Andriyko Vitaly

Faculty geology

Specialization «Geological survey, search and secret service»

Structural and geodynamic conditions of formation and geochemical characteristics of basic and ultrabasic breeds of Azov in connection with the prediction of mineralization

Scientific adviser: professor Alekhin Victor

Summary on the final work

Contents

General description of work

     The Azov block of the Ukrainian crystalline shield in recent years found promising geological structures for new types of minerals. These structures are associated with arrays of basic and ultrabasic rocks. The work is relevant in connection with the fact that the structural–geodynamic position of these structures and their geochemical characteristics not well understood. This situation limits the ability to forecast new ore sites in the area of research.
     Work relates to the priority thematic areas of BIS «High–efficient equipment and energy saving technologies in mining, exploration and oil and gas industries» main research directions and important problems of basic research in the field of natural, technical sciences and humanities at the 2009–2013 year.
     Objective - set the structural–geodynamic conditions of formation and geochemical characteristics of basic and ultrabasic rocks of the Azov Sea, which is related to many occurrences (diamonds, Ni, Cu, etc.)
     Research Objectives:
     1. Synthesize data on the tectonic position, geological structure and material composition of basic and ultrabasic rocks of Azov.
     2. Establishing the geochemical features of rocks.
     3. Identification of major structural and geodynamic factors that contribute to the formation of promising ore–bearing structures.
     4. Development of recommendations for prediction of new ore–bearing objects in the Sea of Azov.
     Object of study are the basic and ultrabasic rocks Azov block of the Ukrainian crystalline shield and its suburbs.
     Subject of study – the chemical composition and the structural-geodynamic conditions of formation of arrays of basic and ultrabasic rocks.
     Research Methods – the structural–geological, geochemical, mathematical statistics methods, geophysical and tectonophysical.
     Novelty of the results – the first time evaluated the structural-geodynamic position of kimberlite bodies using geophysical method of structural–geodynamic mapping (SGDK–A) and tectonophysical methods, new data on the geochemical characteristics of rocks under study.
     Practical significance of the work – use the results in practice, geological surveying, prospecting and exploration in the Sea of Azov.
     Work approbation: The results of studies prepared by the article and the report of the international conference on the 90 th anniversary of Donetsk National Technical University, 80 th anniversary of the Geology Department and the 60 anniversary of the department of minerals and environmental geology (September 2011) The work will be submitted to the contest of research works of students in the 2011–2012 academic year.

State of the problem

     Origin of basic and ultrabasic rocks associated with the upper mantle. In ultramafic melts potential of oxygen is low, they contain hydrocarbon fluids. In these rocks are found H2 oxidized form of Ti (Ti3 +), C, which indicates that reducing conditions formation of ultramafic magma. In olivine from kimberlite was discovered by Cr2 + – indicator very reducing environment.
From typical igneous rocks of the Earth's crust – the granites and basalts, ultramafic differ sharply higher content of Mg, Cr and Ni, low-Si, low – Al, Na, K and Ti.
     Clarks concentration of elements in ultramafic (compared with Clark crust) revealed «series of mantle».
On the nature of the ultramafic mantle indicated by high concentrations of clarks (compared with Clark crust) elements such as Ni, Cr, Mg, Co, Fe, Mn. In picrites, kimberlites, pyroxenites, together with a large number of Mg and Fe content as much Ca. Some of them elevated content of alkali metals (Na or K) and other elements characteristic of alkaline rocks, – Li, B, C, Rb, Sr, P, Ti, Zr, Nb, Cs, Ba, Ta, Pb, U , Th. On ultrabasic rocks associated deposits of many minerals – chromite, platinum, titanomagnetite diamond [2].
     For basic rocks also have high concentrations of Ni, Cr, Co, Mg, Mn. Specific elements – Sc, Ca, V, Cu, Ti, Sb, F, P, Zn, Cd. LV Towson highlighted the main geochemical types of basalts. Much information has a value of the coefficient K, calculated on the amount of Ba + Sr to the amount of Ba + Sr. Extreme values of this coefficient differing 52 times:

Geochemical types of basalts on L.V. Towson

     By LS Borodin, with fractional differentiation of basic magmas despite the previously held views respected «the principle of coherence», ie, the dual change in the content of major and rare lithophile elements – Y, Zr, Nb, La, Ce, Ba, Rb, etc.
     Redox conditions for the formation of tholeiitic basalts are different. Most recovered, containing only Fe2 +, presumably directly related to the upper mantle. In these rocks found Eu2 + – analog earth elements, dramatically different from most other rare earths (TR3 +). Eu2 + – analog Sr2 +, which is explained by the proximity of Ri (0,125 and 0.121 nm). Yb also transformed into a divalent state and is analogous Mg. Less recovered basalts contain and fayalite (Fe2SiO4), and magnetite (Fe3O4). Finally, for the most oxidized species is characteristic only of magnetite. A good indicator is the ratio of alkaline basalts La3 + / Lu3 +.
     With the differentiation of basic magma associated formation of copper-nickel (Norilsk, Kola Peninsula), titanium–magnetite V (Urals) and other ore deposits (Distler VV, etc.)
     Ultrabasic and basic rocks belong to protokristallizatsii (by Fersman). For minerals protokristallizatsii characterized a variety of elements – an impurity, whose accumulation is largely explained by the laws of isomorphism. For example, in olivine concentrated Ni2 + and Mg2 +. Mn is more concentrated in iron olivines. In pyroxenes concentrated Ni, Co, Cr, Mn, Sc, V, etc., in the amphibole – Mn, Sc, Ni, Co, V, Zn, Cr, and sometimes other items.
     Basic and ultrabasic rocks Azov occupy different tectonic positions. For example, according to SG Krivdika and VI Tkachuk, in the October–built complex array (Proterozoic) are located on the periphery of the array. According Vasilchenko VV, Strekozov SN Borodyni BV, Latsko VG and others within the Azov revealed a lot of diabase and lamprophyre dikes of different ages, which are located along fault zones. Devonian ultramafic basites and often confined to the intersections of major fault zones. Near the junction between the Donbass Priazovya found four bodies kimberlites. These bodies are controlled by faults. On sections of some bodies identified Permian dikes trachytes, which indicates that the activity of these sites and in later periods.

Results of the structural-geodynamic studies

     Carried out reconnaissance work in the areas of individual bodies and arrays of basic and ultrabasic rocks. Planned detailed studies of the structural–geodynamic studies, including the ore–bearing areas (copper ore occurrences and kimberlites).
     Investigations were carried out near one of the kimberlite bodies. According to structural studies on the site are established numerous faults and dykes of various ages from Proterozoic to Permian. Results tectonophysical studies of Precambrian and Paleozoic rocks indicate a revolving tectonic activity. This is proved by different age stress fields that are installed on the site. A similar pattern was observed in the Devonian basalts close to. Vasilevka. Here basalts on Vasilevsky fault contact with Precambrian granitoids. Tectonophysical studies indicate geodynamic activity area in the Devonian and the Mesozoic. Here are found andesite dikes of Triassic age. Power Analysis of Neogene–Quaternary sediments indicates activity Basil fracture in Alpine orogeny era. On a site reconnaissance conducted research azimuthal electromagnetic method of structural–geodynamic mapping (SGDK–A) [9]. Profile is taken in the direction of Precambrian granitoid through Vasilevsky fault to Devonian basalts. Installed electrical conductivity of soil anomalies over the fault and beyond. Anomalies indicate the modern geodynamic activity of the site.

Geochemistry of basic and ultrabasic rocks of the Azov Sea

Table 1

Content and Clark concentration of chemical elements in ultramafic rocks of the Eastern Azov

(according to the semi-spectral analysis)

     The basic rocks of the Eastern Azov marked accumulation and shortage of the following elements (Table 2):

Table 2

Content and Clark concentration of chemical elements in basic rocks of the Eastern Azov

(according to the semi-spectral analysis)

