Databank

Workreport 2016-63

Back

Name:

Lithology and Structure of the Investigation Trench OL-TK10

Writer:

Kärki, A.

Language:

English

Page count:

34

Summary:

Geological mapping of the investigation trench OL-TK10 was carried out in 2005 by the employees of Posiva Oy and subsequently augmented by the methods of digital photograph interpretation. The results of the studies are presented in this report. The area of the trench is approximately 900 square metres and it has the length of ca. 35 metres in the N-S direction and 30 metres in the E-W direction.

The bedrock in the area of the trench consists mainly of supracrustal high-grade metamorphic meta-pelites, meta-arenites and intermediate, pyroclastic metavolcanic rocks which were metamorphosed under upper amphibolite facies conditions to various metatexites and diatexites. Layer-structured metatexites cover the most part of the trench whereas dike-structured metatexites and schlieren-structured and nebulitic diatexites exist in lesser amounts. In addition to those, wide leucosome bodies or granitic pegmatoids occur at places.

Ductile deformation structures of four major stages are described and a complicated structural sequence is identified from the trench. Metamorphic banding, S1 was isoclinally folded by the stage D2 simultaneously with strong migmatization. These structures were overprinted by the F3 folding leading to the generation of the close and open fold elements. By the stage D4 the bedrock was once more deformed and often close fold elements were developed as the latest components of the final interference structures.

Zones of extremely strong fracturing are missing in the area of the trench but some regional variation in the fracture density and in their directions is detectable. Two sets of steeply dipping fractures can be distinguished from the whole fracture population. The first set is approximately in the ENE – WSW direction and the second set in the NW – SE direction. As a whole, the fractures detected in the area of the trench are rather short, often less than 2 m in length, the measured dips of those are mostly steep and their aperture is not often detectable from the surface section.

Keywords:

Investigation trench, lithology, ductile deformation, fracturing, nuclear waste disposal.

File(s):

Lithology and Structure of the Investigation Trench OL-TK10 (pdf) (16.1 MB)


Back


Share article:
This website stores cookies on your computer. These cookies are used to improve our website and provide more personalised services to you.
Close

Cookies

To make this site work properly, we sometimes place small data files called cookies on your device. Most big websites do this too.

1. What are cookies?

A cookie is a small text file that a website saves on your computer or mobile device when you visit the site. It enables the website to remember your actions and preferences (such as login, language, font size and other display preferences) over a period of time, so you don’t have to keep re-entering them whenever you come back to the site or browse from one page to another.

2. How do we use cookies?

A number of our pages use cookies to remember your actions and preferences (such as login, language, font size and other display preferences.)

Also, some videos embedded in our pages use a cookie to anonymously gather statistics on how you got there and what videos you visited.

Enabling these cookies is not strictly necessary for the website to work but it will provide you with a better browsing experience. You can delete or block these cookies, but if you do that some features of this site may not work as intended.

The cookie-related information is not used to identify you personally and the pattern data is fully under our control. These cookies are not used for any purpose other than those described here.

3. How to control cookies

You can control and/or delete cookies as you wish – for details, see aboutcookies.org. You can delete all cookies that are already on your computer and you can set most browsers to prevent them from being placed. If you do this, however, you may have to manually adjust some preferences every time you visit a site and some services and functionalities may not work.

Close