【摘要】：流變學(xué)實(shí)驗(yàn)表明,當(dāng)巖漿中晶體體積分?jǐn)?shù)達(dá)到約50vol%時(shí),巖漿體實(shí)際上處于凍結(jié)狀態(tài),不再具有整體遷移的能力。但在自然界中仍存在含大量斑晶的淺成火成巖和火山巖。因此,富晶體巖漿的上升過(guò)程和侵位機(jī)制是近年來(lái)地球科學(xué)領(lǐng)域關(guān)注的熱點(diǎn)之一。目前,凍結(jié)巖漿房的活化機(jī)制主要有二種:升溫活化機(jī)制和流體活化機(jī)制。河北武安坦嶺地區(qū)新發(fā)現(xiàn)的多斑斜長(zhǎng)斑巖為揭示凍結(jié)巖漿房的活化提供了契機(jī)。野外觀察和晶體粒度分布(CSD)分析表明,坦嶺斜長(zhǎng)斑巖中斜長(zhǎng)石斑晶高達(dá)70vol%,基質(zhì)為顯微晶質(zhì)結(jié)構(gòu)。斜長(zhǎng)石斑晶粒徑分布均一,大小約為3.1×1.7mm;顯微鏡觀察和背散射圖像揭示,斜長(zhǎng)石斑晶具環(huán)帶結(jié)構(gòu),由寬廣的斜長(zhǎng)石核部+寬度可變的條紋長(zhǎng)石邊部組成,且無(wú)熔蝕現(xiàn)象;電子探針成分剖面分析表明,斑晶核部成分為更長(zhǎng)石(An_(27)Ab_(71)Or_2),幔部為更長(zhǎng)石(An_(13)Ab_(83)Or_4),邊部為條紋長(zhǎng)石。邊部條紋長(zhǎng)石的成分有一定變化,從內(nèi)側(cè)到外側(cè),主晶鈉長(zhǎng)石成分由Ab_(53)Or_(47)變?yōu)锳b_(99)Or_1,客晶鉀長(zhǎng)石成分由Ab_(48)Or_(51)變?yōu)锳b3Or97。斑晶斜長(zhǎng)石核部存在細(xì)長(zhǎng)條狀或斑點(diǎn)狀鉀長(zhǎng)石,且越靠近中心,鉀長(zhǎng)石斑點(diǎn)的數(shù)量越少。這些特點(diǎn)表明,邊部條紋長(zhǎng)石為交代成因。稀土和微量元素分析則顯示,邊部條紋長(zhǎng)石具弱正Eu異常,相對(duì)富集LREE和K、Rb、Ba、Sr等大離子親石元素,虧損Th、Zr、Nb的特點(diǎn)。CSD相關(guān)圖解及以上特征表明,斜長(zhǎng)石斑晶形成于穩(wěn)定,封閉的結(jié)晶環(huán)境,并受到晚期堿交代作用的改造�；|(zhì)主要由微粒鈣質(zhì)角閃石,條紋長(zhǎng)石,石英,鉀長(zhǎng)石和鈉長(zhǎng)石組成,含少量自形-半自形磁鐵礦和鈦鐵礦、磷灰石、榍石、金紅石和鋯石等11種礦物組成。11種礦物相和結(jié)構(gòu)特征暗示基質(zhì)形成于極端不穩(wěn)定的結(jié)晶環(huán)境,與斜長(zhǎng)石斑晶形成條件鮮明對(duì)照。根據(jù)基質(zhì)的礦物組成,推測(cè)形成基質(zhì)的巖漿具有富含K、Na、Fe、Si和揮發(fā)分的特征。這種特征與上述關(guān)于條紋長(zhǎng)石環(huán)邊形成條件的判斷一致。據(jù)此,本文認(rèn)為:產(chǎn)生斜長(zhǎng)石斑晶的巖漿曾經(jīng)在地殼深部作過(guò)長(zhǎng)時(shí)間滯留,導(dǎo)致了斜長(zhǎng)石的穩(wěn)定結(jié)晶,增加了巖漿的粘度和密度,使巖漿處于凍結(jié)狀態(tài);富堿高鐵熔體-流體流的注入大幅降低了巖漿的總粘度,并提高了巖漿的浮力,從而促使凍結(jié)巖漿房迅速活化和上升侵位;同時(shí),富堿高鐵熔體-流體流強(qiáng)烈交代了先存的斜長(zhǎng)石斑晶,使其邊部形成條紋長(zhǎng)石;這種熔體-流體流則在快速排氣,冷卻過(guò)程中迅速結(jié)晶,形成了具有不平衡礦物組合的顯微晶質(zhì)基質(zhì)。在巖漿侵入體較深部位,富堿高鐵熔體-流體經(jīng)歷了很緩慢的固結(jié)過(guò)程,而相分離產(chǎn)生的流體有可能萃取攜帶巖漿中的鐵質(zhì),形成富Fe流體流,后者可能對(duì)區(qū)內(nèi)"鐵礦漿"型鐵礦的形成具有重要的貢獻(xiàn)。
[Abstract]:Rheological experiments show that when the volume fraction of crystals in the magma reaches about 50 vols, the magmatic body is in a frozen state and no longer has the ability to migrate as a whole. But in nature, there are still a lot of porphyry-bearing epigenetic igneous rocks and volcanic rocks. Therefore, the ascending process and emplacement mechanism of rich-crystal magma are one of the hot topics in the field of earth science in recent years. At present, there are two main activation mechanisms of frozen magma chamber: heating activation mechanism and fluid activation mechanism. The newly discovered multi-plagiocline porphyry provides an opportunity to reveal the activation of frozen magma chamber. Field observation and (CSD) analysis of crystal grain size distribution show that the plagioclase porphyry in the Tan-ling plagioclase is as high as 70 vols and the matrix is micrystalline structure. The particle size distribution of plagioclase porphyry is uniform and the size is about 3.1 脳 1.7 mm. Microscopic observation and backscatter images show that plagioclase porphyry has a ring structure, which is composed of striped feldspar edges with variable width of the broad plagioclase core, and has no melting phenomenon. The electron microprobe (EPMA) profile analysis shows that the composition