BUTHTHALA MAGNETITE DEPOSIT

Introduction and Origin of Deposit

The crystalline Precambrian metamorphic rocks which have been subdivided into three major subdivisions, Highland Complex (HC), Vijayan Complex (VC) and Wanni Complex (WC) covers more than 90% of the island of Sri Lanka and the rest is mainly Jurassic and Miocene sedimentary rocks.

The rocks of the HC are generally metamorphosed to granulite facies and both VC and WC are metamorphosed to upper amphibolite facies. Granulite grade khondalite-bearing metasediments, migmatites and granitoid gneisses and charnockites form the HC while orthogenesis and migmatites of amphibolite facies complexes form both the WC and the VC.

Some granulite-facies outliers comprising rock types similar to those of the HC are exposed in the southern part of the VC, not far from the southern coast near the villages of Buttala and Kataragama.The boundary between the Highland Complex and Vijayan Complex; their lots of minerals are formed.

E.g.: Magnetite, Serpentinite, Vein quartz, Cu-magnetite.

Magnetite is a once of iron-bearing mineral. Magnetite deposits belong to Precambrian period and occurring at some depth. The magnetite deposits can find several places in Sri Lanka. They are at Wilagedara, Panirendawa, Seruwila and buttala.

The Buttala Magnetite deposit has been discovered recently. The deposit was situated boundary between the Highland Complex and Vijayan Complex. The deposit consists of three main bodies of magnetite intruded into NS trending country rocks. The exposures of these bodies vary in thickness from 1 to 20 m. The linear extent of the deposit is about 2 km with minimum local vertical relief of 150 m. The investigations have revealed that the main mineral constituent of the deposit is magnetite (Fe304), exceeding 90% in concentration.

The preliminary geophysical investigations have also confirmed that the deposit extends to depths below 30m. In addition to the main deposit, scattered occurrences of smaller magnetite bodies were observed in an area of about 10 sq. km.

Granulite-faces outliers comprising rock consists small amount of some other minerals in addition to the magnetic deposit. They are,

Feldspar, Quartz, Pyrite, Pegmatite, Mica, Etc.

According to the researchers that have conducted on the deposit revealed that the deposit was not spread throughout the total area and it was formed as a dike which dipping to the southeast direction.

The particular area has been subjected to extensive weathering resulting flat land with a few series of hill rocks. Quartz with small magnetite boulders were contained in the lower part of the hillock and upper part mostly contained with large magnetite boulders. Not only quartz and magnetite, hematite and granite-like minerals and rocks also were found during the magnetite ore visit.

Granite Quarry

The Quarry has located near to the magnetite deposit. Currently, it is not functioning. Due to the leach of iron, granite will be staining. Also due to the high mineralization C percentage of the granite is less. So it is not good for the constructions. There many types of minerals were found from there, such as,