The Ningbo iron meteorite fell near Ningbo, Chekiang province, on October 4,1975. 103 days later, γ-ray spectrum of the meteorite, was undestructively measured
109 isotopic ages have been determined and collected in the recentten years, Most of them belong to Yenshanian, within which an early period (140--180m.y.) and
In the present paper the mode of occurence of niobium and tantalum in cassiterite has been studied, suggesting that the two elements are present in the form of