Well logging responses of UHP metamorphic rocks from CCSD main hole in Sulu terrane, eastern central China

Abstract

The lithologies of the Chinese Continental Scientific Drilling main hole (CCSD-MH) are mainly comprised of orthogneiss, paragneiss, eclogite, amphibolite, and ultramafic rocks. The statistical results of logs of CCSD-MH indicate that ultramafic rocks are characterized by very high CNL (neutron log) and very low GR (gamma ray log) and RD (resistivity log); eclogites are characterized by high DEN (density), V _P (P-wave velocity) and PE (photoelectric absorption capture cross section); orthogneiss and paragneiss are characterized by high GR, U (uranium content), Th (thorium content), K (potassium content) and RD, and low DEN, PE, and CNL; logging values of amphibolite are between the logging values of eclogites and paragneiss. In addition, the logs could reflect the degree of retrograde metamorphism of eclogites. The upper section (100–2 000 m) shows higher DEN, PE, V _P, and lower GR, U, Th, K, RD than the lower section (2 000–5 000 m). Most logs of the upper section are more fluctuant than those of the lower section. This indicates that the upper section has more heterogeneities than the lower section. The cross plots of logs indicate that DEN, GR, K, and CNL are more powerful in identifying ultrahigh pressure metamorphic (UHPM) rocks at the CCSD-MH. GR value of the rocks from CCSD-MH shows obviously an increasing trend from ultramafic rock (the most mafic rocks at CCSD-MH) to orthogneiss (the most acid rocks at CCSD-MH). On the contrary, DEN value decreases from the ultramafic rock to the orthogneiss. CNL log is a good indicator of the content of structure water in crystalline rocks.

Keywords

ultrahigh pressure metamorphic rock / CCSD main hole / well logging response

References

[1] Ames L., Zhou G., Xiong B.. Geochronology and Isotopic Character of Ultrahigh-Pressure Metamorphism with Implications for Collision of the Sino-Korean and Yangtze Cratons, Central China. Tectonics, 1996, 15: 472-489.

[2] Brudy M., Zoback M. D.. Compressive and Tensile Failure of Boreholes Arbitrarily-Inclined to Principal Stress Axes: Application to the KTB Boreholes, Germany. International Journal of Rock Mechanics and Mining Science & Geomechanics Abstracts, 1993, 30(7): 1035-1038.

[3] Demezhko D. Y., Shchapov V. A.. 80 000 Years Ground Surface Temperature History Inferred from the Temperature-Depth Log Measured in the Superdeep Hole SG-4 (the Urals, Russia). Global and Planetary Change, 2001, 29(3–4): 219-230.

[4] ELEKTB Group KTB and the Electrical Conductivity of the Crust. Journal of Geophysical Research, 1997, 102(B8): 18289-18305.

[5] Fridleifsson G. O., Elders W. A.. The Iceland Deep Drilling Project: A Search for Deep Unconventional Geothermal Resources. Geothermics, 2005, 34(3): 269-285.

[6] Hacker B. R., Ratschbacher L., Webb L., . U/Pb Zircon Ages Constrain the Architecture of the Ultrahigh-Pressure Qinling-Dabie Orogen. Earth and Planetary Science Letters, 1998, 161: 215-230.

[7] Jin Z. M., Ou X. G., Kern H., . Elastic Wave Velocities of the 2 000 m Depth at Chinese Continental Scientific Drilling: Constraints on Deep Seismic Reflection. Acta Petrologica Sinica, 2004, 20(1): 80-96.

[8] Kern H., Jin Z. M., Gao S., . Physical Properties of Ultrahigh-Pressure Metamorphic Rocks from the Sulu Terrain, Eastern Central China: Implications for the Seismic Structure at the Donghai (CCSD) Drilling Site. Tectonophysics, 2002, 354(3–4): 315-330.

[9] Li X. P., Richwalski S.. Seismic Attenuation and Velocities of P- and S-Waves in the German KTB Area. Journal of Applied Geophysics, 1996, 36(2–3): 67-76.

[10] Liu F. L., Xu Z. Q., Xue H. M.. Tracing the Protolith, UHP Metamorphism, and Exhumation Ages of Orthogneiss from the SW Sulu Terrane (Eastern China): SHRIMP U-Pb Dating of Mineral Inclusion-Bearing Zircons. Lithos, 2004, 78(4): 411-429.

[11] Liu Q. S., Liu Q. S., Zhang Z., . Magnetic Properties of Ultrahigh-Pressure Eclogites Controlled by Retrograde Metamorphism: A Case Study from the ZK703 Drillhole in Donghai, Eastern China. Physics of the Earth and Planetary Interiors, 2007, 160(3-4): 181-191.

[12] Lund B., Zoback M. D.. Orientation and Magnitude of in situ Stress to 6. km Depth in the Baltic Shield. International Journal of Rock Mechanics and Mining Sciences, 1999, 36(2): 169-190.

[13] Manov D. V., Abercrombie R. E., Leary P. C.. Reliable and Economical High-Temperature Deep-Borehole Seismic Recording. Bulletin of the Seismological Society of America, 1996, 86(1A): 204-211.

[14] Niu Y. X., Pan H. P., Wang W. X., . Geophysical Well Logging in Main Hole (0–2 000 m) of Chinese Continental Scientific Drilling. Acta Petrologica Sinica, 2004, 20(1): 165-178.

[15] Okey A. I., Xu S. T., Sengor A. M. C.. Coesite from the Dabie Shan Eclogites, Central China. European Journal of Mineralogy, 1989, 1: 595-598.

[16] Ou X. G., Jin Z. M., Wang L., . Thermal Conductivity and Its Anisotropy of Rocks from the Depth of 100–2 000 m Mainhole of Chinese Continental Scientific Drilling: Revelations to the Study on Thermal Structure of Subduction Zone. Acta Petrologica Sinica, 2004, 20(1): 109-118.

[17] Papasikas N., Juhlin C.. Interpretation of Reflections from the Central Part of the Siljan Ring Impact Structure Based on Results from the Stenberg-1 Borehole. Tectonophysics, 1997, 269(3–4): 237-245.

[18] Pechnig R., Haverkamp S., Wohlenberg J., . Integrated Log Interpretation in the German Continental Deep Drilling Program: Lithology, Porosity, and Fracture Zone. Journal of Geophysical Research, 1997, 102(B8): 18363-18390.

[19] Popov Y. A., Pevzner S. L., Pimenov V. P., . New Geothermal Data from the Kola Superdeep Well SG-3. Tectonophysics, 1999, 306(3–4): 345-366.

[20] Rowley D. B., Xue F., Tucker R. D., . Ages of Ultrahigh-Pressure Metamorphism and Protolith Or thogneisses from the Eastern Dabieshan: U-Pb Zircon Geochronology. Earth and Planetary Science Letters, 1997, 151: 191-203.

[21] Schiffman P., Watters R. J., Thompson N., . Hyaloclastites and the Slope Stability of Hawaiian Volcanoes: Insights from the Hawaiian Scientific Drilling Project’s 3-km Drill Core. Journal of Volcanology and Geothermal Research, 2006, 151(1–3): 217-228.

[22] Wang R. C., Xu S. J., Xu S. T.. First Occurrence of Preiswerkite in the Dabie UHP Metamorphic Belt. Chinese Science Bulletin, 2000, 45: 748-750.

[23] Wang X. M., Liou J. G., Mao H. K.. Coesite-Bearing Eclogite from the Dabie Mountains, Central China. Geology, 1989, 17: 1085-1088.

[24] Xu H. J., Jin Z. M., Ou X. G., . Effects of Retrogression of Ultrahigh-Pressure Eclogites on Magnetic Susceptibility and Anisotropy. Earth Science-Journal of China University of Geosciences, 2004, 29(6): 675-685.

[25] Xu J., Chen Y. C., Wang D. H., . Titanium Mineralization in the Ultrahigh-Pressure Metamorphic Rocks from Chinese Continental Scientific Drilling 100-2 000 m Main Hole. Acta Petrologica Sinica, 2004, 20(1): 119-126.

[26] Xu S. T., Okay A. I., Ji S.. Diamond from Dabie Shan Metamorphic Rocks and Its Implication for Tectonic Setting. Science, 1992, 256: 80-82.

[27] Xu Z. Q.. The Scientific Goals and Investication Progresses of the Chinese Continental Scientific Drilling Project. Acta Petrologica Sinica, 2004, 20(1): 1-8.

[28] Yang J. S., Jin Z. M., Ou X. G., . Ultrahigh-Pressure Rock, Density, Buoyancy, Exhumation Mechanism, Exhumation Rate. Acta Petrologica Sinica, 2005, 21(2): 427-437.

[29] Yang W. C.. Understanding Seismic Reflectors in UHP Crust via CCSD-PP2 Hole. ICDP Newslett., 2000, 2: 22-23.

[30] You Z. D., Su S. G., Liang F. H., . Petrography and Metamorphic Deformation History of Ultrahigh-Pressure Metamorphic Rocks from the 100–2 000 m Core of Chinese Continental Scientific Drilling, China. Acta Petrologica Sinica, 2004, 20(1): 43-52.

[31] Zhang R. Y., Hirajima T., Banno S., . Petrology of Ultrahigh-Pressure Rocks from the Southern Su-Lu Region, Eastern China. Journal of Metamorphic Geology, 1995, 13: 659-675.

[32] Zhang Z. M., Shen K., Xiao Y. L., . Mineral and Fluid Inclusions in Zircon of UHP Metamorphic Rocks from the CCSD-Main Drill Hole: A Record of Metamorphism and Fluid Activity. Lithos, 2006, 92: 378-398.

[33] Zhang Z. M., Xu Z. Q., Xu H. F.. Petrology of Ultrahigh-Pressure Eclogites from the ZK703 Drillhole in the Donghai, Eastern China. Lithos, 2000, 52(1–4): 35-50.