藩市杂岩(英語:Franciscan complex) 是指在美國加利福尼亚州海岸山脉的混杂沉积(英語:melange[1]。 它的組成以輕度变质的杂砂岩(英語:graywacke)、页岩和砾岩为主,並夾有燧石、玄武岩、石灰岩、蛇纹岩,以及高压、低温变质的蓝片岩和榴辉岩[2][3]。 藩市杂岩基本是由变质和变形岩石的组合,它的成因与北美西海岸的中生代东倾俯冲带有关[4]。当时加利福尼亚大陆边缘存在一条中生代深海海沟。这条海沟是中生代的法拉隆(英語:Farallon)洋壳板块,向北美大陆板块俯冲造成的。首先洋底玄武岩和沉积物隨洋壳板块向下俯冲。后又被仰冲到大陆板块下方,这导致大范围变形,产生逆冲断层和褶皱,引起高压-低温区域变质作用[1][5]

路堑显示方济会燧石岩石,格伦峡谷公园,旧金山,加利福尼亚。

参考文献 编辑

  1. ^ 1.0 1.1 Ernst, W. G. (1970). "Tectonic contact between the Franciscan Mélange and the Great Valley Sequence—Crustal expression of a Late Mesozoic Benioff Zone". Journal of Geophysical Research. 75 (5): 886–901. Bibcode:1970JGR....75..886E. doi:10.1029/JB075i005p00886. ISSN 2156-2202
  2. ^ James O. Berkland (2), Loren A. Ray (1972). "What is Franciscan?".AAPG Bulletin.56.doi:10.1306/819a421a-16c5-11d7-8645000102c1865d.ISSN 0149-1423
  3. ^ Wahrhaftig, Clyde (1984).A Streetcar to Subduction and Other Plate Tectonic Trips by Public Transport in San Francisco. Washington, D. C.: American Geophysical Union. doi:10.1029/sp022. ISBN 0875902340
  4. ^ HAMILTON, WARREN (1969). "Mesozoic California and the Underflow of Pacific Mantle".Geological Society of America Bulletin.80(12): 2409. Bibcode:1969GSAB...80.2409H. doi:10.1130/0016-7606(1969)80[2409:mcatuo]2.0.co;2. ISSN 0016-7606
  5. ^ Wakabayashi, John (1992-01-01). "Nappes, Tectonics of Oblique Plate Convergence, and Metamorphic Evolution Related to 140 Million Years of Continuous Subduction, Franciscan Complex, California". The Journal of Geology. 100 (1): 19–40. Bibcode:1992JG....100...19W. doi:10.1086/629569. ISSN 0022-1376. S2CID 140552742)