| Title | Fluid infiltration, heat transport, and healing of microcracks in the damage zone of magmatic veins; numerical modeling |
| Author | Engvik, L.; Stöckhert, B.; Engvik, A.K. |
| Author Affil | Engvik, L., Sor-Trondelag University College, Department of Technology, Trondheim, Norway. Other: Ruhr-University Bochum, Federal Republic of Germany; Geological Survey of Norway, Norway |
| Source | Journal of Geophysical Research, 114(B5), Citation B05203. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0148-0227 |
| Publication Date | 2009 |
| Notes | In English. 32 refs. GeoRef Acc. No: 299425 |
| Index Terms | Antarctica--Queen Maud Land; alteration; Antarctica; cracks; Darcy's law; field studies; fluid dynamics; granites; heat flow; heat transfer; high-grade metamorphism; hydraulic fracturing; igneous rocks; infiltration; magmas; Mesoproterozoic; metamorphism; microcracks; numerical models; P-T conditions; pegmatite; plutonic rocks; Precambrian; Proterozoic; quantitative analysis; Queen Maud Land; upper Precambrian; veins |
| Abstract | Alteration halos with sharp boundaries are flanking pegmatitic veins in high-grade metamorphic and magmatic rocks of Dronning Maud Land, Antarctica. These halos are interpreted to represent the damage zone, formed as the wake of the process zone at the tip of the propagating magma-filled fracture and infiltrated by the fluid phase liberated from the crystallizing hydrous melt. On the basis of a set of assumptions, our numerical model explores the time scales of the infiltration processes, taking into account the combined effects of fluid flow, heat transfer, and temperature-dependent decay of interconnected porosity due to microcrack healing. Assuming an initial magma temperature of 700°C, a far field temperature in the host rock of 300°C, an initial porosity range of 0.5-2% in the damage zone, a permeability of 10-16 m2, and a pressure difference of 300 MPa, we find that the fluid infiltration into the damage zone proceeds within seconds to minutes and that the fluid flow contributes significantly to the heat transfer into the host rock. Assuming an initial microcrack aperture of 1 µm, the model predicts that the crack healing time scale is significantly longer than that of fluid infiltration in the case of thin veins with narrow damage zones; in this case, crack healing does not hinder fluid infiltration. Only for thick veins with high heat content and prolonged crystallization history does permeability become reduced by crack healing during progressive fluid infiltration. The results indicate that the formation of the alteration halos flanking pegmatitic veins may be a quasi-instantaneous process on geological time scales. |
| URL | http://hdl.handle.net/10.1029/2008JB005880 |
| Publication Type | journal article |
| Record ID | 88227 |