巖漿成因外文翻譯-資料下載頁(yè)
2025-05-12 03:40本頁(yè)面
【導(dǎo)讀】基于現(xiàn)有的科學(xué)證據(jù)顯示，地球的地殼和地幔主要由堅(jiān)硬的巖石組成。體狀態(tài)，這種材料是非常密集并保持在地球內(nèi)部深處的。在近地表環(huán)境，花崗巖在800℃左右的。溫度下開(kāi)始融化，而玄武巖必須達(dá)到1000℃以上。一個(gè)重要的差異存在于單一物質(zhì)和化合物。之間，例如冰和幾種不同的礦物混合成的火成巖的熔點(diǎn)?；鸪蓭r在幾百度的溫度范圍內(nèi)熔融。巖石被加熱時(shí)，第一個(gè)形成液體的包含一個(gè)比原巖百分。如果繼續(xù)熔化，該熔體將穩(wěn)步接近從巖石的整體組成。這個(gè)過(guò)程被稱(chēng)為部分熔融，不全部生成巖漿。部分熔融的結(jié)果明顯比母巖熔融產(chǎn)生的二氧化硅含量高。來(lái)源之一被認(rèn)為是集中在上地幔和地殼的放射性元素衰變過(guò)程。被認(rèn)為是平均上升每公里增加20℃到30℃。在該地區(qū)，包括黃石公園。這兩個(gè)過(guò)程都被認(rèn)為是在巖漿的形。然而，由于干燥的玄武巖巖漿向上移動(dòng)，圍壓的穩(wěn)步減少，進(jìn)一步降低了熔點(diǎn)。玄武質(zhì)巖漿出現(xiàn)快速上升足以使他們進(jìn)入較冷的環(huán)境中的熱損失的熔點(diǎn)下降所抵消。
【正文】 reduces the melting point. Basaltic magmas appear to ascend rapidly enough so that as they enter cooler environments the heat loss is offset by a drop in the melting point. Consequently, large outpourings of basaltic magmas are mon on the earth’s surface. Conversely, granitic magmas are thought to be generated by partial melting of waterrich rocks that were subjected to increased temperature. As a wet granitic melt rises, the confining pressure decreases, which in turn reduces the effect of water on lowering the melting temperature. Further, granitic melts are high’in silica and thus more viscous than basaltic melts. Thus, in contrast to basaltic magmas that produce vast outpourings of lava, most granitic magmas lose their mobility before reaching the surface and therefore tend to produce large intrusive features such as batholiths. On those occasions when silica rich magmas reach the surface, explosive pyroclastic flows,such as those that produced the Yellowstone Plateau, are the rule. Even though most magma is thought to be generated by partial melting, once formed the position of a magma body can change dramatically with time. For example, as a magma body migrates upward, it may incorporate some of the surrounding country rock. As the country rock is assimilated, the position of the magma is altered. Further, recall from our discussion of Bowen’s reaction series that during solidification, magma often undergoes fractional crystallization. This produces a magma quite unlike the parent material. These processes account, at least in part, 5 for the fact that a single volcano can extrude lavas with a wide range of chemical positions.
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