Models of permeability contrasts in subduction zone melange: Implications for gradients in fluid fluxes, Syros and Tinos Islands, Greece

被引:52
作者
Ague, Jay J. [1 ]
机构
[1] Yale Univ, Dept Geol & Geophys, POB 208109, New Haven, CT 06520 USA
基金
美国国家科学基金会;
关键词
subduction; melange; fluid flow; modeling; Greece; Cyclades;
D O I
10.1016/j.chemgeo.2006.08.012
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Geological and geochemical evidence from previous studies suggest limited fluid flow through the interiors of many blocks of subducted oceanic crust within meta-ultramafic or metasedimentary melange matrix on the islands of Syros and Tinos, Cyclades, Greece. This finding is provocative because metamorphic devolatilization of igneous and sedimentary rocks during subduction should have liberated substantial volumes of fluid. In an effort to address this problem, two-dimensional numerical models incorporating permeability anisotropy and devolatilization are used to investigate spatial patterns of steady-state fluid flow through subduction zone melange under high-pressure/low-temperature (HP/LT) conditions. The modeling shows that as the permeability of the melange blocks decreases relative to the melange matrix, more flow is diverted around the blocks into the matrix. The ratio of the maximum flux (in matrix) relative to the minimum flux (in blocks) increases with the permeability contrast between the matrix and the less permeable blocks. Order-of-magnitude variations in permeability produce order-of-magnitude spatial variations in fluid fluxes between block interiors and surrounding matrix; flux variations of a factor of 10 or more can be present over very short length scales (as little as meter scale). The largest fluxes are produced in the matrix adjacent to block margins lying sub-parallel to regional foliation and flow direction. Fluid-rock reaction on block margins would be greatest in these areas, leading to asymmetrical distributions of reaction progress around blocks (illustrated herein by field mapping of a melange block on Syros). However, syn-metamorphic deformation can rotate blocks and strip off reaction zones at their margins, so it is likely that reaction zone asymmetries are commonly disrupted in nature. The inferred absence of strong fluid-rock reaction within melange blocks on Syros and Tinos could reflect low permeabilities in block interiors which acted to divert flow into melange matrix. Consequently, fluxes of subduction zone fluids through the melange matrix could have easily been very large, while low permeabilities shielded block interiors from the regional flow to varying degrees. (c) 2006 Elsevier B.V. All rights reserved.
引用
收藏
页码:217 / 227
页数:11
相关论文
共 66 条
[1]   Regional metamorphic dehydration and seismic hazard [J].
Ague, JJ ;
Park, J ;
Rye, DM .
GEOPHYSICAL RESEARCH LETTERS, 1998, 25 (22) :4221-4224
[2]   Simple models of CO2 release from metacarbonates with implications for interpretation of directions and magnitudes of fluid flow in the deep crust [J].
Ague, JJ ;
Rye, DM .
JOURNAL OF PETROLOGY, 1999, 40 (09) :1443-1462
[3]   Fluid infiltration and transport of major, minor, and trace elements during regional metamorphism of carbonate rocks, Wepawaug Schist, Connecticut, USA [J].
Ague, JJ .
AMERICAN JOURNAL OF SCIENCE, 2003, 303 (09) :753-816
[4]  
Ague JJ, 2000, GEOLOGY, V28, P1123, DOI 10.1130/0091-7613(2000)28<1123:ROCFCR>2.0.CO
[5]  
2
[6]   Simple models of coupled fluid infiltration and redox reactions in the crust [J].
Ague, JJ .
CONTRIBUTIONS TO MINERALOGY AND PETROLOGY, 1998, 132 (02) :180-197
[7]  
Altherr R., 1977, 7 COLL GEOL AEGEAN R, P347
[8]  
AVIGAD D, 1988, ALPINE EVOLUTION CYC
[9]   STABLE ISOTOPIC EVIDENCE FOR FLUID ROCK INTERACTIONS IN THE IVREA ZONE, ITALY [J].
BAKER, AJ .
JOURNAL OF PETROLOGY, 1990, 31 (01) :243-260
[10]   Modeling metamorphic fluid flow with reaction-compaction-permeability feedbacks [J].
Balashov, VN ;
Yardley, BWD .
AMERICAN JOURNAL OF SCIENCE, 1998, 298 (06) :441-470