|Abstract: ||本實驗用合成玻璃包括Na2OAl2O3nSiO2，CaOAl2O3nSiO2，xNa2O(1-x)CaOAl2O3nSiO2及xNa2O(1-x)K2OAl2O36SiO2 等四系統的成分，加入鹼性溶液包括NaOH，KOH，Na2CO3，NH4OH，NaOH (+) NaCl，NaOH (+) KOH等，以蒸氣壓反應器，於110~210℃與蒸氣壓條件下合成沸石。合成之礦物用X光粉末繞射儀鑑定其種類，用電子顯微鏡觀察起始玻璃材料之溶蝕情形和礦物晶體生長之外形，並用電子微探儀和能量分散光譜儀分析合成礦物之化學成分。
本研究合成之沸石包括thomsonite，gismondine，amicite，garronite，gobbinsite，analcime，phillipsite，merlinoite，chabazite及mordenite等十種自然界出現的沸石，另外還合成一些人工沸石及長石類礦物等。實驗結果顯示，起始玻璃成分能決定合成沸石之SiO2/Al2O3比值與陽離子成分；溶液中的鈉和鉀含量也會直接影響沸石之陽離子成分，溶液中之碳酸根則會阻礙含鈣沸石的形成。此外，不同沸石各有其形成之溫度範圍，例如高溫相以thomsonite，garronite及analcime為代表，中高溫相以merlinoite 和mordenite為代表，中低溫相以gobbinsite，phillipsite及gismondine 為代表，低溫相則以chabazite和amicite為代表。
依據化學成分，可將所合成的沸石類分為低矽(SiO2/Al2O3 = 2~4)，中矽(SiO2/Al2O3 = 4~8)及高矽(SiO2/Al2O3 = 10)等三群。其中低矽沸石，包含SiO2/Al2O3比值接近2之thomsonite，gismondine與amicite和SiO2/Al2O3比值約3~4之gobbinsite與garronite；中矽沸石，包括analcime，phillipsite，merlinoite及 chabazite；高矽沸石只有mordenite。在陽離子成分方面，thomsonite，gismondine 及garronite皆以含鈣為主，並可含鈉，其中又以garronite的鈉含量變化較大；amicite則含鈉和鉀各半；gobbinsite和analcime以含鈉為主，少數可含有微量的鈣；phillipsite以含鈉和鉀為主，鈣則可有可無，成分變化相當大；merlinoite則以含鉀為主，並可含鈉；chabazite也以含鉀為主，偶爾含有鈉。
The experiments were carried out with synthetic glasses of the systems of Na2OAl2O3nSiO2, CaOAl2O3nSiO2, xNa2O(1-x)CaOAl2O3nSiO2 and xNa2O(1-x)K2OAl2O36SiO2 in alkaline solutions of NaOH, KOH, Na2CO3, NH4OH, NaOH (+) NaCl and NaOH (+) KOH under the conditions of temperatures from 110℃ to 210℃ and autogeneous pressures in the autoclaves. Synthetic products were examined by using an X-ray powder diffractometer, scanning electron microscope, electron microprobe and energy dispersive spectrometer.
The minerals synthesized include zeolites of natural occurrences, i.e., thomsonite, gismondine, amicite, garronite, gobbinsite, analcime, phillipsite, merlinoite, chabazite and mordenite; some synthetic zeolites, and feldspars. Chemical analyses indicate that compositions of synthetic zeolites are profoundly influenced by those of initial glasses, especially the SiO2/Al2O3 ratios and cations. Besides, Na+ and K+ relating with those in glasses and liquids media can influence zeolites synthesized as well, such as CO32- preventing the formation of Ca-zeolites. In addition, each zeolite is synthesized at different range of temperatures, for example, the high temperature phases include thomsonite, garronite and analcime; the medium-high temperature ones include merlinoite and mordenite; the medium-low temperature ones include gobbinsite, phillipsite and gismondine; and the low temperature ones include chabazite and amicite.
Based on chemical compositions, the synthetic zeolites can be grouped into low silica (SiO2/Al2O3 = 2~4), medium silica (SiO2/Al2O3 = 4~8) and high silica (SiO2/Al2O3 = 10) ones. The firs group includes thomsonite, gismondine, amicite, gobbinsite and garronite; second one includes analcime, phillipsite, merlinoite and chabazite; and mordenite is the last group. Thomsonite, gismondine and garronite are chiefly composed of Ca with certain amount of Na, and garronite generally has a wider Na content; amicite often has an equal amount of Na and K; gobbinsite and analcime are mainly composed of Na with a little amount of Ca; phillipsite is essentially composed of Na and K with various amount of Ca; merlinoite generally has higher K content than Na; chabazite is also mainly composed of K with less amount of Na.
The experimental results and natural observations suggest that thomsonite, gismondine and amicite can usually be found in ultrabasic and basic rocks; garronite and gobbinsite in basic to intermediate rocks; the wide-spread zeolites including analcime, phillipsite, merlinoite and chabazite in basic to acid rocks; merlinoite in high-potassium rocks; and mordenite in acid rocks. Besides, the Ca-zeolites including thomsonite, gismondine and garronite are favored in fresh water environments; and the sodic gobbinsite and amicite is suitable in saline lake and sea water. Moreover, analcime often occurs in the inner zone of saline lake deposits, while phillipsite in the marginal zone. Philllipsite is usually favored in deep-sea environments.