Genetical research on alkali rocks acoompanied with skarn

本文对冈山县福冈和广岛市钏路地区高温交代产物碱岩伴矽卡岩的成因进行了探讨。碱岩赋存状态：在两区灰岩中赋存较多的石英二长岩脉。滑石矿物原生形成于岩脉两侧，呈（石英二长岩）-（辉长岩带）-（闪长岩带）-（结晶灰岩）带状排列。碱岩产于石英二长岩与辉长岩的交界地带，常与花岗岩和维苏岩亚带伴生。矽卡岩形成过程中元素的转移：元素由石英二长岩提供。每个元素的移动距离与其离子半径有关。像Si这样的小离子可以移动20米，而像Na这样的大离子则不能移动。很明显，这些元素是通过扩散机制移动的。碱性岩化学特征：Al_2O_3含量与石英二长岩基本相同。假设铝（g/100cm^3）恒定，石英二长岩碱岩变化的增益（+）和损失（-）如下：SiO_2: -36 - 60, Na_2O: 2、K_2O: 5, FeO说^ *:-3.9 - -20.5,分别以:3 - 17,曹:9-30g / 100厘米^ 3,拉:-3.5 - -2.2,Ce: 5.1——2.0,公关:-0.4 - -0.2。Nd: -0.5-0.5, Ba: 87, Li: 33, Sr: 69, V: 66, Zn: 81, Zr: 28mg/100cm^ 3mg /100cm^3.4。碱岩的形成：从石英二长岩中浸出大量二氧化硅，平均52g/100cm^3，并与辉长岩带反应。因此，石英二长岩岩浆缺乏二氧化硅。碱岩很可能是由石英二长岩脱硅形成的。

The present study aims at clayfing the genesis of alkali rocks accompanied with skarns, which are formed as high-temperature metasomatic products at Fuka, Okayama Prefecture and Kushiro, Hiroshima Prefecture.1. Occurrence of alkali rocks : In the two districts, many quartz monzonite dikes occur in limestones. Skam minerals are primarity formed on both side of the dikes, and show a zonal arrangement : (quartz monzonite) - (gehlenite zone) - (spurrte zone) - (crystaline limestone). The alkali rocks occur along the boundary between quartz monzonite and gehlenite zone, and are always accompained with granet and vesuvianite sub-zones.2. Transfer of elements during the skarn formation : The elements are supplied from quartz monzonite. The distance of movement of each elment is related to its ionic radii. The small ions as Si move up to 20 meters, and the lager ions as Na moveless. It is clear that the elements are moved by the diffusion mechanism.3. Chemical features of alkali rocks : The Al_2O_3 contents are almost the same as those of quartz monzonite. Gains (+) and losses (-) during the change in alkali rocks from quartz monzonite, assuming constant aluminum (g/100cm^3) , are as follows ; SiO_2 : -36--60, Na_2O : -2, K_2O : -5, FeO^* : -3.9-20.5, MgO : 3-17, CaO : 9-30g/100cm^3, La : -3.5-2.2, Ce : 5.1--2.0, Pr : -0.4-0.2.Nd : -0.5-0.5, Ba : 87, Li : 33, Sr : 69, V : 66, Zn : 81, Zr : 28mg/100cm^3 mg/100cm^3.4. Formation of alkali rocks : Much silica, 52g/100cm^3 on an average, leached from Quartz monzonite, and reacted to the gehlenite zone. As a consequence, quartz monzonite magma was deficient in silica. It is very likely that the alkali rocks was formed by desilication of quartz monzonite.