By Nandkumar M Kamat
With a metallurgist as the Chief Minister of Goa, the question is whether the best global public funded geochemical database practices would be followed in acquiring detail, geochemical information on what is actually available in the auriferous laterites in Goa?
A state mining policy (only iron, manganese, aluminium centred) based on questionable, incomplete and outdated geochemical databases would be a mockery. The major aim of the governments in Goa is to discourage in house geochemical research and offer only crumbs to people by way of information on mineral resources. Since laterite covers most of Goa, a laterite geochemical atlas of Goa is urgently required based on the model prepared by CSIRO, Australia. A soft copy of this report (readers may access it from http://www.crcleme.org.au/Pubs/OPEN FILEREPORTS/OFR228/OFR228.pdf) has been mailed to the Chief Minister as a model to be adopted in Goa for public funded geochemical prospecting of gold in auriferous laterite. Whether state government adopts such proactive approach or not, laterite all over Goa would continue to be excavated and used and there would not be any end to environmental problems.
This is a model of utter foolishness when the state can’t pay a public debt of Rs 6000 crores. Very little efforts are required to separate auriferous minerals from lateritic materials. Gold can be easily separated from powdered laterite. No chemical treatment is required. The gold free laterite powder can be used for eco friendly brick making by modifying technique developed by Engineer Dias.
In fact Prof Karmarkar from Goa Engineering College, Farmagudi, had undertaken a project to convert the lateritic waste into building blocks. Engineer Anthony Dias from Salcete had done his own independent investigations and produced building blocks from lateritic mining waste compressed under very high pressure. The blocks which he produced in 1996, weighed 18.5 kgs each having 16 kg of lateritic waste and the rest comprising the binding material such as sand, cement and moisture. These blocks had a crushing strength of 15 to 20 MT as compared to 10 MT for naturally quarried lateritic blocks (locally known as chiro or chire). These blocks were found to resist pounding by the monsoon and erosion proof.
In 1996, a similar cement concrete block cost Rs 8.50 to 9 in Goa. The blocks made by Engineer Dias from mining waste had Rs 6.25 as production costs. On this basis he had projected the immense potential of block production industry. If every year, 25 million MT of lateritic waste produced by all the mines in Goa is used (as per 1996 figures) then Engineer Dias had then estimated that, 1563 million blocks could be produced. In 1996 he had shown that if these blocks were sold at Rs 7.50 each, then the yearly sales turnover would be Rs 1172 crores. But no government in Goa since 1995 had cared to take his assistance. This shows how little importance the mines and environment departments give to innovative ideas.
The mines department has virtually nothing to offer on geochemistry of laterites in Goa. Why should it care for loss of gold from laterite excavation? Therefore, an NGO of stakeholders in geology teaching and research, the Geological Society of Goa need to be richly complimented for getting a very important, in depth researched article by Mike Widdowson, department of earth and environmental sciences, Open University UK on ‘evolution of laterite in Goa’. Although he has chosen to remain silent in the full paper about auriferous nature of laterites in Goa, a geochemist can read a lot in between the lines. He remarks that south of Malvan in Goa, Karnataka and Kerala states the coastal laterites have evolved upon the highly heterogeneous pre-Deccan basement which comprises Archean-proterozoic age gneisses, greenschists, irregular shaped Proterozoic mafic intrusions and occasionally, over patchy Late Cenozoic sediments that blanket the basement at some localities. He also mentions that long-term climatic and tectonic stability, together with slow geomorphological evolution over periods of ten thousand to a million years are significant to the development and destruction of laterite profiles. Widdowson analysed 10 major elements and 15 trace elements by XRF from Merces laterite quarry from surface to 34 metres depth. This laterite is developed over proterozoic greywacke.
Many proterozoic rocks contain gold, so it is but natural that gold would be detected in laterite. Widdowson found highest aluminium and Titanium concentration at the depth of 3.5 metres. Iron was highest at the depth of 7.5 metres. Manganese was highest at 34 metres. He reported Rb, Sr, Y, Zr, Nb, Ba, Pb, Th, U, Sc, V, Cr, Ni, Cu, Zn as trace elements in laterite. Chromium, Vanadium and Zirconium showed highest values at the surface. It is intriguing to find that Mike’s work was not seriously followed up. The billions of tones of laterite deposits in Goa need a detail in depth geochemical analysis. Government needs to prepare a geochemical atlas of major elements and trace elements in these deposits.
If necessary there is no harm to take the help of either Mike Widdowson or the Australian geochemists from CSIRO Australia’s Cooperative Research Centre for Landscape Evolution and Mineral Exploration. This information needs to be given to the respective village panchayats and the gramsabhas so that people know what exactly they are losing when laterite quarries are permitted. Under no circumstances auriferous of gold containing laterite deposits should be allowed to be exploited.
Australian geochemists (Smith and others, 1997) have recommended only those analytical methods in laterite geochemistry should be used, that give the total amount of an element present. This will commonly involve more than one method to give coverage of the elements required, e.g., combinations of instrumental neutron activation analysis (INAA), inductively coupled plasma with fusion for digestion (ICP), ICP mass spectrometry (ICP-MS), and atomic absorption spectrophotometry (AAS).
If there is a boom in gold market then it is obvious that the first priority of any government which has the knowledge of auriferous rocks in the western Dharwar craton found in Goa should be to look carefully at the ongoing mindless and low value plunder of basically auriferous Iron ore. The auriferous lateritic overburden once considered as ‘reject’ could now become a source of extracting gold. There is employment and a way to get the capital and resources to repair and restore Goa’s over-mined landscape. Village panchayats should come forward to extract gold from laterite (and alluvial auriferous sand and dead mining rejects where available) on a cooperative basis. The road to draw the roadmap for Goa’s sustainable future would indeed be golden if people participate, benefit and profit equitably.