Experimental Investigation of the Depth of Origin of the Alpe Arami Peridotite Massif, Switzerland

对瑞士南部阿尔卑阿拉米橄榄岩地块的新鲜石榴石二辉橄榄岩进行了9628342次绿色初步观测和分析。新的数据表明，历史上的压力比辉石温压计计算出的4-5 Gpa要高得多。老一代橄榄石有大量定向氧化物包裹体，几乎可以肯定是出溶的产物。困难的是，三价和四价阳离子的隐含溶解度比之前报道的橄榄石在任何环境中的溶解度都要大得多。在6和14 Gpa，1700(K)下的初步实验证实，随着压力的增加，二氧化钛在橄榄石中的溶解度大大增加，在高压多晶型橄榄石中的溶解度更高。这个项目包括在非常高的温度和压力下进行一系列实验，以描绘出橄榄石在什么条件下(如果有的话)可以溶解观察到的钛、铝和铬，以及在什么条件下可以从固溶体中析出观察到的结构、形貌和拓扑结构。三个具体的可检验的假设将被检验。(1)FeTiO_3棒是出溶形成的。(2)它们的丰度可能代表了在任何情况下都不能溶解在橄榄石中的二氧化钛，因此它们可能反映了一些预先存在的相。(3)如果在钛铁矿稳定区发生出溶，钛铁矿将直接以片状析出，根本不会形成(可能的)亚稳态氧化物棒。

9628342 Green Preliminary observations and analyses have been made on the fresh garnet lherzolite of the Alpe Arami peridotite massif in southern Switzerland. The new data suggest a history involving much higher pressure than the 4-5 GPa calculated from pyroxene thermobarometry. The older generation of olivine has large numbers of oriented oxide inclusions that are almost certainly products of exsolution. The difficulty is that the implied solubility of trivalent and tetravalent cations is very much greater than previously reported for olivine from any environment. Preliminary experiments at 6 and 14 GPa, 1700(K, confirm that the solubility of TiO2 in olivine increases greatly with pressure, and that it is significantly higher still in the high pressure polymorph of olivine. This project consists of a series of experiments at very high temperature and pressure to delineate under what conditions, if any, olivine can dissolve the observed amounts of Ti, Al and Cr, and under what conditions the observed structures, morphologies and topotaxies can be precipitated from solid solution. Three specific testable hypotheses will be examined. (1) The FeTiO3 rods originated by exsolution. (2) Their abundance probably represents more TiO2 than can dissolve in olivine under any circumstances, hence they may reflect some pre-existing phase. (3) If exsolution takes place in the ilmenite stability field, ilmenite would have precipitated directly as platelets and the (presumable) metastable oxide rods would not have formed at all.