菲律宾迪纳加特岛汇洋镍铬矿区铬铁矿成矿地质特征

菲律宾迪纳加特岛汇洋镍铬矿区发育板块碰撞成因的蛇绿岩,主要岩性为纯橄岩和方辉橄榄岩,与铬铁矿化关系密切,在纯橄岩和方辉橄榄岩的过渡带中铬铁矿化较为集中,铬铁矿多呈薄层块状或浸染状与围岩岩性条带呈"互层状"产出,块状、浸染状的铬铁矿重复出现;矿区内原生铬铁矿化非常普遍,虽然未构成原生铬铁矿体,但为次生红土型铬铁矿的成矿提供了丰富的物质来源。矿区内第四系中赋存有残坡积红土型铬铁砂矿,并与同类型镍矿共生;铁质红土层是最佳的含矿层位,松散状红土层次之;铬铁矿体呈层状、似层状,有3个铬铁砂矿化区,矿体厚度5~7m,铬铁矿品位w(Cr2O3)=2.0%~4.1%。

Metallogenic characteristics of chromium deposits in Huiyang Ni-Cr property at Dinagat island, Philippines

The plate-collision ophiolite occurs in Huiyang Ni-Cr property at Dinagat island,Philippines. The ophiolit is mainly composed of dunite and harzburgite and the latter are closely related to Cr mineralization.At the transition zone between the dunite and harzburgite Cr mineralization is relatively concentrated.Disseminated and massive chromite is nterlayered with the host rock.Primary Cr mineralization is widely spread here.No primary Cr deposit can be located within the mineralization.However,the mineralization provides abundant source material for the lateritic Cr deposits here.In the property residual Cr placers occurs in the Tertiary sediment together with Ni placers.Ferrous laterite is the optimum horizon of Cr placer and the next is loose laterite.The Cr placer is layered or layeroid.There are 3mining areas with layered Cr placer.The ore body is 5-7mthick with grade of Cr2O3=2.0%-4.1%.