本文選題：溧水盆地　切入點(diǎn)：中生代火山巖　出處：《中國(guó)地質(zhì)科學(xué)院》2015年碩士論文

【摘要】：由于強(qiáng)烈的中生代火山活動(dòng),溧水火山構(gòu)造洼地中該期陸相火山巖系廣泛分布。溧水火山構(gòu)造洼地是長(zhǎng)江中下游多金屬成礦帶中眾多火山構(gòu)造洼地之一,也是長(zhǎng)江中下游中生代沿江火山巖帶的重要組成部分。但由于該區(qū)植被和第四系覆蓋極其嚴(yán)重,制約了相關(guān)研究工作的深入開(kāi)展。因此,長(zhǎng)期以來(lái),溧水火山構(gòu)造洼地缺乏系統(tǒng)的年代學(xué)、地球化學(xué)及火山巖巖漿成因?qū)W研究。這一方面制約了對(duì)該火山構(gòu)造洼地中生代火山活動(dòng)的期限、火山巖成因及其巖漿演化過(guò)程的認(rèn)識(shí)；另一方面也制約了對(duì)其龍王山旋回晶屑凝灰?guī)r中的鍶礦床的研究。因此,本文選取了溧水火山構(gòu)造洼地中生代各旋回代表性火山巖地層進(jìn)行了詳細(xì)的野外調(diào)查及路線地質(zhì)剖面觀察,進(jìn)行了系統(tǒng)的鋯石U-Pb年代學(xué)、巖相學(xué)、地球化學(xué)等研究,并在此基礎(chǔ)上建立了該火山構(gòu)造洼地火山活動(dòng)的年代學(xué)格架,探討了火山巖的成因及巖漿演化過(guò)程。另外對(duì)該火山構(gòu)造洼地中最大的鍶礦床愛(ài)景山鍶礦進(jìn)行了重砂、礦物原位微區(qū)分析、包裹體成分、溫度、鹽度等研究,從而初步探討了該區(qū)鍶礦床的物質(zhì)來(lái)源及鍶富集機(jī)制。 鋯石LA-ICPMS U-Pb定年分析測(cè)得溧水火山構(gòu)造洼地龍王山旋回火山巖形成于135～132Ma：大王山旋回火山巖形成于132-125Ma,姚家邊旋回火山巖形成于130～128Ma之后該區(qū)大規(guī)模的火山活動(dòng)基本終止并進(jìn)入長(zhǎng)期沉寂期,最晚期甲山旋回火山巖形成于110Ma,火山活動(dòng)結(jié)束。火山巖鋯石年代學(xué)研究結(jié)果表明溧水火山構(gòu)造洼地中生代火山巖均形成于早白堊世,其主體火山活動(dòng)時(shí)間與長(zhǎng)江中下游其它火山構(gòu)造洼地火山巖的形成時(shí)代一致(135～124Ma)。溧水火山構(gòu)造洼地火山巖含一套具有正常演化序列的基性-中酸性-酸性火山巖及其火山碎屑巖,其中以基性-中酸性為主。巖石普遍具有富堿、富鉀、富集輕稀土元素及大離子親石元素K、Rb、 Ba、Th、U,明顯虧損高場(chǎng)強(qiáng)元素Nb、Ta、Ti的特征。并具有高87Sr/86Sr初始比值(0.705604-0.707080)、負(fù)εNd(t)(-2～-9)、負(fù)εNd(t)(-4--13)的同位素特征。綜上分析,筆者認(rèn)為溧水火山巖巖漿來(lái)源于殼源熔體/流體交代的巖石圈富集地幔,并在巖漿上升過(guò)程中有地殼物質(zhì)的混染及單斜輝石、角閃石、磷灰石等礦物的分離結(jié)晶,其中中基性巖漿遭遇地殼物質(zhì)混染及分異作用程度較低。 愛(ài)景山鍶礦天青石中鋯石年齡復(fù)雜,包含了太古代、元古代、印支期及加里東期多組年齡,顯示基底地層對(duì)鍶礦成礦物質(zhì)具有一定的貢獻(xiàn)。溧水地區(qū)龍王山旋回火山巖具有較高的鍶含量(平均為965×10-6),其它旋回火山巖的鍶含量較低(512×10-6、164×10-6～315×10-6、和338×10-6～389×10-6)。結(jié)合前人測(cè)得的鍶礦區(qū)基底地層及富礦圍巖鍶含量及硫同位素?cái)?shù)據(jù),筆者認(rèn)為鍶來(lái)源于龍王山旋回晶屑凝灰?guī)r,同時(shí),安山玢巖也可能是其源巖之一；硫主要來(lái)源于該盆地基底地層周沖村組膏巖層。龍王山組火山巖具有較下地殼和地幔稍高的Rb/Sr比值(0.21-0.31)和高的Sr含量(609×10-6～1140×10-6))以及富礦晶屑凝灰?guī)r中大量斜長(zhǎng)石(含量達(dá)60%)的存在,筆者分析認(rèn)為地殼的混染不是鍶富集的主導(dǎo)原因,斜長(zhǎng)石的分離結(jié)晶作用可能是導(dǎo)致鍶元素富集的主要原因。 通過(guò)天青石流體包裹體的成分、溫度、鹽度分析結(jié)果顯示流體包裹體的成分以CO2、CO、H2、 N2成分為主,并含有少量的H2S、CH4等,液相以H20為主。天青石流體包裹體溫度變化于240-360℃之間,鹽度多變化于0.5-6.5%之間。結(jié)合鍶礦體的地質(zhì)特征,初步分析認(rèn)為初步分析認(rèn)為溧水愛(ài)景山鍶礦鍶的富集機(jī)制為火山熱液,同時(shí)不排除地下熱泉對(duì)鍶的富集作用。
[Abstract]:Due to the strong Mesozoic volcano activity, the continental volcano rocks of Lishui volcano tectonic depression are widely distributed in Lishui. The volcano tectonic depression of Yangtze River is a polymetallic metallogenic belt in one of the many volcano tectonic depression is a Mesozoic volcano rocks along the Yangtze River, the Yangtze River with the important part. But because of the vegetation and Quaternary Cover extremely seriously, restricted the related research work carried out in-depth. Therefore, for a long time, the Lishui volcano tectonic depression and lack of systematic study on geochronology, geochemistry and volcano magma origin. This restricts the volcano tectonic depression Mesozoic volcano activity period, volcano rock formation and understanding of magma evolution; on the other hand also restricted the research of the Longwangshan strontium deposit cycles in crystal tuff. Therefore, this paper selects the Lishui volcano tectonic depression during every rotation Back to the representative of the volcano rock formation were observed and detailed field investigation and geological profile, the zircon U-Pb chronology, the petrography, geochemistry, and established the geochronological framework of the volcano tectonic depression volcano activity, discusses the origin and evolution of magma and volcano rock. In addition to the the volcano tectonic depression in strontium deposit, the greatest love of Jingshan Hill strontium ore placer, in-situ analysis of mineral inclusions, body composition, temperature, salinity and so on, so as to investigate the strontium deposit in this area of the material source and strontium enrichment mechanism.
