STUDENTS INDUSTRIAL WORK EXPERIENCE SCHEME (SIWES) DONE AT CROUSE ROCK INDUSTRIES (NIGERIA) LIMITED,ISHIGG, IVO LOCAL GOVERNMENT AREA OF EBONYI STATE
REVIEW OF THE GEOLOGY OF THE AREA AND THE EXPLORATION TECHNIQUE EMPLOYED.
2.1 REVIEW OF THE GEOLOGY OF THE AREA
Ishiagu, the location of crushed rock industrial (Nig) ltd, is a town in Ive local government Area, Ebonyi State. Its geological setting lies entirely on that of the lower trough. The lower Benne trough is part of the Benue depression (cartel et al.,1963); comprising mainly the Abakaliki anticlimactic and the Afikpo syncline to the east and the Anambra basin to the west. This basin was initiated by opening up of the south Atlantic and marine inclusion into the Benue trough.
The sedimentary units in this area are generally cretaceous in age (Nwachukwu, 1972).
From findings by Reyment, 1965, Kogbe, 1975; Adegoke, 1969; Ishiagu is underlain by the Asu River group (Albian), and bordered on the south by the Eze Aku Shale. The Asu river group is the lowest and hence by principle, the oldest lithostratigraphic unit of the cretaceous age laid within the Benue trough.
The Benue trough originated from early cretaceous rifting of the central West African basement uplift, forming a regional structure which is exposed from the Northern frame of the Niger-Delta, and runs North Eats for about 1000 km to underneath lakechad is part of an early cretaceous rift complex known as the west and central African rift system.
The ASU River group consists of largely brown sandy shale with fine grained miraculous sandstones. These shales grade into a subordinate sandstone fancies. It is fine to medium grained, thinly bedded to massive, poorly sorted and grayish white to brown in fresh and weathered samples respectively Reyment (1965) and Uogbe (1975).
Whiteman (1972), reveled by minor basic and intermediate intrusive during the santonian period. These intrusions outcrop around Ishiagu. These igneous intrusions occurring within the Asu River group post – Albion events. This is explained in the geologic history of Ishiagu which shows that majority of the sediments were deposited during the Albion stage, when the general topography was flat, until the tectonic activities during the santonian which deformed there rocks (kogbe 1975).
2.2 RELIEF AND VEGETATION OF THE AREA
2.2.1 RELIEF OF THE AREA
The general relief of the area is characterized by hills and villages. Majority of these hills and villages are aligned in the NW-SE direction, conforming to the orientation of the folds from the santonian orogenic deformation,
The area is well drained with the general river (the Ivo River), flowing in the NE-SW direction. Majority of the rivers return in the Northern part and merge as tributaries to the Asu River, while the general surface water flow pattern conforms to the fold axis (koogbe 1975).
The drainage pattern of Ishiagu is dendrite.
Ishiagu is characterized by thick and dense vegetation, typical of the tropical rainforest. The fine grained soil; mostly clay and shore, silt and a mixture of these and sands aids in a favorable growth of the plants.
2.3 DESCRIPTION ROCK QUARRIED AT CRI (NIG) LTD, ISHIAGU
The rock quarried by the company (crushed rock industries (Nig) Ltd is an intermediate type of igneous rock of plutonic origin.
From fresh samples obtained from the pit, where these rock are extracted, studies show that the rock is a diorite (Nwachukwu, 2011) magascopically, the rock has black to dark grey and motted black and white colours. They show quite close resemblance to granites.
Some of these rock samples contain a segregated portion consisting of calcite, suspected to be a secondary mineralization along fractures or cavities, resulting from hydrothermal crystallization. Thin quartz veins are also eminent features. Generally, light coloured minerals such as felsic minerals (feldspar plagioclase of sodic group, eg Albite ) and muscovite are preset. It also contains Biotite, hornblende and pyrxenes. Pyrite may be present as an accessory mineral.
The intrusive bodies have domelike shape arching the overlying sediments, and can be described as massive laccoliths. From the zero to thin overburden sedimentary rock, the Ishiagu intrusion can be said to have been emplaced as a shallow depth (Nwachukwu, 2011). The developed lacolith structures and the abundance of round vesicles in some parts of the upper boundary suggest the same. The rock is massive.
2.4 EXPLORATION OF INTRUSIVE ROCKS
A three – fold procedure is employed in exploration of intrusion igneous rocks by the company.
- Physical observation of features
The relief and vegetation of the area are such observations taken note of. Hilly landscape and presence of igneous rock masses or bounders are likely features of an intruded area. The intrusion lead visibly to the impregnation and uplift of the environment where it occurred, the hilly landscape.
- Geophysical survey
Geophysical methods are relevant in such surveys for deep sitted rocks which may not be reached ordinarily Resistively and electrical methods are used in the exploration process density differences can also be employed, as the igneous intrusion is expected to have a density different from that of the surrounding country rocks.
This density differences is used in delineating the intrusive from the country rock.
- Secondary exploration/test drilling of suspected intrusive igneous fields.
When a site with such potentials of abounding these intrusive has been delimited, the square plot by square division of site marking method is employed before embarking on a drilling exercise.
The first drilling exercise done on the site is to conform the existence of the igneous bodies. When bed rock is hit by the drilling machines, are samples blow out of the hole as dust are tested in the laboratory.