本文選題：若爾蓋鈾礦田　切入點：硅質(zhì)巖　出處：《成都理工大學》2015年碩士論文　論文類型：學位論文

【摘要】：若爾蓋鈾礦田主要位于四川省若爾蓋縣境內(nèi)南秦嶺鈾成礦帶西段,其主體部分為由古生界地層構(gòu)成的白龍江復(fù)背斜,是中國重要的碳硅泥巖型鈾礦產(chǎn)地。礦床群主要產(chǎn)于下志留統(tǒng)羊腸溝組、塔爾組和拉垅組一套淺變質(zhì)硅-灰?guī)r系中,并嚴格受巖性、構(gòu)造和地球化學環(huán)境控制,是目前中國礦床數(shù)量最多、規(guī)模最大、工業(yè)意義和經(jīng)濟意義顯著且發(fā)展前景明朗的碳硅泥巖型鈾礦田,因而倍受廣大礦床地質(zhì)工作者所關(guān)注。硅質(zhì)巖是若爾蓋鈾礦田碳硅泥巖型鈾礦的重要含礦巖石之一。區(qū)內(nèi)硅質(zhì)巖依據(jù)結(jié)構(gòu)和成因可分為泥晶硅質(zhì)巖、變晶硅質(zhì)巖、硅化硅質(zhì)巖以及鈣化硅質(zhì)巖四種類型。本文主要從硅質(zhì)巖的常量元素地球化學、微量元素地球化學、稀土元素地球化學以及硅同位素地球化學等特征來查明若爾蓋鈾礦田含礦巖系中硅質(zhì)巖的成因。以因子分析方法為基礎(chǔ),系統(tǒng)分析各含礦主巖、熱液礦物(石英、方解石)、礦石微量元素之間的相關(guān)性,探討硅質(zhì)巖與鈾成礦的關(guān)系等。通過本文的研究,取得了以下成果認識:1.硅質(zhì)巖常量元素地球化學特征硅質(zhì)巖中的SiO2含量平均值為95.72%,表明巖石中幾乎不含陸源泥質(zhì)沉積物。其Al/(Al+Fe+Mn)比值均值為0.21,Fe/Ti比值均值為55.69,(Fe+Mn)/Ti比值均值為61.78,這些比值特征均表明其為熱水沉積成因。在Al-Fe-Mn三角圖和Al2O3-SiO2成因標準模式圖上,硅質(zhì)巖的投點亦均投影在熱水成因區(qū)內(nèi)。MnO/TiO2平均值為5.226,反映硅質(zhì)巖可能形成于深海盆地環(huán)境;MgO/Al2O3平均值高達0.940,表明其形成于高鹽度的海水沉積環(huán)境。2.硅質(zhì)巖微量元素地球化學特征本區(qū)硅質(zhì)巖中的微量元素具高U元素含量而低Zr元素含量特征,暗示其可能為熱水成因且形成環(huán)境可能遠離陸源沉積。Th/U比值、Sr/Ba比值均遠小于1,表現(xiàn)出明顯的熱水成因,同時Rb/Sr比值偏低,反映了硅質(zhì)巖沉積時有富鐵鎂質(zhì)物源加入,說明當時存在強烈的擴張裂解作用。3.硅質(zhì)巖稀土元素地球化學特征區(qū)內(nèi)硅質(zhì)巖的稀土元素北美頁巖標準化配分曲線呈左傾型,多數(shù)樣品中具有負Ce異常和弱的正Eu異常,其δCe平均值為0.80,δEu平均值為1.2,具有熱水沉積硅質(zhì)巖的典型特征。4.硅質(zhì)巖同位素地球化學本區(qū)灰黑色紋層狀硅巖的?30Si值為-0.4‰~+0.2‰(平均值為0.017‰),顯示為遠離大陸的深海沉積。石英脈的?30Si值為-0.1‰~+0.5‰(平均值為0.25‰),為熱水來源的石英。硅灰過渡巖石的?30Si值為-0.2‰,表明硅化的過程有地下熱水參與。礦化硅巖的?30Si值為-0.1‰~+0.5‰,說明在原始深水有熱水參與的化學沉積硅巖基礎(chǔ)上,受到了成礦期含礦熱液的再次改造。5.含礦巖類與鈾成礦關(guān)系若爾蓋鈾礦田含礦巖系中各種巖石的微量元素特征表明,硅質(zhì)巖、礦化硅質(zhì)巖、硅灰?guī)r、硅質(zhì)巖礦石等富集的微量元素種類具有一定的相似性,在微量元素原始地幔標準化蛛網(wǎng)圖上可明顯分為兩類不同的配分曲線,其中英安斑巖與板巖具有相似的配分形態(tài),而硅質(zhì)巖、礦化硅質(zhì)巖、硅灰?guī)r、硅質(zhì)巖礦石、礦化硅灰?guī)r、灰?guī)r、熱液方解石脈及石英脈等的配分曲線大體一致,反映鈾成礦與硅質(zhì)巖、硅-灰?guī)r以及熱液方解石脈和石英脈等關(guān)系密切。本區(qū)含礦巖類具有代表意義的主因子有六個。分別為F1主因子:Cr-GaZr-Nb-Hf-Ta-W-Pb-Th,代表深源的英安斑巖和板巖;F2主因子:LiBe-Sc-Ga-Rb-Zr-Nb-Cs-Hf-Th,代表陸源細碎屑巖類的微量元素組合;F3主因子:Co-Ni-Zn-Y-Mo-U,代表成礦期的方解石脈礦石及部分硅灰?guī)r;F4主因子:V-Cu-Mo-U,代表硅巖礦石及部分含礦方解石脈;F5主因子:Bi-Pb-Ba,代表沉積硅巖;F6主因子:Sr,代表沉積灰?guī)r及硅化灰?guī)r。其中,F5主因子與F6主因子關(guān)系密切,為海洋化學沉積成因;F2主因子、F3主因子、F4主因子關(guān)系較為密切,與礦化作用過程有關(guān);F1主因子相對對立。由此表明成礦與硅巖、硅-灰?guī)r以及熱液方解石脈和石英脈等關(guān)系密切。6.硅質(zhì)巖的成礦意義本區(qū)硅質(zhì)巖鈾平均含量達10.955×10-6,而釷平均含量僅有0.534×10-6,Th/U只有0.059,屬富鈾的沉積建造。該地區(qū)硅質(zhì)巖極低的Th/U值可能暗示巖石中的U主要為活性鈾。因此,若爾蓋含礦巖系中硅質(zhì)巖的高鈾含量和極低的Th/U值對鈾的成礦十分有利,由熱水沉積作用所形成的硅質(zhì)巖系為后期鈾的成礦奠定了良好的物質(zhì)基礎(chǔ)。本區(qū)鈣化硅巖(硅灰?guī)r)不僅孔隙度大,而且易于產(chǎn)生脆性變形而形成層間破碎帶,利于含礦熱液在其中進行運移和沉淀富集。因此硅質(zhì)巖不僅是成礦的有利礦源層,由硅質(zhì)巖經(jīng)碳酸鹽化所形成的鈣化硅巖(硅灰?guī)r)亦為成礦提供了十分有利的空間。上述認識對于深化若爾蓋鈾礦田的礦床成因認識,指導該地區(qū)的鈾礦找礦勘查工作具有重要的指導意義。
[Abstract]:Joel Guy is located in the western part of the territory of Sichuan Province, the main ore field in Ruoergai County in southern Qinling Mountains uranium metallogenic belt, the main part of the grounds of Paleozoic strata composed of white Longjiang anticlinorium, is an important Chinese carbon silicon mudstone type uranium deposit deposit group is mainly produced in the producing area. The Lower Silurian narrow ditch group, Tal Group and pull long epimetamorphic silicon group grey rocks, and strictly controlled by the lithology, tectonic and geochemical environment, is currently the largest number of the largest Chinese deposit, industry, and economic significance