本文選題：東馬努斯盆地 + 高鎂安山巖　； 參考：《中國科學(xué)院大學(xué)(中國科學(xué)院海洋研究所)》2017年碩士論文

【摘要】：本文使用水下機(jī)器人獲取了東馬努斯盆地的玄武質(zhì)安山巖、英安巖和熱液蝕變巖石樣品,通過對樣品進(jìn)行全巖主微量、Sr-Nd-Pb同位素和斜長石電子探針分析,并結(jié)合前人數(shù)據(jù),發(fā)現(xiàn)了該區(qū)一直被忽視的高鎂安山巖,探究了巖漿物質(zhì)來源及熱液活動(dòng)中元素的遷移規(guī)律。東馬努斯盆地的2個(gè)玄武質(zhì)安山巖樣品具有高鎂含量,其MgO含量分別為5.3%和5.54%,FeOT含量分別為8.35%和8.22%,FeOT/MgO比值分別為1.575和1.484,Al2O3含量分別為15.77%和15.82%,CaO含量分別為9.22%和9.28%,屬于高鎂安山巖。東馬努斯盆地是一個(gè)活躍的弧后盆地,伴隨著太平洋板塊和所羅門板塊雙重俯沖的影響,俯沖物質(zhì)來源存在爭議。有學(xué)者認(rèn)為俯沖物質(zhì)來自于太平洋板塊,也有學(xué)者認(rèn)為來自于所羅門板塊。本文首先通過巖漿中具有Pb和大離子親石元素(K,Rb,Sr,Ba,和U)富集、高場強(qiáng)元素(Nb,Th,Ta和Ti)虧損的特征,證實(shí)了俯沖板塊脫水作用產(chǎn)生了大量的含水物質(zhì)注入到巖漿源區(qū)。再由87Sr/86Sr比值沿太平洋板塊俯沖方向連續(xù)變化和238U過剩的現(xiàn)象證明巖漿受到了太平洋板塊和所羅門板塊雙重俯沖的影響,并且,太平洋板塊物質(zhì)在東馬努斯盆地滯留了很長一段時(shí)間,而所羅門板塊物質(zhì)是最近才加入的。高鎂安山巖由地幔橄欖巖演化而來,地幔橄欖巖的同位素特征與馬努斯MORB一致;俯沖板塊物質(zhì)包含了海底沉積物和蝕變洋殼,因此,東馬努斯巖漿物質(zhì)來源可能包括:馬努斯MORB、太平洋和所羅門板塊的海底沉積物和蝕變洋殼。如果這5個(gè)端元都對東馬努斯巖漿有貢獻(xiàn),那么計(jì)算可得,太平洋蝕變洋殼與沉積物的比值為86.5:13.5,這二者的總含量與馬努斯MORB的比值為8.2:91.8,所羅門蝕變洋殼與沉積物的比值為93.5:6.5,在馬努斯MORB含量不變的情況下,每增加一份太平洋俯沖物質(zhì),需要增加9份所羅門俯沖物質(zhì)來與之平衡。文章還對蝕變巖石與新鮮火山巖之間的全巖主微量及斜長石電子探針數(shù)據(jù)進(jìn)行對比,深入探究了蝕變火山巖的元素遷移特征及影響因素。結(jié)果顯示,蝕變火山巖的硫化物以黃銅礦、方鉛礦和閃鋅礦為主,為富Cu型熱液硫化物。巖石蝕變區(qū)的SiO2含量極高,為硅化蝕變。蝕變巖石的化學(xué)成分約為同區(qū)玄武質(zhì)安山巖和英安巖成分總含量的平均值,原巖可能為安山巖。在熱液蝕變的過程中,蝕變巖石的質(zhì)量增加了150%,其中元素Cu、Zn、Ga、Sr、Cd、Ba和Pb超強(qiáng)烈富集,Ti、V、Mn、Co、Ni、Mo和U強(qiáng)烈富集,Si和Fe中等富集;Sc、Cr、Nb、Ta、W和Bi輕微富集;Be和Ca超強(qiáng)烈虧損;Li、Na、Mg、K、Rb、REE和Y強(qiáng)烈虧損;Zr、Cs和Th輕微虧損;Al、P和Hf穩(wěn)定不變。推測影響蝕變巖石元素遷移的因素有3種:成礦作用、交代作用(綠泥石化、硅化)和元素在流體中的活動(dòng)性。
[Abstract]:In this paper, the samples of Black Tortoise andesite, dolomite and hydrothermal alteration rock from the East Manus Basin were obtained by using underwater vehicle. The samples were analyzed by the main trace Sr-Nd-Pb isotopes and plagioclase electron probe analysis of the whole rock, and combined with previous data. The high mafic andesite which has been neglected in this area has been discovered, and the source of magmatic material and the law of element migration in hydrothermal activity have been explored. The two samples of Black Tortoise andesite in East Manus Basin have high magnesium content, their MgO contents are 5.3% and 5.54%, respectively, and the content of FeOT / MgO are 8.35% and 8.22%, respectively. The ratios of Al _ 2O _ 3 _ 2O _ 3 and Al _ 2O _ 3 are 15.77% and 15.82%, respectively, and 9.28% and 9.28, respectively, which belong to the high mafic andesite. The East Manus Basin is an active back-arc basin. With the influence of the double subduction of the Pacific plate and the Solomon plate, the subduction material source is controversial. Some scholars believe that the subduction material comes from the Pacific plate, and others think it comes from the Solomon plate. In this paper, the characteristics of Pb and large ion lithophile element K ~ (+) Rb ~ (+) Sr ~ (+) Baand U) and the depletion of high field strength elements such as NB ~ (2 +) T _ (Th) Ta and Ti) in magma have proved that dehydration of subduction plate resulted in a large amount of water-bearing material being injected into the magma source region. The continuous variation of the 87Sr/86Sr ratio along the subduction direction of the Pacific plate and the phenomenon of 238U excess prove that the magma is affected by the double subduction of the Pacific plate and the Solomon plate. Pacific plate material remained in the East Manus Basin for a long time, and Solomon Plate material was only recently added. The high-mafic andesite evolved from the mantle peridotite, and the isotopic characteristics of the mantle peridotite are consistent with those of Manus MORB. Sources of East Manus magmatic material may include: Manus MORBB, seabed sediments and altered oceanic crust in the Pacific and Solomon plates. If all five end elements contribute to the East Manus magma, then the calculations are available. The ratio of altered oceanic crust to sediment in the Pacific Ocean is 86.5: 13.5.The ratio of total content of these two to Manus MORB is 8.2: 91.8, and the ratio of Solomon altered oceanic crust to sediment is 93.5: 6.5. Under the condition of constant MORB content in Manus, each Pacific subduction material is added. Nine more parts of Solomon's subduction material are needed to balance it. The electron probe data of major trace and plagioclase between altered rocks and fresh volcanic rocks are compared, and the characteristics of element migration and influencing factors of altered volcanic rocks are discussed. The results show that the sulfides of altered volcanic rocks are mainly chalcopyrite galena and sphalerite and are Cu-rich hydrothermal sulfides. The content of SiO2 in rock alteration zone is very high, which is silicified alteration. The chemical composition of altered rocks is about the average of the total contents of Black Tortoise andesite and dolomite in the same area, and the original rock may be andesite. In the process of hydrothermal alteration, The quality of altered rocks has increased by 150, in which the ultrastrong enrichment of Cu ~ (2 +) Zn ~ (Zn) Ga _ (Sr) CD ~ (2 +) Ba and Pb ~ (2 +) ~ (2 +) ~ (2 +) Ti ~ (2 +) V ~ (2 +) mn ~ (2 +) Co ~ (2 +) Mo ~ (2 +) and U ~ (2 +) enriched Si ~ (2 +) and Fe ~ (2 +) ~ (2 +) Cr ~ (2 +) C ~ (2 +) and Fe ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2 +) ~ (2)? It is inferred that there are three factors influencing the element migration of altered rocks: mineralization metasomatism (green mud fossilization silicification) and the activity of elements in fluid.
【學(xué)位授予單位】：中國科學(xué)院大學(xué)(中國科學(xué)院海洋研究所)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：P588.1

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 楊寶菊;曾志剛;殷學(xué)博;王曉媛;陳帥;黃鑫;榮坤波;馬瑤;;PACMANUS熱液區(qū)Fe-Si-Mn羥基氧化物的成因及地球化學(xué)特征[J];海洋地質(zhì)與第四紀(jì)地質(zhì);2016年03期

2 祁冬梅;周漢文;宮勇軍;熊索菲;賈耽;張金;張e鹲，

本文編號(hào)：1866007