①化学成分。主要由氧、硅、铝、铁、钙、钠、钾、镁、钛、锰、氢、磷等12种元素组成。它们被称为造岩元素，约占火成岩总重量的99%以上，尤以氧最多，占总重量的46%以上。其余所有元素的重量总和还不到1%。它们常用氧化物百分数表示（表1）。SiO2是岩浆岩中最重要的一种氧化物，其含量是岩石分类的一个主要参数。如SiO2含量大于65%的火成岩称酸性岩，含量52%～65%者为中性岩，45%～52%者为基性岩，小于45%者为超基性岩。K2O+Na2O重量百分数之和称为全碱含量，也是岩石分类的一个重要参数。除12种主要元素外，火成岩中还含有许多种微量元素，如Au、Ag、As、B、Ba、Be、Cu、Pb、Zn、F、Cl、S、Ce、Li等。
②矿物成分。常见的矿物有20多种，通称造岩矿物（表2）。依其化学成分可分为两类。硅铝矿物，SiO2与Al2O3含量高，不含FeO、MgO，如石英类、长石类和似长石类。这类矿物颜色浅，故也称浅色或淡色矿物。铁镁矿物，FeO和MgO的含量较高，SiO2含量较低。如橄榄石类、辉石类、角闪石类及黑云母类等。这类矿物的颜色较深，故又称深色或暗色矿物。硅铝矿物和铁镁矿物在火成岩中的比例是岩石鉴定和分类的重要标志之一。火成岩的矿物成分和化学成分取决于岩浆来源，也取决于岩浆演化成岩的总过程。如来自幔源的岩浆富含铁、镁、铬等元素，形成的岩石以铁镁矿物为主，而来自壳源的岩浆富含硅铝元素，形成的岩石以硅铝矿物为主，花岗质岩浆在演化过程中与碳酸盐岩接触交代形成的矽卡岩以含钙矿物为主等。
Chemical composition. Mainly by oxygen, silicon, aluminum, iron, calcium, sodium, potassium, magnesium, titanium, manganese, hydrogen, phosphorus and other 12 elements. They are known as rock forming elements, accounting for more than 99% of the total weight of igneous rocks, especially the most oxygen, which accounts for more than 46% of the total weight of the total weight. The total weight of all the remaining elements is less than 1%. They are expressed in terms of the percentage of oxides (Table 1). SiO2 is one of the most important oxides in magmatic rocks, and its content is one of the main parameters of rock classification. Such as SiO2 content greater than 65% of the igneous rock that acidic rocks, content of 52% ~ 65% who neutral rocks, 45% to 52% of those mafic, less than 45% who ultrabasic rocks. K2O+Na2O weight percentage and the total alkali content, is also an important parameter of rock classification. In addition to the 12 major elements, the igneous rock also contains many kinds of trace elements, such as Au, Ag, As, B, Ba, Be, Cu, Pb, Zn, F, Cl, S,, Ce, Li, etc..
②矿物成分。常见的矿物有20多种，通称造岩矿物（表2）。依其化学成分可分为两类。硅铝矿物，SiO2与Al2O3含量高，不含FeO、MgO，如石英类、长石类和似长石类。这类矿物颜色浅，故也称浅色或淡色矿物。铁镁矿物，FeO和MgO的含量较高，SiO2含量较低。如橄榄石类、辉石类、角闪石类及黑云母类等。这类矿物的颜色较深，故又称深色或暗色矿物。硅铝矿物和铁镁矿物在火成岩中的比例是岩石鉴定和分类的重要标志之一。火成岩的矿物成分和化学成分取决于岩浆来源，也取决于岩浆演化成岩的总过程。如来自幔源的岩浆富含铁、镁、铬等元素，形成的岩石以铁镁矿物为主，而来自壳源的岩浆富含硅铝元素，形成的岩石以硅铝矿物为主，花岗质岩浆在演化过程中与碳酸盐岩接触交代形成的矽卡岩以含钙矿物为主等。
Mineral composition. There are 20 kinds of common minerals, commonly known as rock forming minerals (Table 2). According to their chemical composition can be divided into two categories. Silicon aluminum minerals, SiO2 and Al2O3 content is high, does not contain FeO, MgO, such as quartz, feldspar and feldspar. This kind of mineral light color, so called light or light minerals. The content of FeO and MgO is higher, and the content of SiO2 is lower than that of Fe and Mg. As such, olivine pyroxene, hornblende and biotite type etc.. This type of mineral is darker, it is also called the dark or dark minerals. The proportion of silicon aluminum minerals and iron and magnesium minerals in igneous rocks is one of the important signs of the identification and classification of rocks. The mineral composition and chemical composition of igneous rocks depend on the source of magma, and also depends on the total process of magmatic evolution. Buddha from the mantle source magma is rich in iron, magnesium, chromium and other elements, the rock formation in ferromagnesian minerals mainly, and from crust derived magma rich in silicon and aluminum elements, rock formation in aluminum silicon minerals, skarn granitic magma formed in the evolution process and carbonate rock contact metasomatic skarn minerals containing calcium.
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