1975,39(12):1679-1689

The Vermilion district of northerneastern Minnesota is a classic example of a lower Precambrian greenstone-granite terrane. It is a complex volcanic-sedimentary pile, characterized by repeated periods of volcanism and the presence of intercalated pyroclastic, volcanoclastic and epiclastic rocks. The volcanic-sedimentary pile is surrounded and intruded by contemporaneous granitic batholiths. Several rock units from the district have been dated by the whole-rock Rb-Sr method. The isochron ages and the corresponding initial Sr⁸⁷/Sr⁸⁶ ratios (= I) are:

	Ab	Cc	Zo
Q	0.50	0.50	1.56
Ab		0.00	1.06
Cc			1.06

     

13.

Paleomagnetism and the alpine tectonics of Eurasia V: The paleomagnetism of some mesozoic and cenozoic volcanic rocks from the lebanon     

C.B Gregor  S Mertzman  A.E.M Nairn  J Negendank 《Tectonophysics》1974,21(4):375-395

A sampling of Mesozoic and Tertiary basalts in Lebanon yielded the following information:

	$\text{t(}\text{in b.y.}\text{) ± 2σ}$	$\text{1 ± 2σ}$
Ely Greenstone	$\text{2.69 ± 0.08}$	$\text{0.70056 ± 0.00026}$
Newton Lake Formation	$\text{2.65 ±0.11}$	$\text{0.70086 ± 0.00024}$
Granitic pebbles	$\text{2.69 ± 0.28}$	$\text{0.70078 ± 0.00058}$

Age	D	I	α95	Pole position	dp	dm
Upper Jurassic	95	+21	10.6	114E 2N	5.9	11.2
				66W 2S
Lower Cretaceous	122	+2	9.0	105E 25S	4.5	9.0
				75W 25N
Upper Pliocene	2	+46	7.7	169E 88N	6.3	9.8
				11W 88S

Full-size table

Rb-Sr ages of the Archean rocks from the Vermilion district,northeastern Minnesota

The Vermilion district of northerneastern Minnesota is a classic example of a lower Precambrian greenstone-granite terrane. It is a complex volcanic-sedimentary pile, characterized by repeated periods of volcanism and the presence of intercalated pyroclastic, volcanoclastic and epiclastic rocks. The volcanic-sedimentary pile is surrounded and intruded by contemporaneous granitic batholiths. Several rock units from the district have been dated by the whole-rock Rb-Sr method. The isochron ages and the corresponding initial Sr⁸⁷/Sr⁸⁶ ratios (= I) are:

Paleomagnetism and the alpine tectonics of Eurasia V: The paleomagnetism of some mesozoic and cenozoic volcanic rocks from the lebanon

A sampling of Mesozoic and Tertiary basalts in Lebanon yielded the following information:

Chemical classification of iron meteorites—VIII. Groups IC. IIE,IIIF and 97 other irons

Concentrations of Ni, Ga, Ge and Ir in 106 iron meteorites are reported. Three new groups are defined: IC, IIE and IIIF containing 10, 12 and 5 members, respectively, raising the number of independent groups to 12. Group IC is a cohenite-rich group distantly related to IA. Group IIE consists of those irons previously designated Weekeroo Station type and five others having similar compositions though diverse structures. The IIE irons are compositionally similar to the mesosiderites and pallasites, and the three groups probably formed at similar heliocentric distances. The mixing of the globular IIE silicates with the metal probably occurred during shock events. Group IIIF is a well-defined group of low-Ni and low-Ge irons. The compositions of these groups are summarized as follows:

     

15.

Petroleum engeneering: A. Mayer-gürr. (Geology of petroleum, 3. H. Beck-mann, editor) Enake, Stuttgart, 1976, 208 pp., DM 16.80     

D.L. Katz 《Tectonophysics》1977,43(3-4)

     

16.

Studies in diffusion—III. Oxygen in feldspars: an ion microprobe determination     

B.J Giletti  M.P Semet  R.A Yund 《Geochimica et cosmochimica acta》1978,42(1):45-57

Self-diffusion of oxygen in adularia, anorthite, albite, oligoclase and labradorite has been measured by isotope exchange of oxygen between natural feldspars and hydrothermal water enriched in ¹⁸O. The analysis consisted of measuring the ¹⁸O/¹⁶O gradient inward from the feldspar surface using an ion microprobe, and fitting a solution of the diffusion equation to the data. Depth of the sputtered hole was measured with an optical interferometer. Linear Arrhenius plots were obtained:

Group	Ni (%)	Ga (ppm)	Ge (ppm)	Ir (ppm)
IC	6.1–6.8	42–54	85–250	0.07–10
IIE	7.5–9.7	21–28	62–75	0.5–8
IIIF	6.8–7.8	6.3–7.2	0.7–1.1	1.3–7.9

     

17.

