ISSN:0016-786X    

DOI:10.1080/11035898609453749

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898609453750

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Radiometric dating of the serorogenic Svecokarelian Enkullen and Fjällberg granites, south central Sweden, yield two parallel Rb-Sr whole-rock isochron ages of 1755 ± 17 Ma and 1758 ± 14 Ma, respectively. The initial87Sr/86Sr ratios arc also similar; 0.7063 + 0.0056 and 0.7065 ± 0.0034, respectively. A U-Pb dating of zircons from the Fjällberg granite also gives a corrsponding age, i.e., an upper intercept with concordia of 1748+74-45Ma. A recalculation of the zircons with the U-Pb model of Wickman (1983) yields an age of 1765 Ma. The agreement between the Rb-Sr and U-Pb datings strongly indicates that they represent true primary crystallizing ages.

ISSN:0016-786X    

DOI:10.1080/11035898609453751

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898609453752

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Three granitoid suites from near Linköping, SE Sweden, belong to a major belt of mid-Proterozoic (post-Svecokarelian) magmatic rocks which displays Andinotype geological characteristics. The suites have sub-alkaline major element geochemistry and ‘within plate’ trace element (high Y, Nb) characteristics. Meta-aluminous chemistry and low Ga contents suggest dominantly igneous sources. Assuming an intrusion age of around 1.7 Ga, Sm-Nd isotope systematics indicate an average crustal residence period of about 0.2 Ga. One interpretation of these data is that these suites have developed in an Andinotype environment, not necessarily as subduction generated marginal suites but possibly in an ensialic rift environment on the continental side of a hypothetical calc-alkaline belt. An alternative interpretation is that the ‘within-plate’ trace element characteristics are inherited from a Proterozoic crustal precursor.

ISSN:0016-786X    

DOI:10.1080/11035898609453753

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898609453754

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The Holtäkt conglomerate has been found in a glacial drift 9 km north of Falun. It is a conglomerate or sedimentary breccia with cpiclastic and/or pyroclastic matrices. The pebbles, often angular, are of gncissic granite, primorogenic diorite and gabbro, various metavolcanics (leptite formation) and mctascdiments. The matrix is a quartz sandstone, or a basaltic tuff. K-Ar age determination of the tuff has yielded 1504 ± 18 Ma, indicating that the Holtäkt conglomerate has to be referred to the Digerbcrg formation of central Dalccarlia.

ISSN:0016-786X    

DOI:10.1080/11035898609453755

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue

ISSN:0016-786X    

DOI:10.1080/11035898609453738

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor