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岩浆岩主要造岩矿物野外鉴定
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1、石英

1, quartz

石英是花岗岩类岩石的主要矿物。其形态除在文像花岗岩中呈蠕虫状外和在浅成岩和喷出岩中可呈六方双锥的斑晶外,在绝大多数情况下呈它形粒状的晶体。颜色从无色到烟灰色。晶面呈玻璃光泽,但常见到的是断口面上的油脂光泽。与钾长石、酸性斜长石、黑云母共生。抗风化能力强,在岩石风化面上常呈现出明显的凸起。与长石的区别在于无解理,看不到双晶,油脂光泽和无风化产物。

Quartz is the main mineral of granite. The morphology of the granite like except in Vermicular and in hypabyssal rocks and lavas were spotted six party crystal double cone, it is shaped granular crystals in most cases. Color from colorless to smoky gray. The crystal is shiny glass, but is common to the oil sheen on the surface of fracture. Symbiosis with acidic potassium feldspar, plagioclase, biotite. The weathering resistance is strong, and the rock weathering surface often shows obvious uplift. No cleavage is and feldspar difference, can not see the twin, and no oil sheen weathering products.

2、钾长石

2, potash feldspar

钾长石包括正长石、微斜长石、条纹长石、透长石等。产于侵入岩中的主要是正长石和微斜长石,在浅成岩和喷出岩中可以是透长石。条纹长石是正长石或微斜长石与钠长石交生的产物,其中正长石或微斜长石多于钠长石。颜色是鉴别钾长石的一个重要标志。钾长石通常是肉红色的,但也有呈紫红色、白色、灰白色,甚至灰黑色。钾长石在风化过程中颜色会发生改变,肉红色可变成灰白色,灰白色也可变为肉红色。而且酸性斜长石也常呈肉红色。因此,颜色不能作为钾长石鉴定时的特征性标志。产于深成岩中的钾长石、微斜长石常呈它形粒状晶体。当钾长石在斑状、似斑状岩石中构成斑晶时,常呈板状、板柱状自形的晶体。野外鉴定长石时要特别注意双晶的观察。当旋转标本,发现长石解理面上出现一半反光,一半不反光时,此即为卡斯巴双晶;当出现相间反光时即为聚片双晶。钾长石常具卡斯巴双晶,而斜长石常具聚片双晶。这才是区别钾长石和斜长石重要的标志。如果在大的钾长石晶体上,见有根须状的细脉,而且细脉的颜色又较浅,则为条纹长石。钾长石风化时,常生成白色的土状高岭石。

Potassium feldspar includes orthoclase and microcline and perthite, sanidine etc.. Produced in the intrusive rocks are mainly of orthoclase and microcline in hypabyssal rocks and lavas can be sanidine. Perthite is orthoclase or microcline and albite over the product, which is more than orthoclase or microcline albite. Color is an important indicator to identify potash feldspar. Potassium feldspar is usually red meat, but there was purple, white, gray, or black. In the course of weathering, the color of potash feldspar will change, and the red color of meat can be turned into grey and white. But also often acid plagioclase was red meat. Therefore, the color can not be used as a characteristic marker of potash feldspar. In the plutonic rocks in K-feldspar and microcline are usually anhedral granular crystal. When the potassium feldspar phenocrysts in porphyritic porphyritic rocks, like in form, often with a plate, plate columnar euhedral crystals. Field evaluation of feldspar should pay special attention to twin observation. When the rotation were found on the cleavage plane appear half reflecting feldspar, half are not reflective, this is when a white reflective Carlsbad twin; is polysynthetic twin. Often with potassium feldspar and plagioclase Carlsbad twin, often with polysynthetic twin. This is a sign of the difference of potassium feldspar and plagioclase is the most important. If the large K-feldspar crystals, see roots like veins and veinlets, color is shallow, is perthitic. During the weathering of potassium feldspar, the white clay kaolinite is often formed.

3、斜长石

3, Xie Changshi

斜长石广泛出现在各类岩浆岩中。斜长石的种类和含量对于岩浆岩的分类和鉴定至关重要。斜长石可呈不同的色调,一般基性斜长石颜色较深,为深灰色到灰白色;酸性斜长石颜色较浅,可呈灰白、肉红色。基性斜长石由于遭受钠黝帘石化,其蚀变产物常带绿色色调;而酸性斜长石易绢云母化,其风化产物多呈灰白色。在基性浅成岩或喷出岩(如辉绿岩、玄武岩)中,由于斜长石颜色较深且结晶细小,因此很难辩认。这时,可采集半风化的标本观察,由于斜长石风化后颜色变浅,而与暗色矿物易于区别。聚片双晶是斜长石的重要鉴定标志。将标本向不同方向旋转,直到用野外或放大镜看到晶面或解理面上出现一组平行的明暗相间的直线或折线,这就是双晶纹。一般情况下,酸性斜长石双晶纹密集且平直,而基性斜长石的双晶纹较稀且不够平直。 Plagioclase widely appear in all kinds of magmatite in. The type and content of plagioclase is crucial for the classification and identification of magmatite. Can show different shades of plagioclase, generally the mafic color is deep, dark gray to gray white; acidic plagioclase is lighter in color, gray, red meat. The mafic due to sodium zoisitization, its alteration products often with green color; and easy acid plagioclase sericite, the weathering products mostly white. On the base of rocks or volcanic rocks (such as diabase, Xuan Wuyan), because the color is deep and fine crystallization of plagioclase, so it is difficult to identify. This observation can be collected semi weathered specimens, due to weathering of plagioclase pale, and can be easily distinguished from dark minerals. Polysynthetic twinning is an important sign of plagioclase identification. The specimen with different direction, with the field or a magnifying glass to see a group of parallel dark and straight line or a line or plane appears on the cleavage plane until it is twin. In general, acid plagioclase twin dense and flat, while the mafic twin is thin and not straight.

4、普通角闪石

4, hornblende

普通角闪石是闪长岩、正长岩中常出现的矿物,也常出现在花岗岩中。普通角闪石多呈黑色、暗绿色,有时为褐色。在侵入岩中的角闪石多呈长柱状晶体,但在某些花岗岩、花岗闪长岩中,角闪石的一向伸长的结晶习性并不显著。角闪石在解理、光泽、硬度上与辉石相近,因此易与辉石混淆。野外鉴定时可根据解理夹角相区分。具体做法是:在照射光下看到一组反光良好的阶梯状反光面(解理面),然后在眼睛的注视下转动标本,直到观察到第二组反光面,其旋转角度就是解理夹角。估计这个角度,若近90度,即为辉石;若为较明显的锐角或钝角,则为角闪石。另外,普通角闪石常与石英、钾长石、黑云母共生;而辉石则常与橄榄石、基性斜长石共生。在花岗岩中,普通角闪石与黑云母有时也会混淆,其区别在于,角闪石硬度大于小刀,用小刀刻划只能得到碎屑状颗粒,解理面上为玻璃光泽;而黑云母硬度小于小刀,用小刀可挑成薄片,解理面具珍珠光泽。另外,遭受风化后的角闪石常具绿色色调,而黑云母风化后常具褐色色调。

Hornblende is often diorite, syenite in minerals, often appear in granite. Hornblende is black, dark green, sometimes brown. Amphibole in the intrusive rock in a long columnar crystal, but in some granite, granodiorite, hornblende has elongated crystal habit is not significant. In amphibole cleavage, gloss and hardness and therefore easy to pyroxene similar confusion and pyroxene. The field identification according to the extinction angle distinguish. The specific approach is: to see a group of reflecting good ladder reflector in the light irradiation (cleavage), and then rotate the specimen in the eyes, until the observed second groups reflecting surface, the rotation angle is the angle between the cleavage. If the estimated angle of nearly 90 degrees, which is more obvious for pyroxene; if a sharp angle or obtuse angle for amphibole. In addition, the ordinary stone often associated with hornblende quartz, feldspar, biotite and clinopyroxene and olivine; often, mafic symbiosis. In granite, hornblende and biotite are sometimes confused, the difference lies in the fact that amphibole hardness is greater than a knife, with a knife carved only clastic particles on the cleavage plane of glass luster; while biotite hardness is less than a knife, with a knife can pick into thin slices, cleavage mask Pearl luster. In addition, amphibole weathering after often with green shades, and biotite weathering often with brown color.

5、辉石

5, the

辉石为超基性岩和基性岩中主要的矿物,另外在安山岩中常以斑晶出现。大多数辉石呈绿黑色,少量辉石呈灰绿色(如透辉石)。产于侵入岩中的辉石一般呈等轴的粒状。辉石具两组近于垂直的解理,常构成不整齐的阶梯状断口。辉石常见的次生变化是蛇纹石化和纤闪石化。蛇纹石交代辉石常形成具丝绢光泽的“绢石”。

Pyroxene is ultrabasic rocks and basic rocks in the main mineral, also in the andesite often appear as phenocrysts. Most of the pyroxene is greenish black and a small amount of pyroxene is greyish green (e.g. Tou Huishi). Pyroxene in intrusive rock is generally equiaxed grain. Pyroxene with two groups of vertical cleavage, often constitute a ladder shaped irregular fracture. The most common secondary changes of pyroxene are the petrochemistry and the petrochemistry. Serpentine metasomatism often formed with pyroxene silk silk stone "".