* New technologies target deposits "hidden" by soil, rock, ice
* Change could mirror transformation seen in oil and gas
* Cheaper, more efficient drilling needed to unlock deep deposits
By Clara Ferreira-Marques
LONDON, Dec 5 (Reuters) - From intelligent drills to analysing gum tree leaves, an unprecedented push to develop new methods and technologies promises to transform the way miners explore for deposits, allowing them to dig deeper, faster and more cheaply.
The results could ultimately unlock so-called 'covered' deposits: riches hidden under hundreds of metres of soil, rock or sea water, sometimes in or near previously explored areas.
That could reverse the steady shift away from mining regions such as Australia and Canada to untested, frontier areas, in the search for the next blockbuster find.
Many flagship mines are ageing, producing less and less metal for every tonne of ore pulled out of the ground. This has driven up costs and prompted companies to explore in new parts of Africa or Asia, despite the additional political risks.
"Deposits are becoming increasingly hard to find, and both the technology that we have available to us and the approaches, are less useful when exploring deeper deposits," said Dean Collett, a geoscience consultant working with Australia's UNCOVER initiative, which promotes exploration of covered areas.
"The industry needs technology and improved geological insight to crack this."
Change could now be closer, thanks to a string of academic, government, company and combined initiatives like UNCOVER - many borrowing from innovation in the oil and gas industry, which is already drilling far deeper than a few decades ago.
Roughly 80 percent of Australia, for example, is under 'cover', which means the overwhelming majority of exploration and mining activity - 90 percent by some estimates - has been carried out on only a small portion of the vast country, the slice where rocks above ground hint at the riches below.
"The laws of probability say that there must be an equal proportion of deposits sat under that cover. There is nothing unique about the geology that is sticking out - it just happened to be higher than the rest," says Stephen McIntosh, head of exploration at mining major Rio Tinto.
"There have to be a lot more plums in the plum pudding as we advance through depth, and we are starting to see that."
Many in the mining industry compare the potential change to that seen in oil exploration in the Gulf of Mexico. Thirty years or more ago, it was the "Dead Sea", as shallow wells began to run dry and companies could not tap oil in deep water.
It has since boomed, thanks to seismic equipment - some of it now used in new mining initiatives - that allowed explorers to penetrate layers of rock, while engineering innovations transformed the ability to drill at depth.
For countries like Australia and Canada, it is about reversing exploration decline on their turf. Currently, 80 percent of Australia's production comes from mines that were discovered more than 30 years ago.
For miners, even at a time of belt-tightening, it is about securing future supply, satisfying the investor push to get more out of every dollar spent hunting for new mines - potentially altering a balance that has seen miners prefer to tackle political risk than technical challenges.
Initiatives ranging from improving geophysical and geochemical techniques - even the measurement of metal traces in eucalyptus leaves and kangaroo excrement and some methods first developed as far back as the Second World War, to track submarines - are already transforming how exploration works.
Analysis of so-called "roo poo" may give insights into the minerals that are contained in the plants that kangaroos have fed on and are then concentrated in the animal itself.
Superconducting Quantum Interference Devices (SQUID), for example, are sensitive magnetic sensors that can detect deep, magnetic sulphide ore bodies and distinguish them from other conductive material, like rock. Versions of the technology have already been put to use by companies like mining giant Anglo American in exploration in Finland under sediment deposited by glacial ice, contributing to a significant find.
Similarly, the Las Cruces copper deposit in Spain, now part of First Quantum, was discovered through anomalies in gravity measurements that led the exploration team past where the Iberian Pyrite belt - which crosses Portugal and Spain - was thought to end.
The British Geological Survey is using small aircraft to gather magnetic and radiometric measurements across the south west of England, including Cornwall and Devon, where tin, copper and other metals were mined for centuries.
"This survey will give us a pretty good idea of how much modern technology will reveal, over and above what is already known, in a pretty intensively studied area," said Neill Wood, of the Camborne School of Mines at the University of Exeter.
A large part will be not just about identifying deposits and increasing the ability to "see" underground, but about being able to drill at reasonable cost. Drilling a deposit 2.5 km below the surface can, depending on the contract and location, cost $500 per metre - an almost prohibitive charge.
Australia's Deep Exploration Technologies Cooperative Research Centre (DET CRC), a government and industry backed effort to cut that cost and speed up deep drilling, has worked on prototypes including a coiled tubing rig.
This uses a reel of tubing and eliminates manual handling of drill rods - costly and dangerous - and it has a motor at the bottom of the hole, cutting fuel costs.
Research there also aims to help teams analyse findings immediately rather than having to extract metres of core, or sample tubes of rock pulled out and sent offsite for tests.
"Hopefully this can mean a quantum change in the way we explore at depth," said Richard Hillis, chief executive of DET CRC. "You'll have several shots at finding the needle in the haystack and try and move towards it, rather than one shot."
For the industry's majors, the appeal is an ability to combine approaches: deeper exploration and better visibility in covered areas, but also traditional methods in existing regions.
"In Chile, for example, there have been quite a lot of recent discoveries in old mining districts. Some of these areas that are considered mature and well-explored," said Tracey Kerr, head of exploration at Anglo American. "I think you have to be a little more open-minded about the potential."