發(fā)布時間：2018-04-29 06:41

  本文選題：福建馬坑鐵礦 + 成礦地質(zhì)體�。� 參考：《中國地質(zhì)大學(xué)(北京)》2015年碩士論文

【摘要】：馬坑鐵礦位于福建省龍巖市,是閩西南晚古生代永梅拗陷成礦帶中的大型磁鐵礦床,其成因的破解對于成礦帶上其他具“馬坑式”矽卡巖特征的礦床勘探具有巨大意義。盡管研究工作已相對成熟,但其成因?qū)W者們始終未能得出統(tǒng)一結(jié)論。本文在收集、總結(jié)前人資料的基礎(chǔ)上,通過野外調(diào)查、數(shù)據(jù)分析,認(rèn)為馬坑鐵礦賦礦層位主要為P1j-q(下二疊統(tǒng)經(jīng)畬-棲霞組)灰?guī)r與C1l(下石炭統(tǒng)林地組)砂巖的硅鈣界面之間。礦體形態(tài)受構(gòu)造控制明顯,呈層狀、似層狀,賦存于馬坑背斜虛脫空間中。礦區(qū)中存在由輝綠巖至大理巖所形成的內(nèi)-外矽卡巖巖性剖面,自輝綠巖開始向兩側(cè)依次出現(xiàn)蝕變輝綠巖→矽卡巖化輝綠巖→榴石透輝石矽卡巖→榴石透輝石磁鐵礦→大理巖。局部能見到更復(fù)雜矽卡巖礦物如透閃石、陽起石、符山石、鈣薔薇輝石等,但分帶性較弱。磁鐵礦與石榴子石與透輝石等矽卡巖共生,與大理巖接觸界線截然并靠大理巖一側(cè)存在流體逃逸構(gòu)造。輝鉬礦以浸染狀或者裂隙充填的形式存在于林地組砂巖或輝綠巖中,形成晚于磁鐵礦。最新榴石Sm-Nd等時線年齡顯示成礦在160Ma左右,而被認(rèn)為與成礦相關(guān)的大洋、莒舟花崗巖的鋯石U-Pb年齡范圍在120-155Ma,盡管沒有對應(yīng)160Ma的輝綠巖,由成礦專屬性看來,富鐵流體與基性巖漿來自深源地幔,鉬礦由殼源巖石滲濾富集。因此輝綠巖作為馬坑鐵礦的致礦母巖,形成典型的矽卡巖蝕變分帶,而大洋、莒舟花崗巖帶來后期鉛鋅鉬礦化,其巖漿熱液在一定程度上對礦區(qū)進(jìn)行疊加改造,如第二期的矽卡巖礦物細(xì)脈,林地組石英砂巖硅化等。由觀察研究可知,礦體與輝綠巖直接接觸,而與花崗巖基相隔林地組地層。本文認(rèn)為由于古太平洋板塊的俯沖作用,福建龍巖處于活動大陸邊緣環(huán)境,俯沖的洋殼隨深度加大便發(fā)生脫水作用,揮發(fā)分進(jìn)入上覆地幔楔發(fā)生注水熔融,形成馬坑輝綠巖的原生巖漿,巖漿上升至上地殼形成巖漿房,經(jīng)歷一定程度AFC作用,隨著推覆作用進(jìn)行,地層皺褶破裂,由于壓力驟降,巖漿侵位在礦區(qū)以巖脈形式產(chǎn)出,同時幔源的富鐵高溫高鹽度流體與輝綠巖共享巖漿通道,上升至硅鈣界面,由于與灰?guī)r發(fā)生化學(xué)反應(yīng)沉淀出矽卡巖礦物與磁鐵礦�；詭r漿上升至殼幔邊界加熱下地殼熔融得花崗質(zhì)巖漿,在140Ma左右,下地殼花崗質(zhì)巖漿沿不同巖漿通道侵位,形成大洋、莒舟花崗巖,空間上不與鐵礦接觸,而呈托舉形式。
[Abstract]:Ma Keng iron mine, located in Longyan, Fujian Province, is a large magnet deposit in the metallogenic belt of the late Paleozoic Yong Mei depression in the south of Fujian Province. Its causes are of great significance to the exploration of other ore deposits with the characteristics of "pits" skarn in the metallogenic belt. Although the research has been relatively mature, its genetic scholars have not been able to draw a unified conclusion. On the basis of collecting and summarizing the previous data, through field investigation and data analysis, it is believed that the ore bearing strata of Ma Keng iron ore are mainly between P1j-q (the lower two series of the she Qixia formation) limestone and the silico calcium interface of the sandstone of C1l (Lower Carboniferous woodland group). The form of ore body is controlled obviously, and is layered and layered, and exists in the deficiency of Ma Keng anticline. There is a lithologic section of the inner and outer skarn formed by diabase to marble. From the beginning of the diabase to both sides, the altered diabase, skarite diabase, eclogite diopside skarn, eclogite diopside magnetite and marble were appeared on both sides of the diabase. The more complex skarn minerals such as dioptite, Yang Qishi, were found in the region. It is found that the magnetite and pomegranite are symbiotic with diopside rocks such as diopside, and the boundary between the marble and the marble is obvious and there is a fluid escape structure on the marble side. The molybdenite is found in the form of the sandstone or diabase in the form of the marbles or the form of the diopter or fissures, which is later than the magnetite. The age of the stone Sm-Nd isochronous line shows that the mineralization is around 160Ma, and the zircon U-Pb age of the Junzhou granite is considered to be in 120-155Ma, although there is no 160Ma corresponding to the diabase, the rich iron fluid and basic magma are derived from the deep source mantle, and the molybdenum ore is enriched by the shell source rock. A typical skarn alteration zone is formed for the ore-forming parent rock of Ma Keng iron ore, while in the ocean, Junzhou granite brings late lead, zinc and molybdenum mineralization, and its magmatic hydrothermal solution is superimposed on the mining area to a certain extent, such as the second phase skarn mineral vein and the silicified quartz sandstone in the woodland group. In this paper, the subduction of the paleopacific plate in Fujian Longyan is situated on the active continental margin, and the subducted oceanic crust is dehydrated with depth and stool, and the volatile matter enters the overlying mantle wedge with water injection melting, forming the primary magma of the horse pit and the magma up to the upper ground. The crust formed a magma chamber and experienced a certain degree of AFC action. With the push of nappe, the formation folds ruptured, because of the sudden pressure drop, the magma emplacement produced in the form of rock veins in the mining area. At the same time, the mantle derived iron rich high temperature high salinity fluid shared the magma channel with the diabase, rising to the calcium silicate interface, and precipitated the skarn with the chemical reaction with the limestone. Minerals and magnetite. The crust of basic magma rises to the crust and mantle boundary to melt the granitic magma. At about 140Ma, the granitic magma of the lower crust emplacement along different magma channels, forming the ocean and Junzhou granite, which is not in contact with the iron ore in space, but in the form of lifting.

【學(xué)位授予單位】：中國地質(zhì)大學(xué)(北京)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：P618.31

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