anorthite diabase
3.According to the geological characteristics, the mafic dykes in Huangling area mainly include diabase and diabase-prophyrite, with nearly NEE trend and NNW trend.
4.This zone consists of basalt, diabase and other basic intrusive rock, and the isotopic age is between 259 Ma and 292 Ma.
5.The zircon, from the diabase-gabbros, U-Pb age of 402 Ma shows that the basic swarms were intruded in the middle Palaeozoic.
6.Cataclactic and mylonitic texture as well as massive structure can be found in the rim of diabase dikes and veins which have been strongly altered and mainly consist of albite, amphibole, chlorite, epidote and calcite with a little residual plagioclase and pyroxene.
7.The geo-barometric formulation is p (bar) = 2237.9 + 12.005T + 1.73T、LnK. The mineral thermodynamics data have been taken from the data base of Dexter Perkins components and anorthite in plagioclase and garnet have been modelled after wood and Banno (1973), Newton (1983) and Saxana (1984) respectively.
8.According to the isotopic chronological determination, the Rb Sr isochron age of the diabase whole rock within the fault zone is (100±5.9)Ma, the 40 Ar/ 39 Ar plateau age of the augite is 105Ma.
9.Through opencut mining of Cihai hidden iron ore deposit in recent years, it is found that there are multiperiodic diabase walls penetrated the steeply north-inclining iron ore bodies in different directions in early postmineral period so as to destroy the Integrity of the iron ore bodies and divide them into many small south-inclining bodies.
10.Based on an analysis of geochemical characteristics of rocks and trace elements as well as rare earth elements, this paper holds that they are products of crystallization differentiation of the same magma, that the major ore resource of this area is copper, and that gabbro-diabase is the main ore-bearing horizon.
