Abstract:
Kimberlite in Shizhuang area of southern Henan Province lies in the south of North China plate and in the north of Luanchuan-Minggang deep-large fault zone.Indicative minerals of diamond, such as spinel, are found in Kimberley rocks.The indicative minerals of spinel and other diamonds have been obtained from kimberlite in Shizhuang area by artificial heavy sand identification.The chemical composition of spinel was studied by means of electron microprobe analysis in this paper.The results show that the spinel group minerals in kimberlite in Shizhuang area are mainly composed of magnesia chromite(MgCr
2O
4)-chromite(FeCr
2O
4)-magnesia spinel(MgAl
2O
4)-spinel(FeAl
2O
4), in which magnesia chromite(Fe, Mg)Cr
2O
4 is dominant.The content of Cr
2O
3 and Al
2O
3 in chromite varies widely, MgO content is high(5.57%~15.8%), TiO
2 content is low, and there exists a chromite with low titanium, rich magnesium and high aluminum content(S5 type).Among the cations of chromite, Mg
2+ > Fe
2+, while Cr
3+ and Al
3+, Mg
2+ and Fe
2+ have experienced extensive substitution.A preliminary analysis shows that chromite in kimberlite in Shizhuang area is mantle xenocryst, while in situ mantle is peridotite.The chemical characteristics of spinel minerals show that the kimberlite in Shizhuang area has the capability of carrying diamond, which is of great significance for the exploration of kimberlite type diamond deposits.