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样品来自南沙地块北缘、洋陆过渡带附近2个拖网站位,主要为代表陆壳基底的中-酸性侵入岩,如花岗闪长岩(中性组)和二长花岗岩(酸性组)等。分析了这些中-酸性侵入岩的长石、黑云母和角闪石等矿物的主量元素成分。中性组的斜长石的牌号(An为13～38)明显高于酸性组的斜长石的牌号(An值为9～12),岩石主要组成部分的斜长石成分与岩石类型一致。两组岩石的黑云母均为富镁黑云母,黑云母成分反映其岩浆物质来源为幔源或壳幔混源,且酸性组的黑云母成分反映其寄主岩石受到地幔物质的影响要大于中性组,角闪石只出现在中性岩石内,为壳幔混合成因,反映其寄主岩石为典型的I型花岗岩。矿物共生组合温压条件计算表明,中性组岩石的结晶温度和深度分别为544～630℃(平均为573℃)和18～19 km,而酸性组岩石的结晶温度和深度总体上都低于中性组岩石,分别为416～538℃(平均为494℃)和9～10 km。本研究所揭示的矿物化学特征与所计算的温压条件为基于全岩元素地球化学特征提出的岩石成因模型提供证据。
The samples are from two trawl sites near the northern edge of Nansha block and the Yanglu transitional zone, and are mainly medium-acidic intrusive rocks that represent continental basement such as granodiorite (neutral group) and monzogranite (acidic group) Wait. The major elements of these minerals, such as feldspar, biotite and amphibole, were analyzed. In the neutral group, plagioclase grades (An = 13-38) were significantly higher than those of acidic group plagioclase (An = 9-12). The major components of plagioclase were consistent with the rock types. The biotite in both rocks are magnesium-rich biotite. The biotite component reflects that the source of magma is the mantle source or crust-mantle mixed source, and the biotite composition of acidic group reflects that the host rock is more affected by the mantle material than neutral In the group, amphibole only appears in the neutral rock, which is the genesis of crust-mantle mixing, reflecting that the host rock is a typical type I granite. Calculations of the synergistic combination of temperature and pressure show that the crystallization temperature and depth of the neutral rocks are respectively 544 ~ 630 ℃ (average 573 ℃) and 18 ~ 19 km, while the crystallization temperature and depth of acidic rocks are generally lower than Neutral rocks are 416-538 ° C (494 ° C on average) and 9-10 km respectively. The mineralogical characteristics and the calculated temperature and pressure conditions revealed in this study provide evidence for the rock genetic model based on the geochemistry of the whole rock element.