Mining reconciliation is the comparison of estimated tonnage, grade and metal with actual measurements. The aims are to measure the performance of the operation, support the calculation of the mineral asset, validate the Mineral Resource and Ore Reserve estimates, and provide key performance indicators for short and long-term control (Morley, 2003). Ongoing, regular and efficient reconciliation should also highlight improvement opportunities and allow for proactive short-term forecasting by providing reliable calibrations to critical estimates. The concept is that of “measure, control and improve”.  <...>

Epithermal gold deposits in Chile are Cretaceous to Cenozoic in age. The ores and the volcanic rocks with which they are associated were generated at a noncollisional, ocean-continent convergent plate margin. They are related to long, slightly sinuous north-northeasttrending magmatic belts roughly parallel to the Pacific coast. Most of the deposits are associated with eroded volcanic centers and subvolcanic porphyries. North-south variations in the nature, extent, and timing of magmatism control the succession of mineralization events. In the Late Cretaceous, vein districts (e.g., E1 Bronce) and hydrothermal alteration zones were formed in central Chile.

Both the petroleum industry and academia continue to undergo a transition whereby active knowledge transfer by experienced earth scientists represented by faculty teachers and researchers, Chief geoscientists, etc. is rapidly changing to passive knowledge (or data transfer) through a variety of electronic media and systems. Over the recent past, the broad experience base in both industry and academia has been phased out through retirement, redundancy and focus on specific research areas. In the case of industry, a new generation of younger specialists, sometimes called Nintendo geoscientists, are trained to solve specific practical problems based on highly focussed data acquisition and interpretation using work stations. In academia, an increasingly holistic focus on earth systems science is eroding the broader geological base that has hitherto underpinned scholarly research. <...>

Stratigraphy lies at the heart of geology and we have set for ourselves the rather daunting task of describing, albeit in summary fonn, the regional stratigraphy of North America. Our purpose is to develop a stratigraphic framework against which to view the history of the continent and with which to test ideas about Earth mechanics. No such treatment can ever be complete, as ours is not, but we hope the attempt will provide the reader with at least a working summary of North American stratigraphy and geological history.