【摘要】 <正> 滇西锡矿带主要的锡矿床都与花岗岩有成因关系。花岗岩岩石化学成分及其所计算出的各种岩化指数,对判别成锡与不成锡岩体提供了不少依据。然而,大量花岗岩岩石化学计算表明,每个岩体的岩化指数都具有一定的变化区间,有时差异颇大,甚至属于不同相图空间不同岩石化学系列的岩石;到达共结面(线)的残留固态成分百分比,有的>19％,有的<19％,即混合花岗岩与岩浆花岗岩也有过渡关系。实际上,很多岩体系多期次、多阶段形成的复式岩体,已为大家所公认。因此,以往工作中,一般都采用已习惯的简单的岩体、岩更多还原

【Abstract】 A large number of petrochemistry data indicate that people often get indistinct lithologic concept leading to the essential and non-essential confusion when using the average value of petrochemistry components,in general,for discriminating the rock masses（mainly composite rock masses）,rocks,rock belt and granites of different epoches.Although there are many methods in the count of petrochemical indexes,the differences of results obtained are small,various indexes all manifest the positive or negative correlation,to varying degrees,with the differential index（DI）.Under the premise for checking the representative nature of individual sample,through the differential index gained from calculation of C.I.P.W method combining with the Or-Ab-An-Q-H₂O phase diagram of H.G.F.Wenkler,the granite bodies can be discriminated. This paper emphatically discriminates whether the tin（tungsten）-forming process could occur in the granites based on introducing the calculating and drawing ways of DI index/phase diagram,the major petrochemistry characteristics and rock geneses of each rock belt,rocks and various epoch granites. A new conclusion can be gotten the tin-forming process doesn’t make much difference with the genetic types of rocks while it was a special manifestation when granites evolved to a high stage（87<DI<93）and towards an acidic direction（the sample point fall in the quartz space on phase diagram with the increase of DI value） because of the evolutional trend of granites with different geneses all closing to the low temperature eutectic points in phase diagram.It is,on the contrary,a disadvantage to tin-forming if magmatic evolution trend towards the alkaline direction duing late stage（the sample points fall in the space of alkali feldspars）.The concept on favourable tin-forming,therefore,for partial acidic/partial alkaline granites should be concretly handled.更多还原