Earthquake recurrence on the Calaveras fault east of San Jose, California     

Charles G. Bufe  Philip W. Harsh  Robert O. Burford 《Tectonophysics》1979,52(1-4)

Occurrence of small (3 M_L < 4) earthquakes on two 10-km segments of the Calaveras fault between Calaveras and Anderson reservoirs follows a simple linear pattern of elastic strain accumulation and release. The centers of these independent patches of earthquake activity are 20 km apart. Each region is characterized by a constant rate of seismic slip as computed from earthquake magnitudes, and is assumed to be an isolated locked patch on a creeping fault surface. By calculating seismic slip rates and the amount of seismic slip since the time of the last significant (M 3) earthquake, it is possible to estimate the most likely date of the next (M - 3) event on each patch. The larger the last significant event, the longer the time until the next one. The recurrence time also appears to be increased according to the moment of smaller (2 < M_L < 3) events in the interim. The anticipated times of future larger events on each patch, on the basis of preliminary location data through May 1977 and estimates of interim activity, are tabulated below with standard errors. The occurrence time for the southern zone is based on eight recurrent events since 1969, the northern zone on only three. The 95% confidence limits can be estimated as twice the standard error of the projected least-squares line. Events of M 3 should not occur in the specified zones at times outside these limits. The central region between the two zones was the locus of two events (M = 3.6, 3.3) on July 3, 1977. These events occurred prior to a window based on the three point, post-1969 slip-time line for the central region.

	$\text{d}{}_0\text{(}\text{cm}{}^2\text{/sec}\text{)}$	$\text{Q (}\text{kcal/g-atom O}\text{)}$	$\text{T(°C)}$
Adularia (Or98)	$\text{4.51 × 10}{}^{\mathrm{?8}}$	25.6	350–700
Albite (Ab97, Ab99)	$\text{2.31 × 10}{}^{\mathrm{?9}}$	21.3	350–800
Anorthite (An96)	$\text{1.39 × 10}{}^{\mathrm{?7}}$	26.2	350–800

Latitude	Longitude	Depth	Mag.	Target date	Standard error (days)
37°17′± 2′N	121°39′±2′W	5.0 ±2 km	3.0–4.0	7-22-77	22.3
37°26′± 2′N	121°47′±2′W	6.0 ± 2 km	3.0–4.0	9-02-77	8.0

Full-size table

Studies in diffusion—III. Oxygen in feldspars: an ion microprobe determination

Self-diffusion of oxygen in adularia, anorthite, albite, oligoclase and labradorite has been measured by isotope exchange of oxygen between natural feldspars and hydrothermal water enriched in ¹⁸O. The analysis consisted of measuring the ¹⁸O/¹⁶O gradient inward from the feldspar surface using an ion microprobe, and fitting a solution of the diffusion equation to the data. Depth of the sputtered hole was measured with an optical interferometer. Linear Arrhenius plots were obtained:

Earthquake recurrence on the Calaveras fault east of San Jose, California

Occurrence of small (3 M_L < 4) earthquakes on two 10-km segments of the Calaveras fault between Calaveras and Anderson reservoirs follows a simple linear pattern of elastic strain accumulation and release. The centers of these independent patches of earthquake activity are 20 km apart. Each region is characterized by a constant rate of seismic slip as computed from earthquake magnitudes, and is assumed to be an isolated locked patch on a creeping fault surface. By calculating seismic slip rates and the amount of seismic slip since the time of the last significant (M 3) earthquake, it is possible to estimate the most likely date of the next (M - 3) event on each patch. The larger the last significant event, the longer the time until the next one. The recurrence time also appears to be increased according to the moment of smaller (2 < M_L < 3) events in the interim. The anticipated times of future larger events on each patch, on the basis of preliminary location data through May 1977 and estimates of interim activity, are tabulated below with standard errors. The occurrence time for the southern zone is based on eight recurrent events since 1969, the northern zone on only three. The 95% confidence limits can be estimated as twice the standard error of the projected least-squares line. Events of M 3 should not occur in the specified zones at times outside these limits. The central region between the two zones was the locus of two events (M = 3.6, 3.3) on July 3, 1977. These events occurred prior to a window based on the three point, post-1969 slip-time line for the central region.

