Alkaline Intrusive Complexes are a fascinating subject in the field of geology, offering a rich source of minerals and providing insights into the Earth’s mantle processes.

Introduction

Alkaline rocks form an expansive category of igneous rocks. They are generally deficient in SiO2 relative to Na2O, K2O, and CaO. Two of the most important subclasses of alkaline rocks with respect to Rare Earth Element (REE) deposits are carbonatites and peralkaline rocks.

Alkaline Intrusion-Related Mineral System

Alkaline intrusion-related mineral systems are quite diverse, ranging from diamond, through REE-P-U, to Ni-Cu-PGE and vermiculite deposits. These deposits contain a large number of critical commodities, including REE, PGE, Ni, Th, and Zr.

Alkaline magmas and carbonatites are thought to originate as generally low degree partial melts of metasomatised or crustally contaminated mantle. The parental carbonatite magmas originate by the separation of an immiscible carbonate liquid phase from a CO2-saturated nephelinite or phonolite magma.

Geological Setting

Alkaline igneous rocks are found in a large range of geological settings, including continental rift valleys, intraplate magmatic provinces with uncertain tectonic settings, and destructive plate boundaries. Carbonatites occur in continental shields and are commonly related spatially to fault lineaments such as in rift systems.

Economic Importance

Carbonatite and alkaline intrusive complexes, as well as their weathering products, are the primary sources of REEs. A wide variety of other commodities have been exploited from carbonatites and alkaline igneous rocks including niobium, phosphate, titanium, vermiculite, barite, fluorite, copper, calcite, and zirconium.

Conclusion

Alkaline Intrusive Complexes play a significant role in our understanding of the Earth’s mantle processes and the formation of mineral deposits. Their study is crucial for the exploration and extraction of critical commodities that are essential for modern technology.

References

  1. Carbonatite and Alkaline Intrusion-Related Rare Earth Element Deposits
  2. Alkaline intrusion-related mineral system – Geoscience Australia
  3. USGS Scientific Investigations Report 2010–5070–J: A Deposit Model for …