Application of Enhanced Local Wave Number Technique to the Total Field Magnetic Anomalies for Computing Model Parameters of Magnetized Geological Structures

Yıl 2018, Cilt: 61 Sayı: 2, 163 - 174, 10.04.2018

Yunus Levent Ekinci

https://doi.org/10.25288/tjb.414015

Cited By: 2

https://izlik.org/JA78BM53EP

Öz

In this study, enhanced local wave number (ELWN) technique is presented to compute some model parameters of isolated and magnetized geological structures such as horizontal position (exact origin), depth and source geometry using the total field magnetic anomalies (TMAs). The technique uses analytical signal amplitude (ASA) and first- and second-degree horizontal and vertical derivatives of observed TMAs, and then simply computes the model parameters without requiring a priori knowledge about the nature of the causative magnetized body.

Additionally, inclination and declination angles of both magnetization and ambient field have no effects on the results. In the ELWN technique source geometry, viz., structural index (contact/fault, dyke, horizontal cylinder and sphere) is determined using the depth and exact origin computed previously. Hypothetic simulations performed using TMAs due to some simple shaped geological models have showed the ability of the technique. Moreover, an actual magnetic data taken over the Kesikköprü iron deposit (Central Turkey), one of the largest iron reserve in Turkey,has been also analysed. A depth of 21.39 m has been computed for the magnetized geological source which includes the mafic rocks rich in magnetic properties, and the iron ore body. The structural indices obtained have indicated a dike-like or an intermediate form between a dike and a horizontal cylinder body for the magnetized source. These findings are compatible with those of a recently published study.  Hence, the use of ELWN technique is proposed for rapid and reliable model parameter estimations from TMAs as an alternative or supportive experiment to the inverse modelling studies.

Anahtar Kelimeler

Directional derivatives , Enhanced local wave number , Magnetized geological structures , Model parameters , Total field magnetic anomalies

Manyetize Olmuş Jeolojik Yapıların Model Parametrelerinin Belirlenebilmesi için Gelişmiş Lokal Dalga Sayısı Tekniğinin Toplam Alan Manyetik Anomalilere Uygulanması

https://izlik.org/JA78BM53EP

Öz

Bu çalışmada, toplam alan manyetik anomaliler (TMA) kullanarak izole ve manyetize olmuş jeolojik yapıların ölçüm profili düzlemindeki yatay uzaklığı, derinliği ve yapı geometrisi gibi model parametrelerinin hesaplanabilmesi için gelişmiş lokal dalga sayısı (GLDS) tekniği sunulmuştur. Teknik, ölçülen TMA’lerin analitik sinyal genliğini (ASG) ve birinci- ve ikinci-dereceden yatay ve düşey türevlerini kullanmakta ve ardından manyetik anomaliye neden olan kaynağın doğası hakkında herhangi bir ön bir bilgiye ihtiyaç duymaksızın model parametrelerini kolay bir şekilde hesaplamaktadır. Ayrıca, mıknatıslanma ve ortam manyetik alan doğrultularının (eğim ve sapma açıları) sonuçlar üzerinde bir etkisi bulunmamaktadır. GLDS tekniğinde yapı geometrisi, yani yapısal indeksi (kontak/fay, dayk, yatay silindir ve küre) bir önceki hesaplamalardan elde edilen yapı derinliği ve yapının profil düzlemindeki yatay uzaklığı yardımıyla hesaplanmaktadır. Bazı basit şekilli jeolojik modellerden üretilen TMA’lerle gerçekleştirilen teorik uygulamalar tekniğin kullanışlılığını göstermiştir. Ayrıca, gerçek veri uygulaması olarak Türkiye’nin en büyük demir rezervlerinden biri olan Kesikköprü-Bala demir yatağında (Orta Türkiye) ölçülmüş TMA analiz edilmiştir.  Manyetik özellikçe zengin mafik kayaçları ve demir cevherini içeren manyetize olmuş kaynak yapı derinliği 21.39 m olarak hesaplanmıştır. Yapısal indeks değerleri ise dayk-benzeri veya dayk ve yatay silindir arası manyetize olmuş bir yapıyı işaret etmiştir. Bu bulgular yeni yayınlanmış bir çalışmanın sonuçlarıyla da uyumludur.  Bu nedenle, TMA’lerden hızlı ve güvenilir model parametreleri kestirimi yapabilmek için GLDS tekniğinin kullanımı ters çözüm çalışmalarına bir alternatif veya destekleyici çalışma olarak önerilmektedir.

Anahtar Kelimeler

Gelişmiş lokal dalga sayısı , Manyetize olmuş jeolojik yapılar , Model parametreleri , Toplam alan manyetik anomaliler , Yönsel türevler

Kaynakça

• Agarval, B.N.P. and Srivastava, S., 2008. FORTRAN codes to implement enhanced local wave number technique to determine the depth and location and shape of the causative source using magnetic anomalies. Computers and Geosciences, 34, 1843–1849.
• Balkaya, Ç., Göktürkler, G., Erhan, Z. and Ekinci, Y.L., 2012. Exploration for a cave by magnetic and electrical resistivity surveys: Ayvacık sinkhole example, Bozdağ İzmir (Western Turkey). Geophysics, 77 (3), B135-B146.
• Bingöl, E., 1989. Geological map of Turkey, scale: 1/2.000.000 (MTA (General Directorate of Mineral Research and Exploration of Turkey) Publications). Biswas, A., 2017. Inversion of source parameters from magnetic anomalies for mineral/ore deposits exploration using global optimization technique and analysis of uncertainty. Natural Resources Research, 27, 77–107.
• Boztuğ, D., 1998. Post-collisional central Anatolian alkaline plutonism, Turkey. Turkish Journal of Earth Sciences, 7, 145–165.
• Büyüksaraç, A., Yalçıner, C.Ç., Ekinci, Y.L., Demirci, A. and Yücel, M.A., 2014. Geophysical investigations at Agadere Cemetery, Gallipoli Peninsular, NW Turkey. Australian Journal of Forensic Sciences, 46 (1), 111–123.
• Cooper, G.R.J. and Cowan, D.R., 2006. Enhancing potential field data using filters based on the local phase. Computers and Geosciences, 32, 1585–1591.
• Doğan, B., Ünlü, T. and Sayılı, İ.S., 1998. An approach to the origin of Kesikköprü (Bala-Ankara) iron deposit. Bulletin of the Mineral Research and Exploration, 120, 1–35.
• Drahor, M.G., Kurtulmuş, Ö., Tuna, N., Berge, M.A., Hartmann, M. and Speidel, M.A., 2008. Magnetic imaging and electrical resistivity tomography studies in a Roman military installation found in Satala archaeological site, northeastern Anatolia, Turkey. Journal of Archaeological Sciences, 35, 259–271.
• Ekinci, Y.L. and Yiğitbaş, E., 2012. A geophysical approach to the igneous rocks in the Biga Peninsula (NW Turkey) based on airborne magnetic anomalies: geological implications. Geodinamica Acta, 25 (3–4), 267–285.
• Ekinci, Y.L., Ertekin, C. and Yiğitbaş, E., 2013. On the effectiveness of directional derivative based filters on gravity anomalies for source edge approximation: synthetic simulations and a case study from the Aegean Graben System (Western Anatolia, Turkey). Journal of Geophysics and Engineering, 10 (3), 035005.
• Ekinci, Y.L., Balkaya, Ç., Şeren, A., Kaya, M.A. and Lightfoot, C.S., 2014. Geomagnetic and geoelectrical prospection for buried archaeological remains on the Upper City of Amorium, a Byzantine city in midwestern Turkey. Journal of Geophysics and Engineering, 11 (1), 015012.
• Ekinci, Y.L., 2016. MATLAB-based algorithm to estimate depths of isolated thin dike-like sources using higher-order horizontal derivatives of magnetic anomalies. SpringerPlus, 5, 1384.
• Ekinci, Y.L., Özyalın, Ş., Sındırgı, P., Balkaya, G. and Göktürkler, G., 2017. Amplitude inversion of 2D analytic signal of magnetic anomalies through Differential Evolution Algorithm. Journal of Geophysics and Engineering, 14, 1492–1508.
• Hanna, W.F., 1990. Some historical notes on early magnetic surveying in the U.S. Geological Survey. In Hanna, W.F., (ed.), Geologic Applications of Modern Aeromagnetic Surveys. United States Geological Survey Bulletin, 1924, 63–73.
• Hinze, W.J., Von Frese, R.R.B. and Saad, A.H., 2013. Gravity and magnetic exploration: principles, practices, and applications. New York, Cambridge University Press.