Zircon LA-ICPMS U-Pb dating of measured Lishui volcano tectonic depression Longwangshan cycle volcano rocks formed in 135 ~ 132Ma: dawangshan cycle volcano rocks formed in the 132-125Ma, Yao Jia Bian cycled volcano rocks formed in 130 ~ 128Ma after the massive volcano activities cease to long period of silence, the most advanced cycle of a mountain volcano rock formed in the 110Ma end of the event. The volcano volcano rock zircon geochronology indicates that the Lishui volcano tectonic depression Mesozoic volcano rocks were formed in the early Cretaceous, the volcano activity time and the lower reaches of other volcano structure formation, consistent with the age of fire made wa rock (135 ~ 124Ma). A set of basic and normal evolution sequence in the intermediate acidic volcano rock and volcano clastic rocks containing Lishui volcano tectonic depression volcano rock, in which basic to intermediate acid rock. Generally with alkali, potassium rich, rich in Light rare earth elements and large ion lithophile elements K, Rb, Ba, Th, U, significantly depleted in high field strength elements Nb, Ta, Ti and 87Sr/86Sr. Features with high initial ratio (0.705604-0.707080), negative epsilon Nd (T) (-2 ~ -9), epsilon negative (T) Nd (-4--13). Isotope analysis. To sum up, the author believes that the Lishui volcano magma derived from crust derived melt / fluid metasomatic lithosphere mantle enrichment, and the contamination during magma ascent and clinopyroxene, crustal amphibole, apatite mineral separation and crystallization, which in the magma crust material contamination and encounter differentiation degree is relatively low.
Love the Jingshan Hill of Strontium in celestite zircon age complex contains Archean, Proterozoic, Caledonian and Indosinian age group, indicates that the basal formation has some contribution to strontium ore forming materials. Strontium content Longwangshan cycle volcano rocks in the Lishui area has high (the average is 965 x 10-6), strontium content of other cycles volcano rock is low (512 * 10-6164 * 10-6 ~ 315 * 10-6 and 338 * 10-6 ~ 389 * 10-6). Combined with previous measured strontium mine basement strata and ore rock and sulfur content of strontium isotope data, the author thinks that the strontium from Longwangshan cycle crystal tuff, and andesitic porphyrite may is one of the main sources of sulfur source rocks; the basin basement strata of Zhou Chong village. Gypsum rocks volcano rock mountain dragon group has a lower Rb/Sr ratio of crust and mantle slightly higher (0.21-0.31) and high Sr content (609 * 10-6 ~ 1140 * 10-6)) and rich crystal coagulation The existence of massive plagioclase (content 60%) in limestone indicates that the mixing of the crust is not the leading cause of strontium enrichment. The separation and crystallization of plagioclase may be the main reason for the enrichment of strontium.
The celestite fluid inclusion composition, temperature, salinity analysis results showed that the fluid inclusion composition by CO2, CO, H2, N2 components, and contains a small amount of H2S, CH4, H20 in liquid phase. Celestite fluid inclusions temperature change to 240-360 DEG, salinity changes between 0.5-6.5% with multi. The geological characteristics of strontium ore, preliminary analysis that the preliminary analysis that the enrichment mechanism of Lishui love Jingshan Hill for strontium strontium ore volcano hydrothermal, and does not exclude the enrichment of underground hot springs of strontium.

【學(xué)位授予單位】：中國(guó)地質(zhì)科學(xué)院
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：P317;P618.78

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