THE IMPORTANCE OF TECTONIC SETTING IN UNDERSTANDING ORE DEPOSITS

If a geological concept is to be of interest to Explorationists it must have both spatial predictive utility and be more economically efficient to apply than available direct detection technology. In general, the application of Predictive Concepts is most effective at the larger (ie global to camp) scale and Direct Detection technologies tend to be more effective at smaller (ie camp to deposit) scales. In this context, tectonic setting is extremely relevant to the exploration industry.

The links between ore deposit type and tectonic setting have been recognised since the first applications of plate tectonic theory to economic geology in the early 1970s. These have become much better understood in the three decades since then but we still have much to learn. The implications of the links between ore formation and tectonic setting are obvious. Particular ore types are restricted to particular tectonic environments, impacting on area selection strategies at the most fundamental level. However, the ore-tectonic setting link can work in the other direction; given an occurrence of mineralisation, a knowledge of the tectonic environment can help us assess its significance.

It is now also clear that tectonic/geodynamic setting impacts on the most critical issue for our business; finding those few giant deposits that contain most of the industry’s value. We know that the factors which discriminate giant ore deposits from similar, more abundant smaller examples are not principally deposit scale effects. Instead, we now recognise that the formation of a giant ore deposit is the product of large scale geodynamic process, requiring the input of a large amount of energy to concentrate metals from a vast volume of rock. Given this understanding, our predictions of mineralisation potential are more closely tied to our understanding of tectonic setting than ever before.

The new perspective is that tectonic setting is far more than just a “passive” framework on which mineralisation processes are superimposed. Rather, a particular sub-set of geodynamic processes are the ore-forming processes, and the relative magnitude of these processes relates to the potential to form giant ore deposits. The challenge is to elucidate these geodynamic processes and develop the capability to recognise them in commonly available data sets.