發(fā)布時(shí)間：2018-05-09 08:34

  本文選題：結(jié)晶分異作用 + 堆晶作用�。� 參考：《中國(guó)科學(xué):地球科學(xué)》2017年07期

【摘要】：作為大陸地殼的重要組成部分,花崗巖一直是地質(zhì)學(xué)中經(jīng)久不衰的研究課題.從小型巖枝、巖脈,到大型巖基,花崗巖在不同尺度上表現(xiàn)出結(jié)構(gòu)、構(gòu)造、礦物組成及化學(xué)成分的不均一性.對(duì)導(dǎo)致花崗巖成分變異的原因,目前學(xué)術(shù)界則存在不同的認(rèn)識(shí).爭(zhēng)論的焦點(diǎn)在于,花崗巖漿是否能夠發(fā)生有效的結(jié)晶分異作用,以及如果有的話,將發(fā)生何種類型的結(jié)晶分異作用.本文通過資料的歸納與整理認(rèn)為,盡管花崗巖漿由于較高的SiO_2含量導(dǎo)致其較高的粘度,但花崗巖漿的結(jié)晶分異作用既有野外宏觀地質(zhì)資料證據(jù),也有微觀尺度礦物組成及其成分變化的證據(jù),更有大量地球化學(xué)資料的支持.這些資料顯示,單純的重力分異并不是花崗巖漿結(jié)晶分離作用的主導(dǎo)機(jī)制.相反,流動(dòng)導(dǎo)致的分異可能是花崗巖漿成分變異最主要的原因.根據(jù)結(jié)晶分異程度,花崗巖可劃分為低分異花崗巖、高分異花崗巖以及與之伴生的堆晶花崗巖,它們都將是未來(lái)花崗巖巖石學(xué)研究的前沿.在大型巖漿房中,高分異花崗巖的出現(xiàn)主要與它的高溫及富揮發(fā)分相關(guān);而沿伸展構(gòu)造的侵位也是花崗巖漿能夠發(fā)生強(qiáng)結(jié)晶分異作用的重要控制因素.在高度結(jié)晶分異作用情形下,花崗巖漿較長(zhǎng)的結(jié)晶時(shí)間使其極易受到圍巖同化混染的影響.因而,花崗巖在很多情況下并不能反映源區(qū)的特征及巖漿形成的物理化學(xué)條件.從目前的研究來(lái)看,高分異花崗巖有可能是大陸地殼成分成熟度的重要標(biāo)志,且與W、Sn、Nb、Ta、Li、Be、Rb、Cs和REE等稀有金屬成礦作用關(guān)系密切.
[Abstract]:As an important part of continental crust, granite has been an enduring research subject in geology. From small branches, veins to large bedrock, granites show heterogeneity in structure, structure, mineral composition and chemical composition on different scales. At present, there is a different understanding of the causes of granite composition variation. The focus of the debate is whether granitic magma can produce effective crystallization differentiation and, if so, what kind of crystallization differentiation will occur. In this paper, we conclude that although the high SiO_2 content of the granite magma leads to its higher viscosity, the crystallization differentiation of the granite magma is based on the evidence of field macroscopic geological data. There is also evidence of changes in mineral composition and composition at the micro scale, supported by a great deal of geochemical data. These data indicate that pure gravity differentiation is not the dominant mechanism for the crystallization separation of granitic magma. On the contrary, the differentiation caused by flow may be the main reason for the variation of magma composition. According to the degree of crystallization differentiation, granites can be divided into low-differentiated granites, high-grade isomorphic granites and associated heap-grained granites, all of which will be the frontiers of future granite petrology. In large magma chambers, the appearance of high grade isomerite is mainly related to its high temperature and rich volatilization, and emplacement along extensional structure is also an important controlling factor for strong crystallization differentiation of granitic magma. Under the condition of high crystallization differentiation, the granitic magma is easily affected by the assimilation of surrounding rock due to its long crystallization time. Therefore, granite can not reflect the characteristics of the source area and the physical and chemical conditions of magma formation in many cases. According to the present studies, the high grade isomorphic granites may be an important indicator of continental crustal maturity, and are closely related to the mineralization of rare metals such as REE and NbSN.
【作者單位】： 中國(guó)科學(xué)院地質(zhì)與地球物理研究所巖石圈演化國(guó)家重點(diǎn)實(shí)驗(yàn)室;中國(guó)科學(xué)院青藏高原地球科學(xué)卓越創(chuàng)新中心;中國(guó)科學(xué)院大學(xué)地球科學(xué)院;
【基金】：國(guó)家自然科學(xué)基金項(xiàng)目(批準(zhǔn)號(hào):41130313) 中國(guó)科學(xué)院戰(zhàn)略性先導(dǎo)科技B類專項(xiàng)項(xiàng)目(編號(hào):XDB03010200)資助
【分類號(hào)】：P588.121

【參考文獻(xiàn)】

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