is obvious and the development prospects of carbon silicon mudstone type uranium ore field, the ore geologists and thus much attention. The siliceous rocks is one of the important ore bearing rock Joel Guy carbon silicon mudstone type uranium ore field in the region. Based on the structure and origin of siliceous rocks can be divided into argillaceous siliceous rocks, metacryst siliceous rocks, siliceous rocks and siliceous rocks of silicified calcification in four types. This paper mainly from silicon Major elements of rock geochemistry, trace element geochemistry, REE geochemistry and isotopic geochemical characteristics of silicon to genesis of siliceous rocks in Ruoergai uranium ore field, the ore bearing rock series in. Using factor analysis method based on system analysis of the ore hosting rocks, hydrothermal minerals (quartz, calcite), the correlation between to explore the relationship between trace elements of ores, rocks and siliceous uranium mineralization. Through this research, the following results have been achieved: the content of SiO2 1. siliceous rock major element geochemistry of siliceous rocks in the average value of 95.72%, indicating that the rock contains few terrigenous mud sediments. The mean ratio of Al/ (Al+Fe+Mn) 0.21, the ratio of Fe/Ti mean value is 55.69, the ratio of /Ti (Fe+Mn) value was 61.78, the ratio of these features indicate that the hydrothermal sedimentary origin. In the Al-Fe-Mn diagram and Al2O3-SiO2 of standard patterns, siliceous rocks Cast point are also projected in the hydrothermal area.MnO/TiO2 with an average of 5.226, reflecting the siliceous rocks formed in deep sea basin environment; the average MgO/Al2O3 value of up to 0.940, suggesting that the trace elements formed in high salinity seawater sedimentary environment.2. siliceous rock trace element geochemical characteristics of the siliceous rocks in the area with high U content while the low content of Zr element, suggesting that it may be hot water causes and the formation of terrigenous sedimentary environment may be away from the.Th/U ratio, Sr/Ba ratio is far less than 1, showing obvious causes of hot water, while the Rb/Sr ratio is low, reflecting the sedimentary siliceous rocks have rich mafic source added that rare earth elements, there was a strong expansion cracking.3. siliceous rock geochemical characteristics of rare earth elements in the area of the siliceous rocks of North American shale normalized REE curve is left leaning, with negative Ce anomaly and weak positive Eu anomalies in most samples, the The average value of Ce is 0.80 Eu, an average of 1.2, with the typical characteristics of chert siliceous rock.4. isotopic geochemistry of the black lamellar siliceous rocks? 30Si = -0.4% ~+0.2% (average 0.017 per thousand), shown as deep-sea sediments far from the mainland. Quartz veins? The 30Si value is -0.1% ~+0.5% (average 0.25 per thousand), for the hot water source of quartz. Wollastonite transition rock? 30Si value is -0.2%, that the process of the underground water in the silicified rocks. Mineralization of silicon? 