Investigations of an intrusive contact,northwest Nelson,New Zealand—I. Thermal,chronological and isotopic constraints     

T.Mark Harrison  Ian McDougall 《Geochimica et cosmochimica acta》1980,44(12):1985-2003

In the Nelson area of New Zealand, intrusion of the Separation Point Batholith 114 Ma ago caused thermal metamorphism in the adjacent Devonian Rameka Gabbro that allowed radiogenic ⁴⁰Ar to diffuse partially out of hornblendes in the gabbro.Comparison of mineral ages in the batholith (obtained by the K-Ar, ${}^{40}\text{Ar}{}^{39}\text{Ar}$, Rb-Sr, U-Pb and fission track methods) with closure temperature estimates for the various isotopic systems has allowed thermal histories of several samples to be resolved. These curves indicate that, following emplacement, the batholith cooled at an exponentially decreasing rate reaching 100°C by about 75 Ma ago.Oxygen isotope measurements on minerals from the gabbro and granodiorite give calculated equilibrium water compositions of +7 and +9 of δ¹⁸O_SMOW respectively. Measured porosities from samples of the gabbro yield a model permeability of 3 × 10^?17 m¹². These results confirm that heat transfer from the batholith to the gabbro was predominantly by conduction. A numerical heat flow model has been developed for the region, and shows that samples in the gabbro near the contact reached ~600°C. whereas 5 km away from the contact, the samples were only raised ~ 50°C above the ambient temperature.Excess ⁴⁰Ar was identified as causing a significant scatter in the K-Ar ages of hornblendes from the gabbro. Though obscured by this effect, these data suggest a crystallization age of the Rameka Gabbro of 367 Ma, which is consistent with geological evidence.  相似文献   

Paleomagnetism of samples from the axial zone of the Afar depression     

C.G.A. Harrison  L. Stieltjes  E. Tarasiewicz 《Earth and Planetary Science Letters》1977,34(2):273-283

We have studied SmNd systematics in pyroxene and phosphate mineral separates of Angra dos Reis. A pyroxene-phosphate internal isochron age ofT₂ = 4.55 ± 0.04AE is obtained, in excellent agreement with reported Pb-Pb ages.¹⁴²Nd/¹⁴⁴Nd ratios in pyroxene samples are systematically larger than those in phosphates by 6 parts in 10⁵. This variation is tentatively assigned to a radiogenic contribution from extinct¹⁴⁶Sm. Fission xenon components in pyroxene and phosphate separates are characterized by discrete ratios of fission/spallation and evidence is presented for a third ratio in celsian. It is shown that this characteristic is due to a close association of²⁴⁴Pu with the light REE. Computed ratios²⁴⁴Pu/Nd are the same in pyroxene and phosphate separates, but²⁴⁴Pu/²³⁸U and²⁴⁴Pu/²³²Th ratios are not. Taking the fission xenon retention age to be 4.55 AE, we obtain an abundance ratio²⁴⁴Pu/Nd= 1.5 × 10^?4 (or an atomic ratio²⁴⁴Pu/¹⁵⁰Nd= 1.6 × 10^?3) at this time and in the region of the solar system where the Angra dos Reis parent body formed. The exposure age of Angra dos Reis, as obtained by the⁸¹Kr-⁸³Kr method is55.5 ± 1.2m.y. Neutron capture during the 55.5-m.y. exposure to cosmic rays increased the ratio¹⁵⁰Sm/¹⁴⁹Sm in Angra dos Reis by 6 parts in 10⁴.  相似文献   

Evaluating System for Ground-Water Contamination Hazards Due to Gas-Well Drilling on the Glaciated Appalachian Plateau     

Samuel S. Harrison 《Ground water》1983,21(6):689-700

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⁴⁰Ar/³⁹Ar age and thermal history of the Kirin chondrite     

Sungshan Wang  Ian McDougall  Neil Tetley  T. Mark Harrison 《Earth and Planetary Science Letters》1980,49(1):117-131