• Kearey, P., Brooks, M. and Hill, I., 2002. An introduction to geophysical exploration. Oxford, Blackwell.
• Kuşcu, İ. and Erler, A., 1998. Mineralization events in a collision-related setting: the Central Anatolian Crystalline Complex, Turkey. International Geology Review, 40, 532–565.
• Mandal, A., Biswas, A., Mittal, S., Mohanty, W. K., Sharma, S. P., Sengupta, D., Sen J. and Bhatt, A.K., 2013. Geophysical anomalies associated with uranium mineralization from Beldih mine, South Purulia Shear Zone, India. Journal of the Geological Society of India, 82 (6), 601–606.
• Mandal, A., Mohanty, W.K., Sharma, S.P., Biswas, A., Sen, J. and Bhatt, A.K., 2015. Geophysical signatures of uranium mineralization and its subsurface validation at Beldih, Purulia District, West Bengal, India: A case study. Geophysical Prospecting, 63, 713–724.
• Nabighian, M.N., 1972. The analytic signal of twodimensional magnetic bodies with polygonal cross-section: its properties and use for automated anomaly interpretation. Geophysics, 37, 507–517.
• Oruç, B., 2013. Determination of horizontal locations and depths of magnetic sources using continuous wavelet transform. Yerbilimleri, 34, 177–190.
• Oruç, B. and Keskinsezer, A., 2008. Detection of causative bodies by normalized full gradient of aeromagnetic anomalies from east Marmara region, NW Turkey. Journal of Applied Geophysics, 65, 39-49.
• Oruç, B. and Selim, H., 2011. Interpretation of magnetic data in the Sinop area of Mid Black Sea, Turkey, using tilt derivative, Euler deconvolution, and discrete wavelet transform. Journal of Applied Geophysics, 74, 194–204.
• Pilkington, M., 2007. Aeromagnetic surveying, in Encyclopedia of Geomagnetism and Paleomagnetism, In Gubbins, D., and HerreroBervera E., (ed.), Springer, Dordrecht, pp. 1–3.
• Prakasa Rao, T.K.S., Subrahmanyan, M. and Srikrishna Murthy, A., 1986. Nomograms for direct interpretation of magnetic anomalies due to long horizontal cylinders. Geophysics, 51, 2156–2159.
• Reid, A.B., Allsop, J.M., Granser, H., Millett, A.J. and Somerton, I.W., 1990. Magnetic interpretation in three dimensions using Euler deconvolution. Geophysics, 55, 80–91.
• Salem, A., Ravat, D., Smith, S. and Ushijima, K., 2005. Interpretation of magnetic data using an enhanced local wave number (ELW) method. Geophysics, 70, L7–L12.
• Smith, R.S., Thurston, J.B., Dai, T. and MacLeod, I.N., 1998. iSPI—The improved source parameter imaging method. Geophysical Prospecting, 46, 141–151.
• Srivastava, S. and Agarval, B.N.P., 2010. Inversion of the amplitude of the two-dimensional analytic signal of the magnetic anomaly by the particle swarm optimization technique. Geophysical Journal International, 182, 652–662.
• Tatar, S. and Boztuğ, D., 1998. Fractional crystallization and magma mingling/mixing processes in the monzonitic association in the SW part of the composite Yozgat batholith (Şefaatli–Yerköy, SW Yozgat). Turkish Journal of Earth Sciences, 7, 215-230.
• Terzi, M.H. and Yılmazer, E., 2015. Geology and alteration mineralogy of Kesikköprü (BalaAnkara) iron-oxide deposit. The World Multidisciplinary Earth Sciences Symposium, 7-11 September, Prague (Czech Republic), pp. 243.
• Thompson, D.T., 1982. EULDPH: a new technique for making computer assisted depth estimates from magnetic data. Geophysics, 47, 31–37.
• Thurston, J.B., and Smith, R.S., 1997. Automatic conversion of magnetic data to depth, dip, and susceptibility contrast using the SPI method. Geophysics, 62, 807–813.