摘要:

The silver-rich zinc-lead sulfide deposit of Harmsarvet, 14 km NW of the famous ore deposits of Falun, south central Sweden, is located in a series of Precambrian biotite gneisses, about 2 km SE of a monzonite intrusion. Host rock to the mineralisation has undergone hydrothermal alteration, with especially sericitisation and saussuritisation on a large scale. The silver minerals are native silver, acanthite and silver-antimony-sulfosalts with an important part of the silver present as submicroscopic inclusions in secondary pyrite formed at the expense of pyrrhotite. On average, ore contains 0.39% Ag. A temperature of at least 177°C is proposed for the formation of the major part of the mineralisation.

ISSN:0016-786X    

DOI:10.1080/11035898009450876

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009450877

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Alternating field and thermal demagnetisation studies of lavas and sediments assigned to the Proterozoic Jotnian of western Sweden (Dalarna) and eastern Norway are reported. Hematite is the predominant remanence carrier in the sediments. These locally record a dipolar axis of magnetisation D = 14° and I = 10°, but the bulk of the sediments, including the western part of the outcrop and all of the upper sequence, have a characteristic remanence ca. D = 160°, I = 35°, interpreted as a magnetic overprint during the Sveconorwegian mobile episode (1100-800 Ma). The lavas have low deuteric oxidation states but were subjected to widespread hematisation during later hydrothermal activity. The majority of the lavas, including the least altered, record a remanence with a mean D = 4°, I = −2° interpreted as a primary field direction, and an antiparallel remanence locally present in hydrothermal hematite; a Sveconorwegian overprint has displaced this at some sites. Stratigraphic sections identify a polarity history N→R in the lower sediments followed by N→R in the lavas. The post-Jotnian dolerites (D = 37° I = −33°) intruded at ca. 1250-1220 Ma did not achieve significant remagnetisation of the Jotnian rocks. Palaeomagnetic poles are at present insufficient to assign an age to the Jotnian rocks within the interval 1600-1250 Ma.

ISSN:0016-786X    

DOI:10.1080/11035898009450878

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009450879

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Both intermediate and monoclinic pyrrhotite occur in the Notträsk massive sulfide deposit. The monoclinic form makes up 5–10 wt.% of the total and occurs as lamellae oriented parallel to the (0001) crystallographic plane. The intermediate (hexagonal) pyrrhotite has been identified by X-ray powder diffraction methods. It consists of 11C type with a composition of 47.7 at.% Fe. The dimensions of the intermediate pyrrhotite supercell, based on a hexagonal unit cell, are ao= 6.8959±0.0014 Å and co=31.6109±0.0186 Å. The phase relations indicate that cobaltian pentlandite and monoclinic pyrrhotite exsolved at Notträsk when intermediate 1C pyrrhotite inverted to 11C pyrrhotite at a temperature of less than 250°C.

ISSN:0016-786X    

DOI:10.1080/11035898009450880

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009450881

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Jarosite minerals, i.e. iron (III) sulfates with the monovalent cations potassium, sodium and hydronium, have been identified at 13 localities evenly spread over Sweden. The end members jarosite (potassium), natrojarosite (sodium) and hydronium jarosite constitute an isomorphous solid solution series, with rather regular changes of cell-axes. A closer inspection of the cell-axes by refined X-ray diffraction methods reveals that the potassic variety dominates in the material examined. However, sodium and hydronium-dominant minerals have each been found in one sample. Jarosite minerals are formed under acid conditions with high redox potential. Suitable environments are sulfide mine dumps, where jarosites seem to be almost ubiquitous in small amounts.

ISSN:0016-786X    

DOI:10.1080/11035898009450882

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

All outcrops in a restricted area south of Kil, which interpolation between known outcrops suggests should lie in the Mylonite Zone, show no mylonitic or cataclastic deformation. In the same area more or less sudden changes in topography, lithology, degree of migmatite formation, tectonics, and type of deformation found in the Mylonite Zone occur. It is therefore suggested that there is a break in the Mylonite Zone south of Kil. A hypothesis involving original formation of the Zone at an as yet unknown time and later hinge faulting is put forward. The hinge is located at the break. North of the break the original Zone more or less coincides with the later fault but south of the break the later faulting occurred to the west of the ‘original Mylonite Zone’ and coincides with the Mylonite Zone as it appears on published maps.

ISSN:0016-786X    

DOI:10.1080/11035898009450883

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0016-786X    

DOI:10.1080/11035898009450884

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The orientation of the axes of the shatter cones from four different localities have been used in a preliminary determination of the impact center, which is situated about 7 km north of the topographical center of the Siljan structure. Its coordinates are 61°5′ and 14°56′E, which is close to the hill Järpåsen. The uplift of the central portion of the structure appears to be about 5.5 km. The apical angles vary between 70° and 91°. The difficulties of finding suitable localities for shatter cone measurements within the Siljan structure are discussed. It is suggested that excavations be made using explosives to obtain fresh exposures of shatter cones in rocks undisturbed by the Quaternary glaciations.

ISSN:0016-786X    

DOI:10.1080/11035898009450885

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor