Presentation on theme: "Chapter 2 Rock 第二章 岩石. 1 造岩矿物的概念 Since minerals are the building blocks of rocks, it is important that you learn to identify the most common varieties."— Presentation transcript:
Chapter 2 Rock 第二章 岩石
1 造岩矿物的概念 Since minerals are the building blocks of rocks, it is important that you learn to identify the most common varieties. Minerals can be distinguished using various physical and/or chemical characteristics, but, since chemistry cannot be determined readily in the field, the physical properties of minerals are used to identify them. §2-1: The main minerals in the rock( 造岩矿物 )
Physical properties of minerals include ： ♥ Crystal form （晶形） ♥ Hardness （硬度） (relative to a steel blade or you finger nail), ♥ colour( 真色，假色，它色 ) ♥ Luster （光泽） ♥ Streak ( 条痕 ) (the colour when a mineral is ground to a powder). ♥ cleavage （解理） 2 矿物的物理性质
Quartz is hard - it can easily scratch a steel knife blade. In many rocks, quartz grains are irregular in shape because crystal faces are rare and quartz does not have a cleavage(ie, it does not break on regular flat faces). （ 1 ） Quartz( 石英 ): Quartz is a glassy looking, transparent or translucent mineral which varies in colour from white and grey to smoky. When there are individual crystals they are generally clear, while in larger masses quartz looks more milky white. 油脂光泽 2 常见矿物介绍
Feldspar is also hard but can be scratched by quartz. Feldspar in igneous rocks （火成岩） forms well developed crystals which are roughly rectangular in shape, and they cleave or break along flat faces. The grains, in contrast to quartz, often have straight edges and flat rectangular faces, some of which meet at right angles. （ 2 ） Feldspar （长石） : Feldspar is the other common, light-coloured rock-forming mineral. Instead of being glassy like quartz, it is generally dull to opaque （不透明） with a porcelain-like appearance. Colour varies from red, pink (orthoclase 正长石 ), and white to green, grey (plagioclase 斜长石 ).
Plagioclase 斜长石 Orthoclase 正长石
The most common amphibole is hornblende （角闪石）. Hornblende is quite similar to augite （普通辉石） in that both are dark minerals, however hornblende crystals are generally longer, thinner and shinier than augite and the mineral cross- sections are diamond-shaped. hornblende （角闪石） （ 3 ） Amphibole （闪石）
The most common pyroxene mineral is augite. Augite is generally dark green to black in colour and forms short, stubby （短而粗） crystals which, if you look at an end-on section, have square or rectangular cross-sections. Pyroxene （辉石） （ 4 ） Pyroxene 辉石
Talc occurs in granular （粒状的） or foliated （片状的） masses sometimes known as soapstone （皂石）. It is white to green, sometimes grey or brownish. It is very soft and will be scratched by a finger nail. It has a greasy feel （滑 感） （ 5 ） Talc （滑石）
Olivine in the jewellery trade, is yellow-green, translucent （半透明 的） and glassy looking. Crystals are not common; it usually occurs as rounded grains in igneous （火 成的） rocks or as granular masses. Olivine is almost as hard as quartz; it does not have a well- developed cleavage. （ 6 ） Olivine 橄榄石
Mica is easily distinguished by its characteristic of peeling into many thin flat smooth sheets or flakes （薄片）. This is similar to the cleavage in feldspar except that in the case of mica the cleavage planes are in only one direction and no right angle face joins occur. Mica may be white and pearly or dark and shiny. （ 7 ） Mica 云母
§2-2: Rock( 岩石 ) igneous rock （岩浆岩） (magma rock) sedimentary rock （沉积岩） metamophic rock （变质岩） 岩石 一 、 The classification of rock according to the cause of formation 岩石的基本概念：一种或多种矿物组成的集合体 )
二、 Igneous rock 1 the formation of igneous rock: Deep within the Earth, rock is kept in a molten （融熔的） state due to extreme temperature and pressure. This molten rock is called magma （岩浆）. The magma is constantly moving and sometimes moves its way to the surface through the cracks （裂缝） in the solid rock. Once it reaches the surface, it is called lava （熔 岩）.
The location it pushes through to the surface is called a volcano （火山）. The opening in the volcano that the lava erupts out of is called a vent( 出口 ). For many volcanos, there is more than one vent. Often volcanos have a funnel （漏斗） shape with a pit at the top. This pit is called a volcanic crater （火山口）. If this crater becomes very large, the walls of the crater might collapse to produce a feature called a caldera （喷火山口）
How Igneous rock rock Is Formed
2 the formation state of igneous rock （岩浆岩的产状） Batholith 岩基 Captive mass 俘虏体 laccolith 岩盘 岩墙 Rock wall 岩株 Volcano neck 火山颈 Lava flow 岩流 Sill 岩床
3 the classcification of igneous rock （岩浆岩的分类） （ 1 ） According to the formation state( 按产状 ) ◈ Intrusive Igneous Rocks （侵入岩） - usually medium to coarse grained texture due to slow cooling. Typically light coloured. ◈ Extrusive Igneous Rocks （喷出岩） - glassy or fine-grained due to rapid cooling. May have voids due to degassing of the magma. Typically dark coloured.
(2) According to the Silica Content and Mineral Composition( 根据二氧化硅含量 ) ◈ Acid Igneous Rocks( 酸性岩 ) - silica rich ( > 65% by weight) composed mainly of light coloured minerals (eg. feldspars, quartz) ◈ Intermediate Igneous Rocks （中性岩） -silica 50-65% by weight, composed mainly of feldspars, some mafic （铁镁质的 minerals, with some quartz.
◈ Basic Igneous Rocks （基性岩） - silica poor ( < 50% by weight) contain significant amounts of mafic or dark coloured ferromagnesian minerals (eg. olivines, pyroxenes, amphiboles, micas). No free quartz.
◈ granite （花岗岩） Granite is an igneous rock that is composed of four minerals. These minerals are quartz, feldspar, mica, and usually hornblende. Granite forms as magma cools far under the earth's surface. Because it hardens deep underground ， it cools very slowly. This allows crystals of the four minerals to grow large enough to be easily seen by the naked eye. 4 the description of main igneous rock （岩浆岩描述）
Granite is an excellent material for building bridges and buildings because it can withstand thousands of pounds of pressure. It is also used for monuments because it weathers slowly. Engravings in the granite can be read for hundreds of years, making the rock more valuable. Granite is quarried in many places in the world including the United States. The State of New Hampshire has the nickname "Granite State" because of the amount of granite in the mountains of that beautiful state. The Canadian Shield of North America contains huge outcroppings (surface rocks) of granite.
◈ rhyolite （流纹岩） Rhyolite is very closely related to granite. The difference is rhyolite has much finer crystals. These crystals are so small that they can not be seen by the naked eye. Rhyolite is an extrusive igneous rock having cooled much more rapidly than granite, giving it a glassy appearance. The minerals that make up rhyolite are quartz, feldspar, mica, and hornblende.
1 abyssal intrusive rock 2 well crystallization 3 feldspar, quartz, amphibole ◈ Diorite ( 闪长岩 ) ◈ Diorite porphyrite （闪长玢岩） 1 shallow intrusive rock, 2 median crystallization 3 feldspar, quartz amphibole
Dacite is an extrusive igneous rock. The principle minerals that make up dacite are plagioclase, quartz, pyroxene, or hornblende. Dacite 安山岩 ◈ Dacite （安山岩） Dacite 安山岩
1 abyssal intrusive rock 2 well crystallization 3 amphibole, phyroxene feldspar ◈ pyroxenire ( 辉岩 ) 1 ultrabasic rock （超基性岩石） (sio 2 <45%) 2 abyssal intrusive rock （深成岩） 3 well crystallization （结晶好） 4 olivine ； pgroxene ◈ olivine rock( 橄榄岩 )
Basalts are dark colored, fine- grained extrusive rock. The mineral grains are so fine that they are impossible to distinguish with the naked eye or even a magnifying glass （放大镜）. They are the most widespread of all the igneous rocks. Most basalts are volcanic in origin and were formed by the rapid cooling and hardening of the lava flows. Some basalts are intrusive having cooled inside the Earth's interior. ◈ basalt 玄武岩
◈ Obsidian 黑耀岩 Obsidian is a very shiny natural volcanic glass. When obsidian breaks it fractures with a distinct conchoidal （贝壳状的） fracture. Notice in the photo to the left how it fractures. Obsidian is produced when lava cools very quickly. The lava cools so quickly that no crystals can form.
When people make glass they melt silica rocks like sand and quartz then cool it rapidly by placing it in water. Obsidian is produced in nature in a similar way. Obsidian is usually black or a very dark green, but it can also be found in an almost clear form.
Pumice is a very light colored, frothy （起泡的） volcanic rock. Pumice is formed from lava that is full of gas. The lava is ejected and shot through the air during an eruption. As the lava hurtles （急飞） through the air it cools and the gases escape leaving the rock full of holes. ◈ Pumice （浮石）
Pumice is so light that it actually floats on water. Huge pumice blocks have been seen floating on the ocean after large eruptions. Some lava blocks are large enough to carry small animals.
三、 sedimentary rock （沉积岩） 1 the formation of sedimentary rock: For thousands, even millions of years, little pieces of our earth have been eroded--broken down and worn away by wind and water. These little bits of our earth are washed downstream where they settle to the bottom of the rivers, lakes, and oceans. Layer after layer of eroded earth is deposited on top of each. These layers are pressed down more and more through time, until the bottom layers slowly turn into rock.
How Sedimentary Rock Is Formed
Sediments are subdivided into three types: （ 1 ） Clastic or detrital sediments （碎屑岩） Comprising particles of various sizes carried in suspension by wind, water or ice. Sand ( 砂岩 )is an example of a clastic sediment. Silt （粉砂岩） and sand size particles are carried in suspension by wind, water and ice. 2 the classification of sedimentary rock:
（ 2 ） Chemical or precipitated sediments （化学岩） which are carried in aqueous solution. Salt (halite) is an example of a chemical precipitate. · （ 3 ） Organic or biogenic sediments （有机岩） precipitated or accumulated by biological agents. Many organisms promote the precipitation of calcite to form biogenically precipitated calcareous （含钙的） muds.
3 The texture and structure of sedimentary rock 沉积岩的结构和构造 平行层理 斜层理 波状层理 印模 粒序层理 交叉层理 沉积岩的层理构造
沉积岩的结构特征 砂粒 孔隙 胶结物 砂粒 粘粒 粉粒
Sphericity 球形度 [ sfe’risiti ]
4 the description of sedimentary rock Conglomerate rocks are sedimentary rocks. They are made up of large sediments like sand and pebbles （鹅卵 石）. The sediment is so large that pressure alone cannot hold the rock together; it is also cemented together with dissolved minerals. ◈ gravel stone (conglomerate) 砾岩 (clastic rock)
◈ sand stone (d=2-0.05mm) 砂岩 Sandstone rocks are sedimentary rocks made from small grains of the minerals quartz and feldspar. They often form in layers as seen in this picture. They are often used as building stones.
◈ silt stone(d= mm) 粉砂岩 ◈ mud stone (d<0.005mm) 泥岩 kaolinite( 高岭石 ) montorillonite （蒙脱石） water mica （伊利石） Mineral Composition
Shale rock is a type of sedimentary rock formed from clay that is compacted together by pressure. They are used to make bricks ◈ shale stone(d<0.005mm) 页岩
Limestone rocks are sedimentary rocks that are made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells. This rock is used in concrete and is an excellent building stone for humid regions. color grey ◈ lime stone 石灰岩
◈ dolomite rock 白云岩 color: white-grey mineral: dolomit ◈ Gypsum 石膏 Gypsum rocks are sedimentary rocks made up of sulfate mineral and formed as the result of evaporating sea water in massive prehistoric basins. It is very soft and is used to make Plaster of Paris, casts, molds, and wallboards.
四、 Metamorphic rock （变质岩） Metamorphic rocks are generated by recrystallization of either igneous or sedimentary rocks by the action of any or all of the following: Pressure, Temperature, Pore Fluids.
The type of metamorphic rock is determined by the parent rock （母岩） and the P/T conditions. In general, metamorphism causes: Growth of new minerals Deformation and rotation of mineral grains Recrystallization of minerals as larger grains 1 the formation and classification of Metamorphic rocks
2 the description of Metamorphic rocks ◈ Marble （大理岩） Marble is metamorphosed limestone or dolomite. Both limestone and dolomite have a large concentration of calcium carbonate (CaCO3). Marble has many different sizes of crystals.
Marble has many color variances due to the impurities( 杂质 ) present at formation. Some of the different colors of marble are white, red, black, mottled and banded, gray, pink, and green. Marble is much harder than its parent rock. This allows it to take a polish which makes it a good material for use as a building material, making sink tops, bathtubs, and a carving stone for artists. Today, headstones are made from marble and granite because both of these rocks weather very slowly and carve well with sharp edges.
◈ Quartzite （石英岩） Quartzite is composed of sandstone that has been metamorphosed. Quartzite is much harder than the parent rock, sandstone. It forms from sandstone that has come into contact with deeply buried magmas. Quartzite looks similar to its parent rock. The best way to tell quartzite from sandstone is to break the rocks. Sandstone will shatter into many individual grains of sand while quartzite will break across the grains.