Seleniferous minerals of palladium and platinum from ouro preto-bearing mineralisation in Brazil

Foram determinadas as composições químicas e as idades Rb–Sr de mica branca, feldspato potássico e de rochas totais das mineralizações de esmeraldas de Capoeirana e Belmont, de pegmatitos sem esmeraldas e dos gnaisses Borrachudos, Monlevade e Guanhães da região de Nova Era–Itabira–Ferros (Minas Gerais, Brazil). Os gnaisses graníticos Borrachudos, os gnaisses bandados Monlevade, seus respectivos pegmatitos e veios/schlieren pegmatóides, e os gnaisses Guanhães, adquiriram suas texturas e composições mineralógicas atuais há cerca de 1.9 Ga no contexto do evento Transamazônico.As rochas regionais encaixantes típicas das ocorrências de esmeraldas são os gnaisses Monlevade que pertencem a uma sequência metavulcano-sedimentar de tipo greenstone belt. O evento principal de formação de esmeraldas em Belmont e Capoeirana foi uma reação metassomática dos pegmatitos anatéticos ricos em Be com rochas ultrabásicas ricas em Cr durante o evento Transamazônico em torno de 1.9 Ga. Em Capoeirana nesse contexto os pegmatitos com feldspato potássico ricos em Be foram transformados em rochas de plagioclasio–quartzo. As idades Rb–Sr de cerca de 480 Ma de minerais das mineralizações de esmeralda resultaram da reequilibração de biotitas e feldspatos Transamazônicos durante o evento Brasiliano.Os pegmatitos não-metamórficos e sem esmeralda da região estudada foram formados no evento Brasiliano há 477±14 Ma. O grau de diferenciação dos pegmatitos, estudado em diagramas indicadores específicos como por exemplo Cs vs. K/Rb de micas brancas e feldspatos potássicos, varia desde pegmatitos cerámicos até muscovita-pegmatitos, à pegmatitos de metais raros e até berilíferos. Alguns dos pegmatitos apresentam marcante diferenciação interna.

Determination of uranium and thorium in meteorites by the delayed neutron method

Delayed neutron measurements of U and Th in three meteorites yield the following values:

     

20.

The chemical classification of iron meteorites—VII. A reinvestigation of irons with Ge concentrations between 25 and 80 ppm     

Edward R.D Scott  John T Wasson  V.F Buchwald 《Geochimica et cosmochimica acta》1973,37(8):1957-1983

We report Ni, Ga, Ge and Ir concentrations for 193 irons. The compositional trends in groups IIIA and IIIB are redefined, and the suggestion by Wasson and Kimberlin that they represent a single fractionation sequence (group IIIAB) is confirmed. A new group, HIE, is similar in its properties to group IIIA but distinguished by lower Ga/Ni and Ge/Ni ratios, larger bandwidths and the formation of haxonite (Fe, Ni)₂₃C₆ in each of its members. A sixth member, Hassi-Jekna, has been added to group IIIC, extending its Ge range up to 70 ppm. The characteristics of these groups can be summarized as follows:

Bruderheim	U (ppb)	Th(ppb)
Bruderheim	$\text{14.5 ± 1.0}$	$\text{171 ± 65}$
Peace River	$\text{11.8 ± 0.7}$	$\text{96 ± 46}$
Stannern	$\text{220 ± 6}$	$\text{563 ± 190}$

     

Group	Structure	Ni%	Ga(ppm)	Ge(ppm)	Ir(ppm)
IIIA	Om	7.1–9.3	7–23	32–47	0.17–19
IIIB	Om	8.4–10.5	16–21	27–46	0.014–0.17
IIIC	Off-Of	10.5–13.0	11–27	8.6–70	0.08–0.6
IIIE	Og	8.2–8.9	17–19	34–37	0.05–0.6 The Ge-Ni correlation is positive in IIIA, negative in IIIB and IIIC, and there is no significant correlation in IIIE. San Cristobal is identified as a member of group IAB, thereby extending the Ge and Ni range of this group to 25 ppm and 25 per cent, respectively. Previous reports of wide cooling-rate variations in group IIIAB are not substantiated, and current evidence favors a core over a raisin-bread model for this group. There appears to be no genetic relationship between group IIIAB and either the pallasites or the mesosiderites

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号

The chemical classification of iron meteorites—VII. A reinvestigation of irons with Ge concentrations between 25 and 80 ppm

We report Ni, Ga, Ge and Ir concentrations for 193 irons. The compositional trends in groups IIIA and IIIB are redefined, and the suggestion by Wasson and Kimberlin that they represent a single fractionation sequence (group IIIAB) is confirmed. A new group, HIE, is similar in its properties to group IIIA but distinguished by lower Ga/Ni and Ge/Ni ratios, larger bandwidths and the formation of haxonite (Fe, Ni)₂₃C₆ in each of its members. A sixth member, Hassi-Jekna, has been added to group IIIC, extending its Ge range up to 70 ppm. The characteristics of these groups can be summarized as follows: