TY - JOUR

T1 - Deep structure and evolution of the Harz Mountains

T2 - results of three-dimensional gravity and finite-element modeling

AU - Gabriel, G.

AU - Jahr, T.

AU - Jentzsch, G.

AU - Melzer, J.

N1 - Funding Information: This work was supported by BEB Erdgas Erd~l GmbH, Hannover, and research funds of the government of Niedersachsen. Most of the field work was carried out by Geophysik GGD, Leipzig. D. H~inig, W. Conrad and H. J. Franzke are acknowledged lbr fruitlul discussions concerning geophysical and geological questions. S. Schmidt and H.-J. G6tze enable the use of the gravity modeling package IGAS and advised us in our work based on their experiences. The finite-element modeling was done at the Regional Computer Center of Lower Saxony with the software ABAQUS (1988), developed by Hibbitt, Karlsson and Sorensen, Inc. The authors thank H. Toms for a lot of helpful comments on the manuscript. We gratefully acknowledge valuable suggestions by C. Prodehl and two anonymous reviewers.

PY - 1997/3/15

Y1 - 1997/3/15

N2 - A new Bouguer anomaly map is presented for the region of the entire Harz Mountains based on more than 60,000 gravity values. The various gravity anomalies are discussed and interpretation is carried out by high-resolution 3-D gravity modeling. One of the main subjects of interest in the investigation is the northern boundary fault zone of the Harz Mountains, separating the Mesozoic sediments in the north from the Palaeozoic rocks of the Harz in the south. Dip and vertical displacement are determined for this fault zone: mean values are 3400 m and 70°, respectively. Gravity modeling shows that the Brocken and the Ramberg Granites are distinctly different. The Brocken Granite is shallow, whereas the Ramberg Granite has a maximum depth of 8.5 km and a N-S dimension of 37 km. The prominent Benneckenstein Gravity High is explained by two different models, one based on a granodioritic intrusion (2900 kg/m3) with a center-depth of 14 km and the other based on phyllites (2740 kg/m3) on a depth of 3-4 km. Studies on the geodynamic evolution of the Harz Mountains are carried out using the finite-element method. On the basis of a 3-D model, vertical displacements that can be related to horizontal forces are computed. For the period of the Variscan Orogeny an uplift of 600 m in the Harz area is calculated, for Late Cretaceous and Tertiary 400 m are determined. The total amount of 1000 m is about 1/3 of the vertical displacement of the northern boundary fault zone of the Harz Mountains shown by the gravity modeling. These results do not contradict geological ideas.

AB - A new Bouguer anomaly map is presented for the region of the entire Harz Mountains based on more than 60,000 gravity values. The various gravity anomalies are discussed and interpretation is carried out by high-resolution 3-D gravity modeling. One of the main subjects of interest in the investigation is the northern boundary fault zone of the Harz Mountains, separating the Mesozoic sediments in the north from the Palaeozoic rocks of the Harz in the south. Dip and vertical displacement are determined for this fault zone: mean values are 3400 m and 70°, respectively. Gravity modeling shows that the Brocken and the Ramberg Granites are distinctly different. The Brocken Granite is shallow, whereas the Ramberg Granite has a maximum depth of 8.5 km and a N-S dimension of 37 km. The prominent Benneckenstein Gravity High is explained by two different models, one based on a granodioritic intrusion (2900 kg/m3) with a center-depth of 14 km and the other based on phyllites (2740 kg/m3) on a depth of 3-4 km. Studies on the geodynamic evolution of the Harz Mountains are carried out using the finite-element method. On the basis of a 3-D model, vertical displacements that can be related to horizontal forces are computed. For the period of the Variscan Orogeny an uplift of 600 m in the Harz area is calculated, for Late Cretaceous and Tertiary 400 m are determined. The total amount of 1000 m is about 1/3 of the vertical displacement of the northern boundary fault zone of the Harz Mountains shown by the gravity modeling. These results do not contradict geological ideas.

KW - Bouguer map

KW - Finite-element method

KW - Geodynamics

KW - Gravit

KW - Harz Mountains

UR - http://www.scopus.com/inward/record.url?scp=0030882350&partnerID=8YFLogxK

U2 - 10.1016/S0040-1951(96)00176-X

DO - 10.1016/S0040-1951(96)00176-X

M3 - Article

AN - SCOPUS:0030882350

VL - 270

SP - 279

EP - 299

JO - TECTONOPHYSICS

JF - TECTONOPHYSICS

SN - 0040-1951

IS - 3-4

ER -