摘要
与形成的不同模式， charnockitic 岩石的四个不同变化从 Mesoproterozoic 出生的带被描述，新 C 同位素数据介绍了。在很多石场和河节的优秀沿海的暴露为观察 charnockitic 地关系使出生的带的这部分成为一个好地点。而 charnockites 的开始和条款 charnockite 的使用上有许多争论，相对在 granitoid 岩石中的黑云母的 orthopyroxene 的稳定是低 aH2O 的功能，这通常被认出(? 瀠獯 ? 慭浧瑡捩 ????? 敲牣獹慴汬獩瑡潩吗？
Four different varieties of charnockitic rocks, with different modes of formation, from the Mesoproterozoic Natal belt are described and new C isotope data presented. Excellent coastal exposures in a number of quarries and river sections make this part of the Natal belt a good location for observing charnockitic field relationships. Whereas there has been much debate on genesis of charnockites and the use of the term charnockite, it is generally recognized that the stabilization of orthopyroxene relative to biotite in granitoid rocks is a function of low aH2O （-- high CO2）, high temperature, and composition （especially Fe/（Fe ＋Mg））. From the Natal belt exposures, it is evident that syn-emplacement, magmatic crystallization of charnockite can arise from mantle-derived differentiated melts that are inherently hot and dry （as in the Oribi Gorge granites and Munster enderbite）, as well as from wet granitic melts that have been affected through interaction with dry country rock to produce localized charnockitic marginal facies in plutons （as in the Portobello Granite）. Two varieties of post-emplacement sub-solidus charnock- ites are also evident. These include charnockitic aureoles developed in leucocratic, biotite, garnet granite adjacent to cross-cutting enderbitic veins that are attributed to metamorphic-metasomatic processes （as in the Nicholson＇s Point granite, a part of the Margate Granite Suite）, as well as nebulous, patchy charnocki- tic veins in the Margate Granite that are attributed to anatectic metamorphic processes under low-aH2O fluid conditions during a metamorphic event. These varieties of charnockite show that the required physical conditions of their genesis can be achieved through a number of geological processes, providing some important implications for the classification of charnockites, and for the interpretation of charnock- ite genesis in areas where poor exposure obscures field relationships.
