全文获取类型
收费全文 | 51篇 |
免费 | 2篇 |
专业分类
大气科学 | 3篇 |
地球物理 | 3篇 |
地质学 | 33篇 |
海洋学 | 2篇 |
天文学 | 3篇 |
自然地理 | 9篇 |
出版年
2015年 | 1篇 |
2014年 | 1篇 |
2013年 | 1篇 |
2011年 | 2篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 2篇 |
2004年 | 3篇 |
2002年 | 1篇 |
2000年 | 4篇 |
1997年 | 2篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1967年 | 2篇 |
1964年 | 1篇 |
排序方式: 共有53条查询结果,搜索用时 62 毫秒
51.
Oxygen and Hydrogen Isotope Stratigraphy of the Rustenburg Layered Suite, Bushveld Complex: Constraints on Crustal Contamination 总被引:5,自引:1,他引:4
HARRIS CHRIS; PRONOST JULIE J. M.; ASHWAL LEWIS D.; CAWTHORN R. GRANT 《Journal of Petrology》2005,46(3):579-601
New 18O values for plagioclase, pyroxene and olivine, and limitedwhole-rock D values are presented for samples from the RustenburgLayered Suite of the Bushveld Complex, South Africa. In combinationwith existing data, these provide a much more complete compositeO-isotope stratigraphy for the intrusion. Throughout the layeredsuite, mineral 18O values indicate that the magmas from whichthey crystallized had 18O values that were about 7·1,that is, 1·4 higher than expected for mantle-derivedmagmas, suggesting extensive crustal contamination. More limitedH-isotope data suggest that the OH present within whole rocks,regardless of the degree of alteration, is of magmatic originand not an alteration phenomenon. There appears to be no systematicchange in 18O value with stratigraphic height and this requiresthe contamination to have taken place in a staging chamberbefore emplacement of the magma(s) into the present chamber.Large amounts (3040%) of contamination by the lower tomiddle crust are needed to explain these 18O values, which isin general agreement with previous estimates based on Sr- andNd-isotope data. Alternatively, smaller amounts of contamination(20%) by sedimentary rocks, or their partial melts, representedby the country rock can explain the data, but it is not apparenthow such material could have been present at the depth of thestaging chamber in the lower to middle crust. KEY WORDS: Bushveld Complex; Rustenburg Layered Suite; oxygen isotopes; hydrogen isotopes; crustal contamination 相似文献
52.
P. H. REYNOLDS N. G. CULSHAW R. A. JAMIESON S. L. GRANT K. J. McKENZIE 《Journal of Metamorphic Geology》1995,13(2):209-221
Abstract 40Ar/39Ar data (on hornblende, muscovite and K-feldspar) are presented for samples from the western Grenville Province taken along a 140-km traverse from the Grenville Front into the Britt domain. Our interpretation is based on 28 new analyses, synthesized with 20 previously reported from the traverse area. In regions where comparisons are possible, muscovite and (large domain) K-feldspar apparent ages appear similar (at c. 920–930 Ma), but throughout the traverse, these are c. 60–70 Myr younger than the hornblende ages. The inferred cooling rate over the c. 350–500°C temperature range, c.2°C Myr-1, is appropriate for exhumation controlled by post-orogenic erosional unroofing. At the Grenville Front Tectonic Zone (GFTZ) — Britt domain boundary there is a c. 25-Myr offset in both hornblende and muscovite/K-feldspar ages. We interpret the lower ages in the Britt domain to reflect variations in crustal thickness and geothermal gradient between the flank and interior of a thick orogen. The argon data from the GFTZ are interpreted in the context of an asymmetric crustal-scale antiformal structure developed during a late episode of convergence. Hornblende from rocks on either side of the core of the antiform has an apparent age of c. 990 Ma, our estimate of the age of the compressional event. In the west, we infer that these date the short-lived thermal event associated with the development of the crustal-scale antiform previously postulated. In the east, the ages reflect the cooling of material brought toward the surface in the flank of the antiform. Hornblendes from the antiform core appear to contain excess radiogenic argon. We suggest that this was the ambient argon in rocks transported from depth that was subsequently trapped when the rocks cooled rapidly. 相似文献
53.