of the macular nucleus is more feldspar (An_ (27) Ab_ (71) Or_2), the mantle is An_ (13) Ab_ (83) Or_4, and the edge is striped feldspar. The composition of edge stripe feldspar changed to a certain extent, from inside to outside, the composition of main crystal albite changed from Ab_ (53) Or_ (47) to Ab_ (99) Or_1, the composition of potassium feldspar changed from Ab_ (48) Or_ (51) to Ab3Or97.. In the core of porphyry plagioclase, there are fine stripe or spotted potash feldspar, and the more close to the center, the less the number of potash feldspar spots. These characteristics indicate that the marginal stripe feldspar is the origin of metasomatism. The analysis of rare earth elements and trace elements showed that the fringed feldspar had weak positive Eu anomaly, relatively enriched in LREE and K\ + Rb\ +\ {} b\} ~ (2 +)\%, etc., and depleted the characteristics of Th,Zr,Nb. The correlation diagram of CSD and the above characteristics showed that, Plagioclase porphyry was formed in a stable and closed crystalline environment and was modified by late alkali metasomatism. The matrix is mainly composed of microcalcareous amphibole, striped feldspar, quartz, potassium feldspar and albite, and contains a small amount of magnetite and ilmenite, apatite, sphene. 11 mineral compositions, such as rutile and zircon, indicate that the matrix was formed in an extremely unstable crystalline environment, in contrast to the porphyry formation conditions of plagioclase. Based on the mineral composition of the matrix, it is assumed that the magma forming the matrix is rich in K ~ (2 +) Na ~ (2 +) Fe ~ (2 +) Si and volatile compounds. This characteristic is consistent with the above judgment on the formation condition of the fringed feldspar ring. Based on this, it is concluded that the magma that produced plagioclase porphyry has been stuck in the deep crust for too long, which leads to the stable crystallization of plagioclase, increases the viscosity and density of magma, and makes the magma freeze; The injection of alkali-rich high iron melt-fluid flow has greatly reduced the total viscosity of magma and increased the buoyancy of magma, thus promoting the rapid activation and emplacement of frozen magma chamber. At the same time, the alkali-rich high iron melt-fluid flow strongly replaced the preexisting plagioclase porphyry, resulting in the formation of striped feldspar at the edge of the plagioclase. The melt-fluid flow is rapidly exhaled and crystallized rapidly during cooling, resulting in a micrystalline matrix with unbalanced mineral assemblage. In the deeper part of the magmatic intrusion, the alkali-rich high iron melt-fluid experienced a very slow consolidation process, while the fluid produced by phase separation may extract the iron from the carrying magma to form the Fe rich fluid. The latter may play an important role in the formation of "iron ore" type iron ore in the region.
【作者單位】： 中國(guó)地質(zhì)大學(xué)地球科學(xué)與資源學(xué)院;中國(guó)黃金集團(tuán)資源有限公司;
【基金】：中國(guó)地質(zhì)調(diào)查局項(xiàng)目(12120115069701) 國(guó)家自然科學(xué)基金項(xiàng)目(41272105) 教育部博士學(xué)科點(diǎn)基金聯(lián)合資助
【分類(lèi)號(hào)】：P588.13