The Kirin meteorite, a large (2800kg) H5 chondrite, fell in Kirin Province, China in 1976. A sample from each of the two largest fragments (K-1, K-2) yield⁴⁰Ar/³⁹Ar total fusion ages of 3.63 ± 0.02b.y. and 2.78 ± 0.02b.y. respectively.⁴⁰Ar/³⁹Ar age spectra show typical diffusional argon loss profiles. Maximum apparent ages of 4.36 b.y. (K-1) and ～4.0 b.y. (K-2) are interpreted as possible minimum estimates for the age of crystallization of the parent body.The⁴⁰Ar/³⁹Ar ages found for gas released at low temperature are about 2.2 b.y. for K-1 and about 0.5 b.y. for K-2, suggesting that this meteorite may have suffered two discrete collisional events that caused degassing of radiogenic argon. Modelling of possible thermal events in the parent body indicates that samples K-1 and K-2 were at a depth of less than 3 m from the base of an impact melt of a thickness less than 7 m and separated by no more than ～2 m from one another at the time of the heating event about 0.5 b.y. ago. Further, the duration of heating was probably less than a few years.Calculations from³⁸Ar data yield exposure ages for samples K-1 and K-2 of about 5 m.y., similar to that found for many other H chondrites.  相似文献   

Critical sections in the Western Andes of Central Peru     

Dr. J. V. Harrison 《International Journal of Earth Sciences》1960,50(1):630-639

Summary Seven valley-sections across the Pacific slopes of the Andes provide evidence interpreted as follows. Cretaceous and post-Senonian beds were folded, thrust and eroded before an immense pile of lava and ash about 60 miles across was erupted. A granitic batholith about 30 miles wide cut through them and the edge of the folded sediments. Erosion unroofed this batholith and then more lava and ash erupted whilst normal faulting proceeded with down throw towards the Pacific. Uplift of about 12 000 feet in rather recent time is called for to account for high Andean plateau. In brief folding due to compression ended. Vulcanicity, magmatic emplacement, faulting and vertical movement succeeded.

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Zusammenfassung Die Profile in sieben die Westhänge der Anden querenden Tälern lassen folgenden Sachverhalt erkennen. Ablagerungen der Kreidezeit und der Zeit nach dem Senon wurden gefaltet, überschoben und erodiert, ehe die Eruption einer ungeheuren, über 100 km breiten Masse von Lava und Aschen erfolgte. Ein etwa 50 km breiter granitischer Batholith durchdrang die Vulkanite und den Rand der gefalteten Sedimentgesteine. Die Erosion entblößte diesen Batholithen, und dann wurden wiederum Lava und Aschen gefördert, während Abschiebungen, mit Absenkung des pazifischen Flügels, in Tätigkeit traten. Man muß mit Hebungen von etwa 4 km in ziemlich junger Zeit rechnen, um das Andenhochplateau erklären zu können. Kurz gesagt, die Faltung durch Einengung endete. Sie wurde abgelöst von Vulkanismus, Platznahme plutonischer Massen, Bruchtektonik und Vertikalbewegung.

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Sterane distribution of solid bitumen pyrolyzates. Changes with biodegradation of crude oil in the Ouachita Mountains,Oklahoma     

Joseph A Curiale  William E. Harrison  Garmon Smith 《Geochimica et cosmochimica acta》1983,47(3):517-523

Solid bitumens (grahamite and impsonite) of southeastern Oklahoma have been shown to originate from near-surface alteration of crude oil (Curiale, 1981; Curiale and Harrison, 1981). Pyrolysis of these solids has been employed to compare the sterane distribution of geographically proximate oils to that of the bitumens. The ratio of rearranged to regular steranes is higher in the pyrolyzates than in the oils, a finding consistent with a bitumen origin due to biodegradation of oil. The remaining presence of steranes, particularly regular steranes, in the bitumens suggests that sterane occlusion may have occurred prior to or during the alteration process, thus removing tetracyclic compounds from the influence of microbial attack. These data suggest that pyrolysis-$\text{GC}\text{MS}$ offers a viable approach to correlation problems involving solid bitumens.  相似文献   

Dynamics of Blinkers     

Bewsher  D.  Parnell  C.E.  Pike  C.D.  Harrison  R.A. 《Solar physics》2003,215(2):217-237

The relative Doppler and non-thermal velocities of quiet-Sun and active-region blinkers identified in Ov with CDS are calculated. Relative velocities for the corresponding chromospheric plasma below are also determined using the Hei line. Ov blinkers and the chromosphere directly below, have a preference to be more red-shifted than the normal transition region and chromospheric plasma. The ranges of these enhanced velocities, however, are no larger than the typical spread of Doppler velocities in these regions. The anticipated ranges of Doppler velocities of blinkers are 10–15 km s^–1 in the quiet Sun (10–20 km s^–1 in active regions) for Hei and 25–30 km s^–1 in the quiet Sun (20–40 km s^–1 in active regions) for Ov. Blinkers and the chromosphere below also have preferentially larger non-thermal velocities than the typical background chromosphere and transition region. Again the increase in magnitude of these non-thermal velocities is no greater than the typical ranges of non-thermal velocities. The ranges of non-thermal velocities of blinkers in both the quiet Sun and active regions are estimated to be 15–25 km s^–1 in Hei and 30–45 km s^–1 in Ov. There are more blinkers with larger Doppler and non-thermal velocities than would be expected in the whole of the chromosphere and transition region. The recently suggested mechanisms for blinkers are revisited and discussed further in light of the new results.  相似文献   

