companies or multinational companies (MNC) worldwide.
Any MNC registered in the host country, individually or as joint venture partner, is allowed to explore and mine all nonstrategic minerals with 100% foreign direct investment.
The participation of MNC in the mineral sector has far- reaching effects and benefits to the receiving country by way of readily available, specialized, experienced, skilled technocrats and advanced technology. Multinational exploration companies are global players equipped for specific groups of minerals such as iron-ore-aluminum, copper-zinc-lead, platinum-nickel-chromium, gold, dia- mond, oil and gas, and coal-lignite-coalbed methane (CBM). Global MNC include Anglo American PLC (London), Rio Tinto Group (London), Vedanta Resource PLC (London), BHP Billiton Ltd. (Melbourne), CSR Limited (Sydney), Cameco Uranium (Canada), Goldcorp and De Beers (Johannesburg), Exeter Resource Corporation (Canada), Codelco Mining Corporation and Capstone Mining Corporation (Chile).
demonstrated competent skills of engineering by making pillars with arches, and using wooden ladders and plat- forms, wooden launders for underground drainage, timber supports to prevent roof collapse, and clay lamps for mine illumination (Fig. 4.3).
The presence of small pits on the surface near to smelting sites and vast heaps of crushed debris near the mine opening indicate that zinc ore is crushed and richer
fragments are handpicked and ground before smelting.
Potholes of 30 cm diameter and 60e70 cm deep with rounded bottoms in hard calc-silicate outcrops are observed at Rajpura-Dariba, north of East Lode, India (Fig. 4.4).
The ancient zinc-smelting process was resolved through distillation and condensation technology (pyrometallurgy) of zinc ore using moderately refractory clay retorts.
Archaeometallurgical excavation at Zawar discovered intact ancient zinc distillation furnaces containing their full spent charge of 36 retorts (Fig. 4.5). Each furnace is 60 cm in height and divided in two parts: a lower condensing chamber, separated by a perforated plate from the upper
FIGURE 4.1 Ancient entry system to underground mine at shallow depth of orebody without any plunge during the 3rde2nd millennium BC at Khetri copper belt, Rajasthan, India.
FIGURE 4.2 Ancient entry system to underground mine at greater depth with orebody plunge to northeast at Rajpura-Dariba copper-zinc-lead- silver mine, India.
FIGURE 4.3 Ancient underground mining in rich zinc orebody at a depth of 172 m from the surface. Arching of the stope chamber shows high engineering skill. The wooden ladder (left) and platform (right) are still at an abandoned work site. Radiocarbon age dating indicates 3000 years from now at Rajpura-Dariba Mines, India.
FIGURE 4.4 Ancient potholes at the surface used for crushing, grinding, and concentration of rich zinc ore are still preserved at Rajpura-Dariba Mines, India.
main furnace of the distillation chamber. Smelting was carried out at 1100e1200C for 4e6 h. This site is recognized and preserved by the American Society of Metals as International Zinc Smelting Heritage in 1988.
A complete retort is cylindrical in shape with tappers at one end (Fig. 4.6), andfitted with an extended cylindrical hollow tube for channeling distilled hot zinc vapor from retorts in the upper chamber, which is condensed in the lower cooling chamber. The condensed zinc metal is dropped into a collecting pot. The exhausted retorts are either dumped or reused for making walls of hutments for the mining community (Fig. 4.7) in the township.
There is ample evidence of antique mining and smelting history as seen at the old deserted, ruined industrial town- ship in the valley area of Zawar Mines, India. The presence of an abandoned mine entry system in the surrounding hills, clay and sand-covered intact smelting furnaces, parts of broken-down residential walls, and Hindu temples (Fig. 4.8) of the 13th century AD in the center of ancient zinc-smelting site were discovered. Some of these historical monuments are maintained by the Indian Archeology Department.
In 1988 the ancient mining/smelting village around the old Zawar area was recognized by the American Society of Metals (ASM International) with the installing of a plaque as accreditation of the oldest zinc-smelting site (18035 BC) in the world (Figs. 4.8, 4.9, and 4.11).
4.3.4 Shear
The shear zone is the result of a huge volume of rock deformation due to intense regional stress, typically in the zones of subduction at depths down to a few kilometers. It may occur at the edges of tectonic blocks, forming dis- continuities that mark a distinct structure. The shear zones often host orebodies as a result of syngenetic or epigenetic hydrothermal flow through orogenic belts. The rocks are commonly metasomatized and often display retrograde metamorphism assemblage. An intense fractured or shear zone is a favorable structure to trap mineralization (Banerjee and Ghosh, 1997). The Hyde-Macraes Shear Zone, New Zealand, is a low-angle thrust system in which gold-bearing quartz veins have been deposited. The copper sulfide vein-type mineralization associated with migmati- zation in the southeastern part of Singhbhum Shear Zone, Jharkhand, India, is an example of shear-controlled copper- uranium mineralization.
4.3.5 Lineament
In general, mineral deposits occur in groups and follow a linear pattern along the fold axis, shear zone, and basement fracture traps (Roy, 2010). The linear alignment can be traced in a regional map of Aravalli Mountain, India, and McArthur-Mt. Isa province, Australia. Lineament mapping of different terrains using remote sensing images is capable of guiding groundwaterflow. Analysis of surface lineament with the help of geoinformatics became significant in oil and
FIGURE 4.5 Ancient smelting furnace unearthed with 66 numbers of retorts placed in an inverted position for distillation of zinc by a heating and condensation process at Zawar Mines, India, during 218035 years from today.
FIGURE 4.6 Ancient cylindrical distillation clay retorts from the smelting site at Zawar Mines area, India.
FIGURE 4.7 Ancient smelting retorts reused for the walls of a living shelter in the mining township at Zawar, India.
gas exploration as at Sabatayn mature basin in Yemen. A satellite image Enhanced Thematic Mapper-based analysis was conducted for extracting surface and subsurface linea- ments overlaying the seismic, magnetic, and gravity data.