As a company focuses on tin mining business, PT TIMAH continuously conducts exploration activity both onshore and offshore. The total number of mining Permit areas (IUP) owned by PT TIMAH onshore is by 331,580 hectares and offshore by 184,400 hectares. The exploration activity has been conducted for more than 50 years and now is still being expanded to increase the resources currently owned.
Generally the exploration activity comprises the following activities:
- Potential Area Identification; to obtain regional geology information.
- General Investigation: to discover inferred resource.
- Prospect Drilling: to discover indicated resources.
- Production Drilling: to discover measured resources.
The measured resources obtained are then submitted to the mine planning work unit, to be used as feasibility study.
I. Exploration Basic Concept
Exploration in mining industry is an effort to discover hidden resources; neither to find lost things nor to invent new things. Hence the exploration activity is restricted to economic boundaries and complies with good geological concept.
Mining companies, followed with good planning, should consider exploration activity as long-term planning in achieving company’s vision, especially in assuring reserved ownership and determining future business course (Riddler, 1989). Therefore, exploration should become a long-term commitment which needs careful planning for mining companies.
PT TIMAH, as one of mining companies, has a strong commitment in carrying out exploration activities in order to discover new resources for the sake of Company’s development. The outcome of exploration activity is expected to be significant factors in directing Company policy.
Tin Sediment Geological Concept
PT TIMAH’s core business in tin mining has driven the Company to implement geological concepts used in tin exploration activities.
In general, there are two kinds of compositions of tin sediment: primary and placer tin sediment. Primary tin sediment is the sediment of tin ore remained in the tin carrier rock or in the rock where tin ore is formed. Tin carrier rock in Indonesia is Triassic granite which was spread across China, Thailand, Malaysia, Bangka Belitung Island to the west of Borneo. This line is commonly called as tin belt zone.
Placer tin sediment is the type of sediment that was shifted out of the source rock and sedimented in a new place as due to the process of weathering, transportation and reprecipitation.
- Primary Tin Sediment Formation Process
Primary tin sediment is formed as a part of magmatism process of granite formation–an acid igneous rock. In the final formation phase, at 800o to 400o Celsius, magma contains much gas as the remaining solution such as SnF4. The compound then reacts with water (H2O) to form SnO2 (Casiterite) mineral and HF. In Indonesia, This Casiterite minerals then become the mineral carrier of tin sediment.
The remaining solution contains gas which enables to move easily filling voids and crevices of rocks on top of it. Thus the primary tin deposition stuck at the top of the granite body, in crevices and cavities of rocks that are in it.
Bangka and Belitung have abundant primary tin sediments which mostly found on weathered rock, making it easier to conduct mining activity.
B. The Formation Process of Pacer Tin Sediment
Tin placer sediment is often called as alluvial tin sediment since most of its sediment is formed on the land (alluvial). Although its existence currently is mostly in the sea, its condition is still in the form of alluvial during sedimentation.
There are several factors which determine the formation of placer tin sediment: the help of a tin carrier source (S-type granites), the process of weathering, erosion, transportation and sedimentation, as well as a valley or basin for the container of weathering material.
Typology of tin placer sediment consists of alluvial sediment, colluvial, fan sediment, stream sediment, wetlands and coastal sediment. Most of the tin sediment found in Indonesian tin islands is stream sediment (alluvial).
II. Tin Exploration Activity
Currently PT TIMAH, in addition to conducts geological survey, operates several geophysical equipments, Bangka drill, mechanical drill and some drilling ship equipments, as some supporting exploration activities. The geophysical equipments owned by the Company are: seismic, magnetic and geoelectric equipment, mechanical drilling equipment and some units to conduct coring drilling on land and some drilling ships used to carry out drilling activities on sea.
The exploration activity concept conducted by PT TIMAH to discover primary tin sediment is by implementing the geological, petrology and geochemistry structure approach. While the concept of exploration activity is carried out by an approach of mother rock hunting, valley hunting and gravel pact hunting. This concept has been conducted for years and still effective until present. PT TIMAH also implements other concepts such as depositional environment hunting (facies), mineralization and stratigraphy sequential used as addition and development.PT TIMAH annually allocates more than Rp150 billion for exploration activities. Currently the activities have been increased to discover more potential deep primary and alluvial tin sediment. Besides, PT TIMAH also actively engages in exploration activities of gangue minerals and rare earth element.