Origin Characteristics of Alluvial Diamonds in Brazil and Its Comparative Study

It has been an international challenge to determine diamond origin,especially of the alluvial diamonds,because they are usually mixed with other stuffs during transportation.In this paper,the essential characteristics and related research achievement of alluvial diamonds in Brazil are summarized concerning six perspectives,including geologic information,morphology and colour,internal structure,mineral inclusions,trace elements and C isotopic composition,which may offer a reference for origin of the alluvial diamonds worldwide.The study shows that the most diamonds in Brazil are similar to the other diamonds worldwide and it's hard to distinguish because they both largely contain peridotite.However,the diamonds from the Juina area and Machado River are distinguished in terms of their nitrogen content and aggregation(a large proportion of typeⅡ).And their internal structures,mineral inclusions and associations,forming environment are results of inner mantle,which are different from other deposits in Brazil.Meanwhile,the study on comparison among alluvial diamonds from different areas worldwide,shows that alluvial diamonds of different areas in different countries may have a certain difference in those perspective mentioned above,but it's still very difficult to discriminate diamond origins accurately with the existing data,so some in-depth and meticulous work need to be done.