30Si value is -0.1% ~+0.5%, the hot water and the chemical sedimentary siliceous rocks based on the original deep water, by the mineralization of ore fluid containing.5. re transformation of various rock ore rock type relationship with uranium mineralization in Ruoergai uranium ore field, the ore bearing rock series in the trace element characteristics indicate that the mineralization of siliceous rocks, siliceous rocks, limestone, kinds of trace element enrichment of siliceous rock ore etc. There are some similarities, in the spider diagram of trace elements in primitive mantle standard can be obviously divided into two different types of distribution curve, which is similar to the dacite porphyry and slate with morphology, and siliceous rocks, mineralization of chert, siliceous limestone, siliceous rock and ore mineralization, limestone, limestone, hydrothermal calcite and quartz vein and the distribution curve is consistent, reflecting the uranium mineralization and siliceous rocks, silicon limestone and hydrothermal calcite and quartz veins are closely related. The main factor in the area of ore rock representative has six main factors: F1 respectively. Cr-GaZr-Nb-Hf-Ta-W-Pb-Th, on behalf of the deep dacite porphyry and slate; F2 main factor: LiBe-Sc-Ga-Rb-Zr-Nb-Cs-Hf-Th, trace elements represent terrigenous microclastic rocks; F3 main factor: Co-Ni-Zn-Y-Mo-U, represent the metallogenic period of calcite ore and limestone; F4 main factor: V-Cu-Mo-U, on behalf of silicon rock Stone and ore bearing calcite veins; F5 main factor: Bi-Pb-Ba, sedimentary cherts; F6 main factor: Sr, sedimentary limestone and silicified limestone. The relationship between the F5 factors and F6 factors closely, for the marine chemical sedimentary origin; F2 factor, F3 factor, F4 factor. The more closely related to the mineralization process; F1 factor contrast. These results indicated that mineralization and Metallogenic Significance of siliceous rocks, the average content of siliceous rocks closely.6. silicon limestone and hydrothermal calcite and quartz vein between the area of 10.955 * 10-6 siliceous rocks, uranium and thorium, the average content is only 0.534 * 10-6, Th/U is only 0.059, is a sedimentary uranium rich siliceous rocks is very low. Th/U built the area value may suggest that the rocks in the major U activity of uranium. Therefore, high content of uranium ore containing siliceous rock series in Ruoergai and low Th/U value of uranium mineralization is very favorable, formed by hot water sedimentation The siliceous rocks lay a good material foundation for later mineralization of uranium. Calcification of silicon rocks in this area (limestone) not only large porosity, and prone to brittle deformation and the formation of interlayer fracture zone, favorable ore bearing hydrothermal in migration and precipitation accumulation. So the siliceous rocks are not only favorable source of ore mineralization the calcification of siliceous rocks siliceous rock formed by carbonate (limestone) provides very favorable space for the mineralization. The understanding of the genesis of the deposit of Ruoergai uranium ore field, deepen understanding, has important guiding significance to guide the region's uranium ore prospecting work.

【學位授予單位】：成都理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P619.14;P588.244

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