主量元素图解
• 在主量元素图解中最常用的元素有Al2O3、MgO、CaO、 TiO2、SiO2等不活泼元素，在部分图解中也采用FeO*、 Na2O、K2O等相对活泼的元素。 • 与微量元素相比主量元素判别图解具有以下优点： (1)由于主量元素分析方法相对简单廉价，因此数据资料容易 获得。 (2)由于主量元素在岩石中的含量较高，所以分析误差相对较 小，由此产生的判别误差也减小．虽然在很多情况下，主 量元素在玄武岩的蚀变或变质作用过程中发生的活化并不 影响图解的判别功能，但是由于大部分主量元素在玄武岩 的蚀变或变质作用过程中都很活泼，因而限制了主量元素 在玄武岩构造环境判别图解中的使用。
0 -1.2
0.1
0.2
0.3
0.4
0.5
-1.7
-1.6
-1.5
-1.4
-1.3
-1.2
F1
SHO
-2.2
F2
-1.3
-2.3
-1.4
WPB (OIB+CON) CAB+LKT
Hale Waihona Puke LKT-2.4-1.5
OFB
OFB
-1.6
-2.5
CAB
SHO
-1.7
F2
-2.6
F3
2 构造环境描述 首先对图解中各种构造环境的构造含义作个说明： OFB(ocean floor basalts)：是指喷发于扩张板块边缘的玄武岩，它既可以是大 洋内部（洋中脊），也可以是岛弧后的小洋盆。 LKT(low-potassium tholeiites,Island arc tholeiites)：喷发于会聚板块边缘大洋地 壳的低钾拉斑玄武岩和岛弧拉斑玄武岩，经常喷发于深海槽附近。 CAB(calc-alkali basalts)：喷发于会聚板块边缘的大陆地壳及深海槽后大洋地壳 环境的钙碱性玄武岩。 SHO(shoshonites)：喷发于会聚板块边缘的橄榄粗安岩，它既可以是距深海槽 很远的成熟弧，也可以是俯冲后的造山期后环境。 OIB(ocean island basalts)：喷发于洋盆内洋岛，大部分在板内环境。 CON(continental Basalts)：喷发于大陆地壳，大部分在板内的大陆裂谷。
F3
F1-F2和F 2-F3图解是由J. A. Pearce于1976 年创立的，它们主要用于区分六种不同构 造环境下形成的玄武岩。
1 图解功能 F1-F2图解可以区分OFB、LKT+CAB、 SHO、WPB(包括 OIB和CON)等几种不同构造环境的玄武岩。 F2-F3图解则可以区分OFB、LKT、CAB、SHO等四种构 造环境。
常用玄武岩构造环境判别图解
•主量元素图解 •微量元素图解 •与残留辉石有关的判别图解
参 考 文 献
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