SHRIMP II Applications

  • Examining stellar nucleosynthesis.
  • Calibrating the Palaeozoic time-scale.
  • Dating of the Earth’s oldest crust.
  • Examining the oldest zircons in the solar system.
  • Measuring trace elements in diamond inclusions.
  • Investigating Ti isotopic ratios in meteorites.
  • Determining Pb isotopic composition of lunar granites.
  • Paleoclimatology from oxygen isotope ratios in fossil apatite.

Mineral Exploration.

SHRIMP zircon dating has led to improved understanding, for example, of the timing and origins of mineralisation of the giant Olympic Dam copper-uranium-gold-silver deposit in South Australia, gold-copper deposits in Tennant Creek area of the Northern Territory, the gold and nickel deposits of Western Australia and Canada. The versitility of SHRIMP in fields of other than uranium-lead dating has been illustrated graphically by probing the composition of sulphur at the micro scale in the sulphide minerals that form metal ores. Vital new understanding of the origin of mineral deposits around the world has resulted.

The isotopic composition of sulphur in the giant base metal ore bodies which supply most of the world’s copper, zinc, lead and silver is sensitive to whether that sulphur is derived from sediments or from hot fluids originating deep in the Earth. Knowing the source of the sulphur for each ore body helps in determining why metals were deposited and directs the exploration strategy adopted in the search for new ore bodies.

Conodonts used for determination of Ordovician Sea Temperature

Oil Exploration.

Exploration of oil is a technically sophisticated and fiercely competitive international business. The cost of trial wells, often dry is huge, and millions of dollars are saved if location of oil can be predicted more accurately prior to drilling. The same applies to finding mineral deposits such as gold, copper and nickel ores buried deep underground. The exploration industry therefore relies increasingly on modelling how, where, and when these commodities form and become trapped in rock structures, so as to target drilling in a risk-efficient pattern.

Geologists learn about oil and mineral formation by close study of the crystals that form rocks. One key mineral is zircon, a crystal just a few thousandths of a millimeter in size that contains trace amounts of uranium (typically one hundred parts per million). The time of formation of rocks and mineral deposits can be measured in millions of years from the progress of the uraniums natural and regular radioactive decay to form lead. This gives vital information on when rocks crystallised, when mineral deposits where emplaced, and when traps suitable for oil were being formed.

Zircons have several concentric zones of growth, rather like tree rings, indicating they have crystallised in stages over periods of many millions of years. Conventional methods of dating zircons involve chemically dissolving the crystals in a beaker, and placing the solution in ag formed.

The science of dating therefore urgently needed a new type of mass spectrometer capable of probing, and dating, the individual zones of crystals. SHRIMP II was developed in response to this need.

In oil and gas exploration, a clear need exists for accurate calculation of rates of basin substance, sedimentation and sea level change and their correlation with crystal movements. In sediments which carry no fossils to aid dating, such calculations have carried unacceptable levels of error. SHRIMP zircon dating is bring a new level of accuracy to the study of the process that form the sedimentary basins.