Granitoids with orbicular structure are very rare because of their unique orbicular structure.They stand as unique objects to study magma processes.When high-temperature magma contacted or mixed with low-temperature magma,due to their difference in viscosity and temperature,high interfacial tension leads the high-temperature magma to form orbicules in low-temperature magma.The temperature of orbicules decrease rapidly and result in high degrees of supercooling.Induced by exsolution of volatiles or other factors,the orbicules begin to crystallize and branched or feathery crystals are formed.The rapid crystallization in orbicules results in rapid change of local melt and the alternating crystallization of different minerals,forming dark and light rings.During this process,the crystallized minerals can exhibit branched or feathery structures.However,it is still unclear how viscosity and temperature control spheroidization,and how minerals crystallize after spheroidization,and how long the crystallization process lasts.These issues are waiting to be studied and revealed.
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