不同温度条件下乙酸对长石溶蚀过程的实验研究

Experimental Study of Feldspar Dissolution by Acetic Acid at Different Burial Temperatures

本文报道了不同埋藏温压条件下乙酸对条纹长石溶蚀过程的实验研究。结果证明：１）在条纹长石溶蚀过程中，Ｋ、Ｎａ、Ａｌ优先释放，Ｓｉ是最后释放的元素。２）在相对低温的条件下，长石溶出主要元素的比例远远偏离其化学组成，在相对高温的条件下，则接近其化学组成。３）在条纹长石中．钠长石比钾长石更容易分解。４）温度升高对条纹长石中Ｓｉ的影响最大，其温度效应分别是Ｋ、Ａｌ、Ｎａ的９．２，８．６和５．４倍。５）不同温度区间Ｓｉ，Ａｌ的温度效应存在显著的差别，Ａｌ主要在小于９５℃区间释放，而Ｓｉ主要在大于９５℃区间释放，此时将有约２／３的Ｓｉ不能加入到高岭石中。因而在埋藏成岩过程中，自生ＳｉＯ２矿物沉淀造成的孔隙封堵作用主要发生在地温大于９５℃的埋深中。６）相对高温高压的实验中获得了蛋白石等自生ＳｉＯ２矿物的沉淀，进一步证明Ｓｉ主要是在高温区间释放的。

In order to evaluate the effect of organic acids on the dissolution of feldspar at different burial temperatures, perthite dissolution by acetic acid experiments were run at 65℃,20Mpa; 75℃,30MPa; 95℃, 30Mpa and 130℃, 30MPa. The experimental results are as follows:1) Postassium, sodium and aluminium were preferentially released,but silicon was last released in feldspar dissolution.2) Uner the conditions of relatively low temperature,the ratio of released canons was far from the chemical composition of dissolved feldspar, but when increasing temperature, it was gradually close to the composition.3) In perthite, albite is more easily to be decomposed than K-feldspar.4) Temperature effect of silicon is 5. 4, 8. 6 and 9. 2 times as large as sodium, aluminium andpotassium, respectively.5)Compared with aluminium, most silicon released at relatively high temperature (more than 95 ℃). It implies that the precipitation of authigenic SiO2 minerals which blocked up most of porosity occurred at the burial depth with geotemperature more than 95℃.