本文選題：邯邢地區(qū) + 磁鐵礦　； 參考：《中國地質(zhì)大學(xué)》2017年博士論文

【摘要】：邯鄲邢臺(tái)地區(qū)大地構(gòu)造位置屬于華北克拉通之中部造山帶中南段,是我國大型矽卡巖鐵礦床的重要礦集區(qū)。該地區(qū)鐵礦床規(guī)模大,礦石品位高,已發(fā)現(xiàn)的礦床/點(diǎn)100多個(gè),已探明儲(chǔ)量達(dá)8億多噸,是我國重要的富鐵礦礦石產(chǎn)出基地。前人對(duì)該地區(qū)的礦化特征、成礦巖體的侵位時(shí)代和巖石成因等開展了較多研究,但關(guān)于該地區(qū)矽卡巖鐵成礦流體組成、性質(zhì)及演化過程、磁鐵礦沉淀機(jī)制等成礦過程的重要信息和關(guān)鍵問題的研究明顯欠缺,很大程度制約了該地區(qū)成礦規(guī)律和成礦模式總結(jié)。邯鄲邢臺(tái)地區(qū)矽卡巖鐵礦床與中奧陶統(tǒng)的膏巖層空間關(guān)系極為密切,不含膏巖層的早奧陶統(tǒng)灰?guī)r未發(fā)現(xiàn)工業(yè)價(jià)值的磁鐵礦礦化。膏巖層的的加入是否對(duì)形成富鐵礦起到關(guān)鍵作用?論文選取邯邢地區(qū)最為典型的白澗和西石門大型富鐵礦床為研究對(duì)象,在詳細(xì)的野外地質(zhì)觀察基礎(chǔ)上,開展詳細(xì)的礦物學(xué)、地球化學(xué)及流體包裹體研究,深入探討該地區(qū)鐵礦床的成礦流體性質(zhì)及演化、膏巖層作用機(jī)制以及高品位礦體形成機(jī)理,并建立該地區(qū)的矽卡巖鐵礦成礦模式。在符山和白澗侵入體中發(fā)現(xiàn)四類磁鐵礦。第一類為巖漿型磁鐵礦,這類磁鐵礦一般發(fā)育鈦鐵礦出溶結(jié)構(gòu),鈦鐵礦在晚階段熱液作用下蝕變形成榍石。在熱液蝕變過程中,第一類巖漿磁鐵礦常被第二類和第三類的熱液磁鐵礦交代。第四類磁鐵礦為直接從熱液中沉淀的產(chǎn)物,不發(fā)育出溶及孔洞結(jié)構(gòu)。巖漿磁鐵礦在被交代過程中微量元素如Ti、Al、Mg、Mn、Cr、Zn、Ga和Co等含量降低,而Fe含量升高。對(duì)磁鐵礦微量元素用前人所設(shè)計(jì)的微量元素圖解進(jìn)行投點(diǎn)時(shí),發(fā)現(xiàn)這些圖解并不能有效區(qū)分不同成因磁鐵礦(巖漿vs熱液)。通過對(duì)磁鐵礦詳細(xì)的結(jié)構(gòu)觀察和成分分析,我們提出Fe vs V/Ti圖解能有效區(qū)分巖漿磁鐵礦與熱液磁鐵礦,并能檢測(cè)巖漿磁鐵礦的蝕變程度。白澗鐵礦床礦化由早到晚,成礦溫度由高往低可分為三個(gè)階段:(I)干矽卡巖階段;(II)濕矽卡巖階段;(III)硫化物階段。不同階段形成的磁鐵礦微量元素組成存在明顯差異。磁鐵礦中的Ti、V、Cr、Ni、Ga等元素含量從早階段到晚階段依次下降,說明溫度對(duì)這些元素起到重要控制作用。微量元素Co和Ni在黃鐵礦中高度富集,因此與黃鐵礦共生的磁鐵礦往往虧損這兩種元素。Si和Ca等不相容元素在震蕩環(huán)帶結(jié)構(gòu)磁鐵礦中高度富集,反映了了在非平衡條件下,磁鐵礦快速生長,這些元素通過表面吸附作用進(jìn)入磁鐵礦。磁鐵礦溶解再沉淀現(xiàn)象十分多見,這個(gè)過程淋濾了磁鐵礦中雜質(zhì)元素如Si、Ca、Mg和Al等,提高了磁鐵礦純度。對(duì)比白澗層間礦體磁鐵與白澗侵入體中的巖漿磁鐵礦,發(fā)現(xiàn)兩者在結(jié)構(gòu)和微量元素組成上存在巨大差異。層間礦體明顯富集Si和Ca等不相容元素,且發(fā)育震蕩環(huán)帶結(jié)構(gòu),而相容元素Ti、V和Cr等含量比巖漿磁鐵礦低2個(gè)數(shù)量級(jí),顯示了明顯的熱液磁鐵礦特征,并非礦漿貫入成礦。白澗鐵礦礦區(qū)內(nèi)矽卡巖輝石發(fā)育核-幔-邊結(jié)構(gòu),從核部到幔部和邊部,Na和Fe顯著升高,Mg顯著降低。外矽卡巖原生輝石幾乎為純透輝石,部分被晚階段富鐵輝石交代。過渡金屬元素如Ni、Co、V、Cr和Zn等在輝石中的含量主要受輝石Fe含量控制;高場(chǎng)強(qiáng)元素如Nb、Ta、Zr和Hf則與輝石端元成分組成關(guān)系不大,主要受控于溫度和流體成分。稀土元素總量與輝石中的P含量成明顯正相關(guān)關(guān)系,磷灰石沉淀可能是導(dǎo)致輝石中P和REE總量下降的直接的原因。白澗磷灰石強(qiáng)烈富集輕稀土,磷灰石大量沉淀可能導(dǎo)致熱液輕稀土的虧損,具體表現(xiàn)為La/Sm比值降低。綜合輝石結(jié)構(gòu)和成分特征,我們認(rèn)為富鎂的內(nèi)矽卡巖核部輝石和外矽卡巖的原生輝石主要形成于靜巖壓力下的高溫、低鹽度、低水/巖比值的流體擴(kuò)散交代階段(Diffusive matasomastism);富鐵內(nèi)矽卡巖輝石以及外矽卡巖的次生輝石可能主要形成于靜水壓力下,流體發(fā)生沸騰作用,形成高鹽度的富鐵流體,流體受斷裂/角礫巖構(gòu)造控制明顯,具有高的水/巖比值。白澗鐵礦部分礦體發(fā)育在大理巖層間,受斷裂構(gòu)造控制明顯,這套高鹽度富鐵的成礦流體可能是形成白澗高品位層間礦礦石的關(guān)鍵因素。西石門成礦巖體閃長巖中的造巖礦物和干矽卡巖礦物中的流體包裹體含大量不透明子礦物和鹽類子礦物。分析結(jié)果表明,這些包裹體中的不透明子礦物絕大多數(shù)為磁黃鐵礦,透明子礦物為氯化鈉和氯化鉀。透輝石中含透明子晶的包裹體均一溫度為420℃-620℃,集中在500℃左右,鹽度介于42.2-71.8 wt%NaCl,峰值60%wt%NaCl左右;含不透明子晶流體包裹體在加熱過程中并不均一,鹽度51.4-70.8 wt%NaCl,峰值62 wt%NaCl左右。利用體積法估算透輝石包裹體中鐵的含量平均值為4 wt%,最高可達(dá)9 wt%。透輝石中出現(xiàn)大量含黃鐵礦子晶和鹽類子晶的包裹體說明西石門鐵礦的成礦流體為高溫、高鹽度、還原性富鐵流體。邯邢地區(qū)中奧陶統(tǒng)碳酸鹽巖地層中發(fā)育大量蒸發(fā)巖,主要為硬石膏巖和石膏巖,最厚可達(dá)147 m,并形成石膏礦床(礦點(diǎn))30多處;而包括西石門在內(nèi)的邯邢地區(qū)矽卡巖鐵礦床與中奧陶統(tǒng)中的膏巖層關(guān)系十分密切,鐵礦床主要產(chǎn)在中生代巖漿巖與中奧陶統(tǒng)的接觸帶,其次為離接觸帶不遠(yuǎn)的碳酸鹽層間構(gòu)造帶;相反,侵位于石炭系和二疊系地層(不含膏巖層)中的巖體未發(fā)現(xiàn)有工業(yè)價(jià)值鐵礦,只伴有黃鐵礦化或硫鐵礦礦床。由于膏鹽層中的SO42-在高溫條件下具很強(qiáng)的氧化性,在矽卡巖鐵礦成礦過程中可以起到很好的氧化劑作用。邯邢地區(qū)鐵礦石中硫化物的δ34S‰為6.0-18.7‰,多集中在11.6-18.7‰之間,具有海相硫酸鹽的硫同位素組成特征;而礦區(qū)侵入巖中δ34S‰主要集中在2.5-6.5之間,為深源巖漿硫的特點(diǎn)。這說明邯邢地區(qū)矽卡巖鐵礦熱液成礦過程中有大量奧陶系膏鹽層的加入。還原性質(zhì)的巖漿流體與高氧逸度的溶解膏巖層的外部流體混合將導(dǎo)致成礦流體氧逸度升高和磁鐵礦的沉淀:12Fe~(2+)+SO_4~(2-)+12H_2O = 4Fe_3O_4 + H_2S+22H~+雖然上述反應(yīng)產(chǎn)生大量的H~+,H~+可通過與圍巖碳酸巖反應(yīng)被消耗,從而促進(jìn)反映持續(xù)向右進(jìn)行、磁鐵礦不斷沉淀,形成較大規(guī)模的高品位磁鐵礦礦體。上述反應(yīng)對(duì)熱液鐵礦成礦過程中二價(jià)鐵氧化成三價(jià)鐵的機(jī)制提供了新的見解和證據(jù),同時(shí)也很好地解釋了許多與熱液磁鐵礦相關(guān)的礦床如矽卡巖型鐵礦床、鐵氧化物銅(金)礦床以及磁鐵礦-磷灰石礦床中出現(xiàn)大量富集重硫的硫化物的原因。以上研究表明,邯邢地區(qū)矽卡巖富鐵礦早階段成礦流體在上升過程中可能發(fā)生沸騰作用,形成的流體具有高溫、高鹽度、氧逸度低的特點(diǎn),這樣的流體能溶解大量的Fe。高鹽度流體與正在冷卻的巖漿巖充分反應(yīng),導(dǎo)致區(qū)域大范圍的強(qiáng)烈的鈉鈣質(zhì)蝕變,在此過程中成礦流體萃取大量的鐵質(zhì),為形成大型富鐵礦床提供了成礦物質(zhì)基礎(chǔ)。沸騰包裹體測(cè)溫?cái)?shù)據(jù)計(jì)算表明邯邢地區(qū)成礦深度較淺(5km),巖漿流體向上遷移過程中容易快速冷卻,這個(gè)過程不利于形成富鐵的石榴子石和輝石等礦物,因而熱液中的鐵質(zhì)沒有被大量消耗。成礦流體在上升過程中與圍巖中的膏巖層反應(yīng)或者與溶解膏巖層的外部流體混合,導(dǎo)致成礦流體氧逸度突然升高,從而大量的Fe2+被氧化形成Fe3+,磁鐵礦在這個(gè)過程中大量沉淀。另一方面膏巖層物質(zhì)的溶解形成的大理巖中的構(gòu)造薄弱帶是重要的控礦構(gòu)造,由于離巖體較遠(yuǎn)且處于相對(duì)開放的空間,成礦流體能有效聚集并快速冷卻,在此過程中成礦流體與圍巖反應(yīng),磁鐵礦快速的大量的沉淀,形成致密塊狀的高品位磁鐵礦體。晚階段流體能與早階段形成的富含雜質(zhì)元素的磁鐵礦反應(yīng),磁鐵礦發(fā)生溶解再沉淀,雜質(zhì)顯著降低,磁鐵礦純度得到提高,從而對(duì)鐵礦石得到進(jìn)一步的富集。
[Abstract]:The geotectonic position of the Xingtai area in Handan is in the middle and south section of the Central Orogenic Belt of the North China Craton. It is an important ore collection area of the large skarn iron deposit in China. This area has large scale, high ore grade, more than 100 found ore deposits / points and more than 800 million tons of proven reserves. It is an important ore producing base in China. The mineralizing characteristics of the area, the emplacement age of the ore-forming rock mass and the petrogenesis have been studied more, but the important information and key problems about the composition, nature and evolution process of the skarn iron ore-forming fluid, the deposit mechanism of magnetite and so on are obviously deficient, and the metallogenic regularity and formation of this area have been restricted to a great extent. The ore pattern is summed up. The skarn deposit in Xingtai area of Handan is closely related to the gypsum rock in the Middle Ordovician, and the early Ordovician limestone without gypsum rock has not found the magnetite mineralization of industrial value. Is the gypsum rock formation playing a key role in the formation of rich iron ore? The paper selects the most typical Bai Jian and Xi Shi in Hanxing area. On the basis of detailed field geological observation, the detailed mineralogy, geochemical and fluid inclusions are carried out on the basis of detailed field geological observation. The characteristics and evolution of the ore-forming fluid in the iron deposit in this area, the mechanism of the gypsum rock stratum and the mechanism of the high grade ore form, and the formation of the skarn ore-forming in this area are established. Four types of magnetite are found in the rune and Bai Jian intrusions. The first class is magmatic magnetite. This kind of magnetite usually develops ilmenite dissolving structure, and ilmenite is altered to form titanite in the late stage of hydrothermal solution. In the process of hydrothermal alteration, the first class magmagnetite is often replaced by second types of magnetite and third types of hydrothermal magnetite. The four type magnetite is a product that precipitates directly from the hydrothermal solution and does not develop dissolution and pore structure. In the process of metasomatism, the trace elements such as Ti, Al, Mg, Mn, Cr, Zn, Ga and Co are reduced and the content of Fe is increased. Different genetic magnetite (magma vs hydrothermal fluids) are distinguished effectively. Through detailed structural observation and composition analysis of magnetite, we suggest that Fe vs V/Ti diagrams can effectively distinguish magmagnetite from hydrothermal magnetite and detect the alteration degree of magmagmagnetite. The mineralization temperature of the Bai Jian iron deposit from high to late can be divided into three from high to low. Phase: (I) dry skarn stage; (II) wet skarn phase; (III) sulfide phase. The composition of trace elements of magnetite in different stages is distinct. The content of Ti, V, Cr, Ni, Ga in magnetite decreased from the early stage to the late stage, indicating that temperature plays an important control role in these elements. Trace elements Co and Ni are in yellow. The iron ore is highly enriched, so the magnetite, which is symbiotic with pyrite, often loses the loss of the two elements,.Si and Ca, which are highly enriched in the concussion belt structure magnetite, reflecting the rapid growth of magnetite under unbalanced conditions. These elements are absorbed into magnetite by surface adsorption. Magnetite dissolves and re precipitates ten. The impurity elements in magnetite, such as Si, Ca, Mg and Al, have been leached to improve the purity of magnetite. The comparison of the magmagmagnetite in the white Jian interlayer magnets and the Bai Jian intrusive body shows that there are great differences in the structure and the composition of the trace elements. The interlayer ore bodies obviously enrich the incompatible elements such as Si and Ca, and develop concussion. The content of Ti, V and Cr of the compatible elements is 2 orders of magnitude lower than that of magmagnetite. It shows obvious characteristics of the hydrothermal magnetite, not the ore slurry penetrated into the mineralization. The skarn pyroxene development nuclear mantle edge structure in the Bai Jian iron mine area, from the nucleus to the mantle and the edge, Na and Fe significantly increased, and the Mg was significantly reduced. The outer silicon card Iwahara Yukiishi was almost the same. The content of transition metal elements such as Ni, Co, V, Cr and Zn in pyroxene is mainly controlled by the Fe content of pyroxene, and the high field elements such as Nb, Ta, Zr and Hf are not closely related to the composition of the pyroxene end element, mainly controlled by the temperature and fluid components. The total amount of rare earth elements and the P content of pyroxene. Obviously positive correlation, apatite precipitation may be the direct cause of the decrease in the total amount of P and REE in the pyroxene. The white ravine apatite is strongly enriched with light rare earth, and a large amount of apatite precipitates may lead to the loss of the light rare earth of the hydrothermal solution. The specific expression is the reduction of the La/Sm ratio. The primary pyroxene of the pyroxene and outer skarn is mainly formed at high temperature, low salinity, and low water / rock ratio of the fluid diffusion metasomatism (Diffusive matasomastism), and the secondary pyroxene in the iron rich skarn pyroxene and the outer skarn may be mainly formed under the hydrostatic pressure, the fluid is boiling, and the high salinity is formed. The fluid is controlled obviously by the fracture / breccia structure and has a high water / rock ratio. The part of the Bai Jian iron ore body is developed between the marble layers and is controlled obviously by the fracture structure. The high salinity and iron rich metallogenic fluid may be the key factor for the formation of high grade interlayer ore in the Bai Jian. The rock ore in the diorite of the West Shimen ore-forming rock mass The fluid inclusions in the mineral and dry skarn minerals contain a large number of opaque subminerals and salt subminerals. The analysis results show that most of the opaque subminerals in these inclusions are pyrrhotite, hyaluronic minerals are sodium chloride and potassium chloride. The homogeneous temperature of the transparent subcrystal in Diopside is 420 C -620 C, concentrated in 500. The salinity is around 42.2-71.8 wt%NaCl and the peak value is about 60%wt%NaCl, and the fluid inclusions containing opaque subcrystal are not homogeneous during the heating process, and the salinity 51.4-70.8 wt%NaCl is about 62 wt%NaCl. The average value of the iron content in the diopside inclusions is estimated to be 4 wt% by using the volume method, and the maximum of the 9 wt%. diopside can be found to contain a large number of yellow iron. The inclusions of ore subcrystal and salt subcrystal indicate that the ore-forming fluid of West Shimen iron ore is high temperature, high salinity and reductive iron rich fluid. The Middle Ordovician carbonate strata in the Middle Ordovician of Hanxing area are mainly composed of anhydrite and gypsum rock, with the thickness of up to 147 m and more than 30 places in the stone gypsum deposit (ore point), including West Shimen. The skarn iron deposit in Hanxing area is closely related to the ointment strata in the Middle Ordovician. The iron ore deposit is mainly produced in the contact zone of Mesozoic Magmatic Rock and Middle Ordovician, followed by the carbonate interlayer structural belt, which is not far from the contact zone. On the contrary, the rock mass in the Carboniferous and Permian strata (without the gypsum rock) has not been found to have industrial value. Iron ore is only accompanied by pyrite or pyrite ore. Because the SO42- in the gypsum salt layer has strong oxidation under high temperature, it can play a very good oxidizing agent in the metallogenic process of skarn iron ore. The sulphide in the iron ore of Hanxing area is 6.0-18.7% 34S per 1000, in the multiple collection of 11.6-18.7 per thousand, with marine sulphate. The characteristics of sulfur isotopes are characterized, and the delta 34S per 1000 in the mining area is mainly concentrated in the 2.5-6.5, which is the characteristic of the deep source magma sulfur. This indicates that a large number of Ordovician