Stratigraphic control of hot fluids on anthracitization, Lackawanna synclinorium, Pennsylvania     

Michael J. Harrison  Stephen Marshak  Charles M. Onasch 《Tectonophysics》2004,378(1-2):85-103

The Lackawanna synclinorium of Pennsylvania contains abundant coal that was altered to anthracite rank during the Late Paleozoic Alleghanian orogeny. Why did the coal in the synclinorium undergo anthracitization? Two alternatives have been suggested. (1) The region was buried deeply during and/or after the Alleghanian orogeny and thus became hot in response to Earth's geothermal gradient; and (2) hot fluids migrating from the orogen toward the foreland carried heat into the coal and caused anthracitization. If the second hypothesis is correct, the region should contain evidence that hot fluids passed through the coal. Field observations, illite-crystallinity studies and fluid-inclusion analyses indicate that the coal-bearing Pottsville and Llewellyn Formations, and an underlying detachment fault, called the Pottchunk fault (at or slightly below the base of the Pottsville Formation), acted as a regional aquifer for the migration of hot fluids during the Alleghanian orogeny. The presence of quartz veins and the hydrothermal minerals tosudite and pyrophyllite in strata above the Pottchunk fault, and the apparent absence of an illite-crystallinity burial gradient in the underlying strata, suggest that fluids migrated through large pores in coarse-grained sandstones, through abundant fractures that developed in response to Alleghanian deformation, and along the Pottchunk fault. The quartz veins, tosudite and pyrophyllite mineralization do not occur below the Pottchunk fault (except at one locality), suggesting that fluid flow was greater above the fault, perhaps because fracturing accompanying deformation increased permeability of the fault's hanging wall. Fluid inclusions in the Pottsville and Llewellyn Formations indicate fluids achieved a minimum temperature of 270 °C at a depth of 3.1–8.5 km. Heat-flow calculations constrained by fluid-inclusion data show the heat carried by the migrating fluids through the coal-bearing strata was sufficient to elevate the rock temperature to anthracite-grade conditions (250 °C), assuming that the fluid event lasted about 1 year. Thus, deep burial (6–9 km) of the coal-bearing strata in the Lackawanna synclinorium was not required for anthracitization. Anthracitization was likely the result of stratigraphically controlled hot fluid migration through the coal-bearing strata at shallow depths (≤5 km).  相似文献   

Aurora diaries     

Giles Harrison 《Astronomy& Geophysics》2005,46(4):4.31-4.34

Giles Harrison uses the diary of an 18th-century apothecary from Stroud to document appearances of the aurora borealis. From this record and sightings from Europe over the same period, he deduces that aurorae were visible further south some 200 years ago.  相似文献   

Pollen-based reconstruction of vegetation patterns of China in mid-Holocene   总被引：1，自引：0，他引：1  

Ge Yu  Xiangjun Sun  Boqiang Qin  Changqing Song  Haiyu Li  I. C. Prentice  P. S. Harrison 《中国科学D辑(英文版)》1998,41(2):130-136

Biomization provides an important way to assign pollen taxa to biomes and to simulate palaeo-vegetation patterns, so that pollen data can be mapped to reconstruct biogeography and climate. The authors have tested the applicability of this procedure to assign modern pollen surface samples from China to biomes. The procedure successfully delineated the major vegetation types of China. When the same procedure was applied to 6 ka B. P. fossil pollen samples, the reconstructions showed that the forest zones were systematically shifted northwards ca. 300–500 km beyond their present northern limits in eastern China; the area of desert and steppe vegetation was reduced compared to the present in northwestern China; the area of tundra was reduced largely on the Tibetan Plateau. This research is a contribution to the project of BIOME 6000 in Pacific-Asian regions. Project supported by the Funding for Returned Students from the Overseas of the State Education Commission of China, the Postdoctoral Station, and State Pilot Laboratory of Coast & Island Development of Nanjing University, Financial support has also been provided by European Community (EV5V-CT95-0075) and by the Swedish Natural Science Research Council (G-AA/GU 09334-321).  相似文献