| 1. |
- Widenfalk, Lennart, et al.
(författare)
-
A multidisciplinary investigation of the Notträsk Gabbro, northern Sweden
- 1985
-
Ingår i: Geologiska föreningens i Stockholm förhandlingar. - : Informa UK Limited. - 0016-786X. ; 107:2, s. 109-126
-
Tidskriftsartikel (refereegranskat)abstract
- The differentiated, sulfide-bearing gabbro near the city of Boden in northern Sweden has been investigated in order to get a plausible model for its formation, shape and age. The gabbro is associated with a major fault system along which several intrusive bodies occur. The largest of these has been traversed by a gravimetric, magnetometric and geological profile. The investigated intrusion is undeformed and oval-shaped and covers some 20 km2. The outer parts of the body consist of a norite in contact with older meatasediments and granites of varying age. Inside the norite occurs a magnetite-rich gabbro, which forms a ring around the centre of the massif, which in turn consists of leucogabbro-olivine gabbro. Fe, Ti and K are low in the centre where Mg and Cr have their highest contents. Impregnations of sulfides and a massive pyrrhotite vein with some 1 % Ni are located in the norite. A number of intrusion models have been tested by computer modelling combining gravimetric and magnetic field data. The most probable model seems to be a funnel-shaped body pointing downwards. The different gabbro types dip steeply inwards indicating vertical zones rather than horizontal. Palaeomagnetic measurements show that the intrusion has a similar orientation of magnetization as other gabbros of the Haparanda series in northern Sweden (1800-1900 Ga, Rb-Sr). Furthermore, the pole distributions show that the rock cooled slowly, which may indicate that the present outcrop is a deep part of an eroded intrusion. The massif is supposed to have been formed by a diapiric re-emplacement of primary horizontal cumulates formed in the sequence olivine gabbro-leucogabbro-magnetite-bearing gabbro-norite.
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
|
|
| 6. |
- Brindt, Lars, et al.
(författare)
-
Direction dependent interpolation of aeromagnetic data
- 1985
-
Ingår i: Machine Processing of Remotely Sensed Data. - West Lafayette, Ind : Purdue University Press. ; , s. 86-95
-
Konferensbidrag (refereegranskat)abstract
- A method for level correction and interpolation of anisotropically sampled aeromagnetic data is described. The level-correction is based on a piecewise comparison of adjacent flight-lines. The interpolation scheme is based on cubic splines and preserves thin linear structures in anisotropic potential field data. The design of such a method is seen as an important building block in the design of an image-based information system for geologic applications
|
|
| 7. |
- Dyrelius, D., et al.
(författare)
-
Bergarters fysik
- 1985
-
Ingår i: Geofysik. - Uppsala : Svenska fysikersamfundet. - 9186344285
-
Bokkapitel (populärvet., debatt m.m.)
|
|
| 8. |
- Ehlin, Per-Olov
(författare)
-
Birch leaf compositions above different types of bedrock in glaciated areas
- 1985
-
Ingår i: Geologiska föreningens i Stockholm förhandlingar. - : Informa UK Limited. - 0016-786X. ; 107:3, s. 223-231
-
Tidskriftsartikel (refereegranskat)abstract
- Birch leaves (Betula alba) as well as Ao, A2, B2 and C soils can rarely indicate the underlying rock type. Plants may show only anomalous concentrations of characteristic elements such as Ca above limestone and Cr or Ni above gabbro. If the plant compositions are used to distinguish types of basement rock, they could differentiate slightly between limestone and quartzite, limestone and granite, and porphyrite and granite, using their Ti, Al and Cu data, respectively. B2 soil analyses could differentiate between limestone and silicate rocks in the basement, using Ca or Mg data. Plants have also a limited capacity to reflect the underlying soil; only Fe data are highly correlated with those of C and Ao soil. Compositional correlations between plants and soil or rock are strongest in wetlands
|
|
| 9. |
- Elming, Sten-åke
(författare)
-
A palaeomagnetic study of Svecokarelian basic rocks from northern Sweden
- 1985
-
Ingår i: Geologiska föreningens i Stockholm förhandlingar. - : Informa UK Limited. - 0016-786X. ; 107:1, s. 17-35
-
Tidskriftsartikel (refereegranskat)abstract
- This palaeomagnetic investigation comprises basic rocks from six localities from the Svecokarelian zone in northern Sweden. Most of the pole positions in this study and other reported poles of Svecokarelian and post-Svecokarelian rocks fall within an approximately 12 degrees wide band running from east to west representing ages of magnetizations from 1880-1700 to ∼ 1530 Ma. Thermal demagnetizations of specimens of the probably oldest massifs indicate a possible backward continuation of the polar wandering path. Mineralogical studies of thin sections of the rocks show ore symplectites and myrmekitic textures indicating a slow rate of cooling at least at the end of the rock formation. Signs of metamorphism are demonstrated by the existence of secondary minerals, including magnetite, not related to late magmatic alterations. The distribution of site means as well as the change of directions of the remanence vectors during thermal demagnetization can be explained by a slow rate of cooling and where signs of metamorphism exist by partial remagnetization of the rock. This study has, apart from the palaeomagnetic results, demonstrated the difficulty of correlating radiometric ages with ages of magnetization
|
|
| 10. |
|
|
