岩床
![](http://upload.wikimedia.org/wikipedia/commons/thumb/f/f1/The_difference_between_a_sill_and_a_dike.jpg/260px-The_difference_between_a_sill_and_a_dike.jpg)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/Edinburgh_Salisbury_Crags_2004-05-18.jpg/260px-Edinburgh_Salisbury_Crags_2004-05-18.jpg)
在地质学中,岩床(sill)是一种侵入在更老沉积岩层、火山熔岩或凝灰岩层之间,或沿变质岩叶理方向侵入的板状侵入体。“岩床”是一种整合型侵入岩层,意味着岩床不会穿过原先已存在的岩层。在高岩浆通量情况下,岩床的堆积将构建成一座岩床复合体[1]和大型岩浆房[2]。相较之下,岩脉则是一种穿过了更古老岩石的非整合型侵入岩板。岩床由岩脉供给岩浆[3],除非在特殊位置,它们形成于直接与岩浆源相连的近垂直岩层中。岩石必须是脆性和断裂的,以便能形成岩浆侵入母岩体的平面,无论是沿沉积层或火山层之间原先存在的平面,还是变质岩中与叶理相关的脆弱平面,这些平面或弱化区域可使薄片状岩浆体的侵入平行于现存的层面、整合型断裂带或叶理。
岩床平行于周围原岩中的岩层和叶理,虽然构造作用可能导致水平岩床随后向近垂直方向旋转,但它们最初可能以水平方向分布。岩床可能会与凝固熔岩流相混淆,但它们之间也有数种不同之处。侵入的岩床将显示周围原岩的部分熔化和融合,在岩床所侵入原岩的两侧接触面,能观察到加热的迹象(接触变质作用),而熔岩流只显示在较低一侧的证据。此外,熔岩流通常会显示有气体逸出到大气中的孔状结构(气泡)。而岩床因形成于地表以下,即使通常在较浅的深度(最多数公里)[4],上覆岩石的压力意味着岩床中几乎不会形成气泡。熔岩流的表面通常也会有风化迹象,而岩床如果仍被原岩覆盖,则通常不会。
伴生矿床
[编辑]某些层状侵入体通常包含有各种重要矿物的岩床,前寒武纪的示例有南部非洲布什维尔德火成杂岩(Bushveld Igneous Complex)、因西兹瓦(Insizwa)等轴铋铂矿、“大岩墙”(GreatDyke)铬铁矿,美国苏必利尔地区的德卢斯侵入杂岩(Duluth Complex)和斯蒂尔沃特县火成杂岩;显生宙的岩床通常较小且复杂包括苏格兰拉姆岛的橄榄岩杂岩[5]和格陵兰岛东部斯卡尔加德火成岩杂岩(Skaergaard igneous complex),这些侵入体通常含有一定丰度的金、铂、铬和其他稀有元素。
海侵岩床
[编辑]![](http://upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Sills_in_Rockall_Trough.jpg/256px-Sills_in_Rockall_Trough.jpg)
尽管本质上是整合的,但许多大型岩床侵入层序内的地层水平已发生改变,侵入体的每个整合部分都由相对较短的墙状岩段连接起来。此类岩床被称为“海侵”岩床,例如暗色岩床(Whin Sill)和卡鲁盆地(Karoo basin)内的岩床[6][7]。随着3D地震反射数据的使用,沉积盆地中大型岩床复合体的几何结构变得越发清晰[8]。这些数据表明,许多岩床整体呈碟形,其他许多岩床至少已部分海侵[9]。
另请查看
[编辑]参考资料
[编辑]- ^ Leuthold J.; Müntener O.; Baumgartner L.; Putlitz B. Petrological constraints on the recycling of mafic crystal mushes and intrusion of braided sills in the Torres del Paine Mafic Complex (Patagonia). Journal of Petrology. 2014, 55 (5): 917–949. Bibcode:2014JPet...55..917L. doi:10.1093/petrology/egu011. hdl:20.500.11850/103136
..
- ^ Annen C.; Blundy J.D.; Leuthold J.; Sparks R.S.J. Construction and evolution of igneous bodies: Towards an integrated perspective of crustal magmatism. Lithos. 2015, 230: 206–221. Bibcode:2015Litho.230..206A. doi:10.1016/j.lithos.2015.05.008.
- ^ Meade, F. C.; Chew, D. M.; Troll, V. R.; Ellam, R. M.; Page, L. M. Magma Ascent along a Major Terrane Boundary: Crustal Contamination and Magma Mixing at the Drumadoon Intrusive Complex, Isle of Arran, Scotland. Journal of Petrology. 2009-12-01, 50 (12): 2345–2374. ISSN 0022-3530. doi:10.1093/petrology/egp081
.
- ^ Bell, B.; Butcher, H. On the emplacement of sill complexes: evidence from the Faroe-Shetland Basin. Geological Society, London, Special Publications. 2002, 197 (1): 307–329. Bibcode:2002GSLSP.197..307B. S2CID 128669544. doi:10.1144/GSL.SP.2002.197.01.12.
- ^ Emeleus, C. H.; Troll, V. R. The Rum Igneous Centre, Scotland. Mineralogical Magazine. 2014-08-01, 78 (4): 805–839 [2021-11-04]. Bibcode:2014MinM...78..805E. ISSN 0026-461X. doi:10.1180/minmag.2014.078.4.04
. (原始内容存档于2021-11-06) (英语).
- ^ Hamilton M.A.; Pearson D.G. Srivastava R. , 编. Precise U-Pb Age for the Great Whin Dolerite Complex, N.E. England and Its Significance. Dyke Swarms: Keys for Geodynamic Interpretation (Springer Science & Business Media). 2011 [2021-11-04]. ISBN 9783642124969. (原始内容存档于2021-11-04).
- ^ Polteau S.; Mazzini A.; Galland O.; Planke S.; Malthe-Sørenssen A. Saucer-shaped intrusions: Occurrences, emplacement and implications. Earth and Planetary Science Letters. 2008, 266 (1–2): 195–204. Bibcode:2008E&PSL.266..195P. doi:10.1016/j.epsl.2007.11.015.
- ^ Thomson K.; Hutton D. Geometry and growth of sill complexes: insights using 3D seismic from the North Rockall Trough. Bulletin of Volcanology. 2004, 66 (4): 364–375. Bibcode:2004BVol...66..364T. S2CID 128713713. doi:10.1007/s00445-003-0320-z.
- ^ Planke S.; Rasmussen T.; Rey S.S.; Myklebust R. Doré A.G.; Vining B.A. , 编. Seismic characteristics and distribution of volcanic intrusions and hydrothermal vent complexes in the Vøring and Møre basin. Petroleum geology: north-west Europe and global perspectives : proceedings of the 6th petroleum geology conference held at the Queen Elizabeth II Conference Centre, London 6–9 October 2003. 20052005. ISBN 9781862391642.