gypsum salts are added to the hydrothermal mineralization process of the skarn iron mine in Hanxing area. The increase of oxygen fugacity of ore fluid and the precipitation of magnetite: 12Fe~ (2+) +SO_4~ (2-) +12H_2O = 4Fe_3O_4 + H_2S+22H~+, although the above reaction produces a large amount of H~+, H~+ can be consumed by the reaction with the rock carbonatite, thus promoting the continuous reflection to the right, magnetite precipitation and the formation of a large scale high grade magnetite ore. The mechanism of the oxidation of two valent iron into trivalent iron during the metallogenic process of hydrothermal iron ore provides new insights and evidence. At the same time, it is well explained that many of the ore deposits associated with hydrothermal magnetite, such as skarn type iron deposits, iron oxide copper (gold) deposits and magnetite apatite deposits, are caused by a large amount of sulphur enriched in the magnetite ore deposit. The study shows that the early stage of ore-forming fluid in the skarn iron ore rich iron ore in Hanxing area may be boiling in the process of rising, and the fluid is characterized by high temperature, high salinity and low oxygen fugacity. This fluid can dissolve a large number of Fe. high salinity fluids and fully react with the cooling magma rock, resulting in a large area of strong sodium calcium. In this process, the ore-forming fluid extracts a large amount of iron, which provides a material basis for forming large iron rich deposits. The calculation of the temperature measurement data of the boiling inclusions indicates that the metallogenic depth of the Hanxing area is shallow (5km), and the magma fluid is easy to cool rapidly during the upward migration process. This process is not conducive to the formation of iron rich pomegranite and pyroxene. The iron in the hydrothermal solution is not consumed much. The ore-forming fluid reacts with the gypsum rock layer in the surrounding rock or mixed with the external fluid of the dissolved gypsum rock, resulting in a sudden increase in oxygen fugacity of the ore-forming fluid, so that a large number of Fe2+ are oxidized to Fe3+, and the magnetite is precipitated in a large amount in this process. On the other hand, the gypsum rock is on the other hand. The structural weak zone in marble formed by the dissolution of the layer material is an important ore controlling structure. The ore-forming fluid can be effectively aggregated and cooled rapidly because of the distant and relatively open space from the rock mass. In this process, the ore-forming fluid is reacting with the surrounding rock, and the magnetite is rapidly precipitated, forming a dense and massive high grade magnet ore body. The late phase fluid can react with the magnetite rich in the early stage, which is rich in impurity elements. The magnetite is dissolved and reprecipitated, the impurity is reduced significantly, the purity of magnetite is improved and the iron ore is enriched further.
【學(xué)位授予單位】：中國地質(zhì)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2017
【分類號(hào)】：P618.31
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本文編號(hào)：2077620