【相似文獻(xiàn)】

相關(guān)期刊論文 前10條

1 Wes Hildreth;薛懷民;;硅質(zhì)巖漿房中的梯度[J];國(guó)外火山地質(zhì);1987年04期

2 A.Gudmundsson ,邱永泉;冰島地殼巖漿房的形成[J];地質(zhì)地球化學(xué);1988年01期

3 Daniel Martin;Ross W.Griffths;Ian H.Campbell;戴愛(ài)華;吳志勤;;巖漿房?jī)?nèi)的成分對(duì)流與熱對(duì)流[J];國(guó)外火山地質(zhì);1989年01期

4 Agust Gudmundsson;林峻;;聚集在巖漿房周?chē)膹垜?yīng)力對(duì)侵入作用和噴出作用頻率的影響[J];國(guó)外火山地質(zhì);1990年03期

5 陶奎元;;巖漿房及其梯度研究現(xiàn)狀與問(wèn)題[J];國(guó)外火山地質(zhì);1991年04期

6 毛建仁;;巖漿房不均一性形成機(jī)理研究現(xiàn)狀的評(píng)述[J];國(guó)外火山地質(zhì);1991年04期

7 L.Civetta;R.Galati;R.Santacroce;王愛(ài)華;;維蘇威巖漿房?jī)?nèi)的巖漿混合與對(duì)流成分分層[J];國(guó)外火山地質(zhì);1991年04期

8 Harald Hagen;Else Ragnhild Neumann;張定源;;應(yīng)用開(kāi)放體系模型模擬巖漿房?jī)?nèi)微量元素的分配[J];國(guó)外火山地質(zhì);1991年02期

9 A.Nicolas;陶魯;;洋脊的巖漿房有多大?[J];海洋地質(zhì)譯叢;1993年03期

10 D.Martin ,R.Nokes ,郭孝明;強(qiáng)對(duì)流巖漿房中晶體的沉淀[J];地質(zhì)地球化學(xué);1990年01期

相關(guān)會(huì)議論文 前3條

1 樊祺誠(chéng);隋建立;李霓;孫謙;;長(zhǎng)白山天池火山雙巖漿房的互動(dòng)式噴發(fā)[A];中國(guó)礦物巖石地球化學(xué)學(xué)會(huì)第11屆學(xué)術(shù)年會(huì)論文集[C];2007年

2 程黎鹿;曾鈴;羅照華;王瑜;;流體再活化部分固化巖漿房的機(jī)制:以峨眉山大火成巖省斜長(zhǎng)石巨晶玄武巖為例[A];中國(guó)地球物理學(xué)會(huì)第二十七屆年會(huì)論文集[C];2011年

3 胡亞軒;王慶良;李克;鄭傳芳;;不同壓力源模型引起的火山區(qū)地面變形特征分析[A];火山作用與地球?qū)尤ρ莼珖?guó)第四次火山學(xué)術(shù)研討會(huì)論文摘要集[C];2005年

相關(guān)重要報(bào)紙文章 前1條

1 孝文;美國(guó)科學(xué)家首次發(fā)現(xiàn)地下巖漿房[N];地質(zhì)勘查導(dǎo)報(bào);2008年

相關(guān)碩士學(xué)位論文 前1條

1 彭年;五大連池新期火山巖漿房的動(dòng)力穩(wěn)定性研究[D];首都師范大學(xué);2004年

，

本文編號(hào)：2316604