摘要:

A preliminary investigation of carbon and oxygen isotopes in ore-associated carbonates from Bergslagen, south-central Sweden, reveals a large spread in isotopic composition: δ13C ranges from - 7 to + 65%, and δ18O between + 4 and + 26% (rel. SMOW). However, each locality seems to be characterized by a unique isotopic composition. It is suggested that the isotopic composition of the carbonates originally had a uniform marine signature, and that the present variability in isotopic composition is due to secondary alteration effects. The extent of alteration, and consequently the observed isotopic compostion of the carbonates, is a function of the ore-forming activity and the post-depositional history of each district and it is thus suggested that carbon and oxygen isotope studies may be useful tools for sulphide ore prospecting.

ISSN:0016-786X    

DOI:10.1080/11035898609453049

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898609453050

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

A study of major element and Rb, Sr geochemistry as well as clay mineralogy in argillites from the dolerite-intruded, Late Proterozoic fluviatile Almesåkra group of Sweden is reported. The contents and proportions of the alkalis in the potassic, mainly non-calcareous argillites are determined largely by the composition of the associated feldspathic sandstones. The basic intrusions influenced the oxidation level in the red argillites with reduction of hematite in greyish to blackish contact rocks. In red argillites, least influenced by the intrusions, the clay mineralogy is virtually illitic and the illite crystallinity indicates a deep-diagenetic to diagenetic degree of metamorphism. Chlorites, like illite crystallinity, are best developed in argillites closest to the intrusions. The Sr-level in contact argillites is much higher than in other Precambrian shales. It is significantly lower in the red argillites. The difference in Sr-contents is suggested to be due mainly to a transfer of Sr from the melts which were comparatively high in this element.

ISSN:0016-786X    

DOI:10.1080/11035898609453051

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898609453052

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

An occurrence of apatite-rich rocks of carbonatitic affinity at Främlingshem, SW of Gävle, central Sweden, is reported. Boulders and cobbles of two lithologically related types (dominated by apatite-calcite and chlorite-apatite, respectively) have been found. Major constituents are fluorapatite with a87Sr/86Sr ratio of 0.7027, Sr-rich calcite (2600 ppm) with (δ13C = -3.9 ± 0.2% vs PDB and δ18O = 14.9 ± 0.5% vs SMOW, chlorite completely replacing biotite or phlogopite, and fragments of granitoids and other rocks. The apatite-rich rocks were apparently emplaced as a ‘crystal-mush’, at a low temperature. They are post-Svecokarelian in age, probably formed between 1750 Ma and 1100 Ma ago, a timespan comprising two or more periods of tensional movements in central Sweden. The location of the Främlingshem rocks near a graben structure is consistent with their carbonatitic affinity.

ISSN:0016-786X    

DOI:10.1080/11035898609453053

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Aston, S. R. (ed.), 1983:Silicon geochemistry and biogeochemistry.248 sidor, 79 figurer, 41 tabeller. Academic press, London. ISBN 0-12-065620-5. Pris GBP 23,50. Reviewed by Ulf Sturesson

ISSN:0016-786X    

DOI:10.1080/11035898609453054

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Radiometric dating of the reddish grey, medium- to coarse-grained Karlshamn granite, south Sweden, yields an intrusive age of c. 1400 Ma. During later activity and block movements rest solutions from the crystallizing magma intruded along fault zones, giving rise to small bodies of leucogranite. Activity in the Protogine zone and intrusion of finegrained granitic dikes in the Vånga granite 1250–1200 Ma ago further lowered the K-Ar biotite ages in the Karlshamn and leucogranites.

ISSN:0016-786X    

DOI:10.1080/11035898609453055

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Results of gravity and aeromagnetic measurements have been used for studying the subsurface shape of the Fellingsbro-Blixterboda granite massif, which was formed during the late stages of the Svecofennian orogeny, approximately 1800 Ma ago. The large negative gravity anomaly (ca. -120 gu) over the massif is interpreted to be caused by the relatively low density of the granite itself. The shape and size of the anomaly indicate that the exposed granite is thickest at its southern margin, reaching a depth of at least 15 km and possibly 20 km. To the north a considerable drop occurs in the gravity anomaly, suggesting a laccolithic form for the central and northern part of the granite massif. A main feature of the aeromagnetic anomalies over the Fellingsbro-Blixterboda granite is that they are conspicuously higher over the laccolithic part of the granite than over the intrusive, deep-going, stock-shaped granite, indicating a low magnetization of the latter part. Results of susceptibility determinations support this assumption. The origin and emplacement of the Fellingsbro-Blixterboda granite is apparently closely connected with the late orogeny of south central Sweden. The general shape of this granite massif is consistent with a mechanism of diapiric emplacement and a flow favoured by a zone of weakness in the Svecofennian basement.

ISSN:0016-786X    

DOI:10.1080/11035898609453056

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898609453057

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Stouge, S. S., 1984: Conodonts of the Middle Ordovician Table Head Formation, western Newfoundland.Fossils and Strata 16, 1–145; Pls. 1–18. Universitetsforlaget, Oslo. ISBN 82-0009548-7. Price NKR 180.00, USD 30.00. Reviewed by Maurits Lindström

ISSN:0016-786X    

DOI:10.1080/11035898609453058

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor