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钙碱性安山岩的主要发育地区是壳层厚度超过30Km的已演变形成的岛弧地区和大陆边缘区。在这两种情况下,安山岩既可能形成于含水的镁铁质下地壳的部分熔融,也可能来自于板下的含水镁铁质岩桨的分离结晶作用,直接的或间接的与沉降的大洋地壳及上覆于贝尼奥夫带的地幔楔的熔融作用相联系。然而不同于许多安山岩的是安山岩罕见以高压斑晶或包体的形式出现的深层位的历史证据,而可能受到浅层位作用的巨大影响。高压试验工作能够多方面的勾画出可能的源岩成分,以及深地壳和上地幔对岩浆母体形成钙碱性安山岩起作用的分离结晶作用。对于镁铁质源岩成分来说,结果是指向于两个主要模式:(1)8～12Kb下的角闪石模式;(2)超过25Kb的榴辉岩模式,以及12～25Kb范围内过渡的石榴石——角闪石模式。因此在8—12Kb压力下角闪石是含水镁铁质成分的物质中占主导地位的结晶相或残余相。所获得的液体具有钙碱性安山岩及相关岩石的主要元素特征。同样在超过25Kb时对干条件石英榴辉岩40～50％的熔融可能获得安山岩质液体,当水存在时较低程度的熔融可以产生英安岩及流纹岩的熔体,但是在干条件下较低程度的熔融形成粗面岩液体而不是安山质液体。痕量元素型式特别是REE可能带有这些模式的印记,但是较浅层位的结晶作用及其残余物对富集痕量元素的副矿物相(榍石、磷灰石等)来说,能够明显的改变痕量元素的浓度。控制钙碱性安山岩形成的两个主要因素是(1)经过含水的消减大洋地壳的脱水和熔融反应向地幔及深地壳中输送水,(2)在已演变成的岛弧及大陆边缘区存在着的增厚了的地壳,形成一个致密的相当于大约8～12Kb压力,促进了此层位的上涌岩浆的分离结晶作用。
The main development area of calc-alkaline andesite is the evolved island arc area and continental marginal area with shell thickness over 30 km. In either case, the andesite may either form part of the melt in the hydrous mafic lower crust, or separate from the underlying hydrous mafic rock, either directly or indirectly from the subsidence ocean The crust, and the mantle wedge overlying the Benioff belt. Unlike many andesite, however, is the historical evidence that andesite rarely occurs in the form of high-pressured plaques or inclusions and may be greatly affected by the action of shallow beds. High-pressure tests can outline possible source rock components in many aspects as well as the separation and crystallization of the deep crust and the upper mantle that contribute to the formation of calc-alkaline anorthites from magmatic matrices. For the mafic source rock component, the results point to two main modes: (1) amphibole mode at 8-12 Kb; (2) eclogite over 25 Kb and transition in the range of 12-25 Kb Garnet - amphibole pattern. Therefore, amphiboles are the dominant crystalline phase or residual phase in hydrous mafic material under 8-12 Kb pressure. The resulting liquid has the major elemental characteristics of calc-alkaline andesite and related rocks. Also, melting of 40-50% of the dry-condition quartz eclogites from above 25 Kb may yield andesite fluids that melt in the presence of water to produce melts of dacite and rhyolite, but under dry conditions Under the lower degree of melting to form a crude fluid instead of Anantara liquid. Trace element types, especially REEs, may have imprints of these patterns, but the crystallization of the shallower beds and their residues may be beneficial for the enrichment of trace elemental secondary mineral phases (gypsum, apatite, etc.) Significantly change the concentration of trace elements. The two main factors controlling the formation of calc-alkaline andesite are (1) the transport of water to the mantle and the deep crust through the dehydration and melting reactions of depleted oceanic crust, (2) the presence of arcs and continental margins that have evolved The thickening of the crust, forming a dense equivalent to about 8 ~ 12Kb pressure, and promote the formation of the upper part of the magma of the separation crystallization.