發(fā)布時(shí)間：2018-05-23 12:41

  本文選題：年代學(xué) + Hf同位素��； 參考：《吉林大學(xué)》2016年碩士論文

【摘要】：研究區(qū)在地理位置上位于大興安嶺北段東坡,在大地構(gòu)造位置上位于興蒙造山帶東段的興安地塊內(nèi)。本文通過對(duì)紅花爾基地區(qū)古生代花崗質(zhì)巖石的鋯石U Pb年代學(xué)、元素地球?qū)W及鋯石Hf同位素特征的研究,確定了古生代花崗巖的形成時(shí)代,分析了古生代花崗巖的巖石學(xué)和地球化學(xué)特征,探討了古生代花崗巖的巖漿源區(qū)性質(zhì)、巖石成因以及形成時(shí)的構(gòu)造背景,其成果對(duì)于揭示大興安嶺地區(qū)大地構(gòu)造演化具有一定意義。筆者從研究區(qū)古生代花崗巖中選取了2個(gè)樣品,對(duì)其進(jìn)行了LA-ICP-MS鋯石U-Pb同位素年齡的測(cè)定,樣品中的鋯石具有振蕩生長(zhǎng)環(huán)帶和較高的Th/U比值,揭示其巖漿成因,可以反映巖石的形成時(shí)代。通過分析測(cè)試可將紅花爾基地區(qū)古生代花崗巖劃分為早石炭世堿長(zhǎng)花崗巖(348.9±2.1 Ma)與晚石炭世二長(zhǎng)花崗巖(310.5±1.3 Ma)兩期。早石炭世堿長(zhǎng)花崗巖主量元素具有高SiO2,富K2O,TFeO值高,貧Al2O3,貧MgO,貧CaO的特征;稀土配分呈現(xiàn)具強(qiáng)烈負(fù)銪異常的“海鷗型”分布型式;微量元素蛛網(wǎng)圖上呈現(xiàn)富集Rb、Th、U、K和強(qiáng)烈虧損Ba、Sr、P、Ti的特點(diǎn);鋯石飽和溫度高,在花崗巖成因判別圖解中落入A型花崗巖區(qū)域,具有A型花崗巖的特征。晚石炭世二長(zhǎng)花崗巖具有高SiO2,高Na2O,低P2O5的特征,且其P2O5含量隨著SiO2含量的升高而下降;除兩個(gè)樣品的鋁飽和指數(shù)ACNK略大于1.1外,其余樣品的鋁飽和指數(shù)均小于1.1,鋯石飽和溫度低于典型A型花崗巖的形成溫度(850℃),在花崗巖成因判別圖解中落入分異的I型花崗巖區(qū)域,具有I型花崗巖的特征。結(jié)合正的εHf(t)值和二階段模式年齡判斷研究區(qū)古生代花崗巖來源于中新元古代從虧損地幔中新增生來的地殼物質(zhì)的部分熔融。結(jié)合構(gòu)造判別圖解、同時(shí)代大興安嶺地區(qū)花崗巖特征及區(qū)域構(gòu)造背景可判斷紅花爾基地區(qū)古生代花崗巖形成于興安地塊與松嫩地塊碰撞伸展的轉(zhuǎn)換過程中。
[Abstract]:The study area is located in the eastern slope of the northern Daxing'an Mountains and in the Xingan block in the eastern part of the Xingmeng orogenic belt. Based on the study of U-Pb zircon dating, elemental geology and zircon HF isotopic characteristics of Paleozoic granitic rocks in the Honghuaerji area, the formation age of Paleozoic granites has been determined in this paper. The petrological and geochemical characteristics of Paleozoic granites are analyzed, and the magmatic origin, petrogenesis and tectonic setting of Paleozoic granites are discussed. The results are of significance for revealing the tectonic evolution in the Daxinganling area. Two samples were selected from Paleozoic granites in the study area and their LA-ICP-MS zircon U-Pb isotopic ages were determined. The zircon in the sample has oscillating growth ring and high Th/U ratio, which reveals the magmatic origin. It can reflect the age of rock formation. The Paleozoic granites in the Honghuaerji area can be divided into two periods: early Carboniferous alkali feldspar granite (348.9 鹵2.1 Ma) and late Carboniferous monzogranite (310.5 鹵1.3 Ma). The main elements of the early Carboniferous alkali feldspar granite are characterized by high SiO2, high K _ 2O-rich TFeO value, poor Al _ 2O _ 3, poor MgO and poor CaO, and the rare earth distribution shows a "seagull type" distribution pattern with strong negative europium anomaly. The trace element cobwebs show the characteristics of enrichment of RbSH-UUK and strong depletion of Bao-Sr-Pa-Ti, and the high saturation temperature of zircon, which falls into A-type granite area in the diagenetic diagram of granite genesis, and has the characteristics of A-type granite. The late Carboniferous monzogranite has the characteristics of high Sio _ 2, high Na _ 2O and low P2O5, and its P2O5 content decreases with the increase of SiO2 content, except for two samples, the Al saturation index (ACNK) is slightly greater than 1.1. The aluminum saturation index of the other samples is less than 1.1, and the zircon saturation temperature is lower than the formation temperature of typical A-type granite at 850 鈩，

本文編號(hào)：1924789