Evolution of gabbroic rocks of the Northern Apennine ophiolites (Italy): Comparison with the lower oceanic crust from modern slow-spreading ridges
Evolution of gabbroic rocks of the Northern Apennine ophiolites (Italy): Comparison with the lower oceanic crust from modern slow-spreading ridges
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DOI：
10.1130/0-8137-2349-3.129
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发表时间：
2000
影响因子：
2.5
通讯作者：
R. Tribuzio;M. Tiepolo;R. Vannucci
中科院分区：
文献类型：
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作者：
R. Tribuzio;M. Tiepolo;R. Vannucci
野外和岩相学关系以及主要和微量元素矿物化学使我们能够确定北方亚平宁蛇绿岩辉长岩的火成岩到高温变质演化。在低压条件下，正常洋中脊（N-MORB）类型的液体侵入非均匀地幔剖面形成的辉长岩。这些液体经历了由分离结晶控制的火成岩分异过程，最有可能与含挥发分的火成岩剂（可能是奥长花岗岩型液体）在辉长岩堆晶中的后期渗流有关。这样的岩浆分异过程产生了高度演化的液体，产生了富铁岩石（主要是含铁钛氧化物的闪长岩）。辉长岩在没有海水流体的韧性剪切带中经历了高温（T900 °C）重结晶。北方亚平宁蛇绿岩的辉长岩与现代缓慢扩张的山脊上发现的辉长岩有着惊人的相似之处，如西南印度洋海岭、大西洋中海岭（在其与凯恩断裂带的交汇处，即，MARK地区）和中开曼隆起。北方亚平宁蛇绿岩被解释为代表一个岩浆贫乏的缓慢扩张的中心，作为大陆岩石圈伸展的结果形成的化石类似物。
Field and petrographic relationships together with major and trace element mineral chemistry have allowed us to determine the igneous to high-temperature metamorphic evolution of the gabbroic rocks of the Northern Apennine ophiolites. Gabbroic rocks formed by the intrusion of liquids of normal mid-oceanic-ridge (N-MORB) type in a heterogeneous mantle section under low-pressure conditions. These liquids underwent an igneous-differentiation process controlled by fractional crystallization, most likely associated with late percolation in the gabbroic cumulate pile of a volatile-bearing igneous agent, possibly a trondhjemite-type liquid. Such an igneous-differentiation process produced highly evolved liquids that gave rise to Fe-rich rocks (mostly Fe-Ti oxide-bearing diorites). The gabbroic rocks underwent high-temperature (T 900 °C) recrystallization in ductile shear zones in the absence of seawater-derived fluids. The gabbroic rocks of the Northern Apennine ophiolites bear striking similarities to those recovered from modern slow-spreading ridges, such as the Southwest Indian Ridge, the Mid-Atlantic Ridge (at its intersection with the Kane Fracture Zone, i.e., the MARK area), and the Mid-Cayman Rise. The Northern Apennine ophiolites are interpreted to represent a fossil analogue of a magma-poor slow-spreading center that formed as a result of continental lithospheric extension.