     As seen from Table 2, the basic rocks of the Eastern Azov about clarke crust observed accumulation and shortage of the following elements.      Gabbro, accumulation: As20, 2006 - P5, 1957 - Yb5 - Mo2, 1945 - Ti2, 36 - W2, 1931 - Co1, 1946 - Zn1, 1942 - Mn1, 1918
     deficit: Ce0, 1928 - Be0, 1932 - Li0, 1932 - Sr0, 1941 - Ag0, 1942 - Ni0, 1948 - Y0, 59 - La0, 1962 - Pb0, 1966 - V0, 7 - Cr0, 7 - Ba0, 75 - Cu0, 1978 - Ga0, 1985 - Nb0, 9 - Sn0, 1992 - Zr0, 93;
     Diabase, accumulation: As20, 2006 - Yb8, 1933 - W4 - Mo3, 2009 - Sn2, 2004 - P2, 03 - Nb1, 1982 - Ti1, 1981 - Co1, 7 - Zn1, 1955 - Zr1, 1948 - V1, 36 - Pb1, 1927 - Cr1, 1926 - Cu1, 1912 - Ni1, 2005
     deficit: Be0, 1932 - Sr0, 1944 - Ce0, 1951 - Mn0, 1953 - La0, 1961 - Y0, 65 - Ag0, 1971 - Ga0, 1977 - Li0, 1993 - Ba0, 1998
     From these series can be seen that the ultramafic and basic rocks mostly accumulated arsenic (As), whose concentration is maximum and the average over Clark in more than 20 times. In kimberlites Novolaspinskogo area may be noted the accumulation of these elements: Li5, 43, Yb4, Nb2, 97, P2, 1953, Ba2, 24 .– in the tube «Hope»; accumulate Ni4, 0, Yb4, Cr3, 47, Co2, 72, Li2, 4. – A tube of «South». A large excess clarke noted for Yb5, W2, 69 in the tube «Novolaspinskaya. In the tube «Hope» Li concentration is much greater than in the «South». Deficit in kimberlites can be considered such elements: Y0, 34, Sr0, 44, Be0, 55 in the tube «Hope»; Be0, 26, Ag0, 42, Sr0, 44 in the tube, «South" and Ce0, 21, Li0, 22, Sr0, 35 in the tube «Novolaspinskaya».
     Among the ultramafic rocks of the Eastern Azov most celebrated The supply of these elements: Yb5, Co3, 48, Cr2, 1958, V2, 52, Cu2, 4, Ti2, 35, Ni2, 13 in the lamprophyres and Co5, 18, Yb4, 33, Cr4, V3 , 57, Cu3, 43, Ni3, 4, Ti3, 2, W3, 15 in the pyroxenites. Scarce in lamprophyres can be considered Ce0, 27, Li0, 36, Sr0, 43 and Li0, 19, Be0, 24, Ce0, 24 in the pyroxenites. If we compare these rocks with kimberlites Novolaspinskogo area, then here it is important to note an increased content of Co5, 18, and Cr4.
     In the basic rocks of the Eastern Azov accumulated elements: P5, 57, Yb5, Mo2, 45, Ti2, 36, W2, 31 – in the gabbro, Yb8, 1933, W4, Mo3, 09, Sn2, 04, P2, 03 – in the diabase . It is important to note that the accumulation of P in the gabbro is much more than the diabase, and W is less. Scarce in these rocks are Ce0, 28, Be0, 32, Li0, 32 – in the gabbro, Be0, 32, Sr0, 44, Ce0, 51 – in the diabase [13].
     According to the results the graphs for each species, reflecting the degree of accumulation or deficiency of the element relative to clarke crust. In the graphs Clark crust reflects the value of 1. For better visibility of schedules removed As.

Histogram clarke concentrations of elements in the rock (resolution 622x266, frame 7, the number of repetitions of 5)

Conclusions

     As is evident from the results of research arrays, and the body of basic and ultrabasic rocks are significantly different tectonic position, the host rocks and composition. Common is their confinement to discontinuous dislocations of different levels. In most cases, parts of these bodies have a long history of development and renewable geodynamic activity. Very diverse composition of the rocks. Even within the same group of rocks - kimberlites, which are localized in one area, there are significant differences. Especially for Ni and Cr. These differences can be explained by different local geodynamic conditions during the formation of bodies and the subsequent influence of young magmatic processes. Changes previchnogo of kimberlite is found in other kimberlites of the world - Africa, Yakutia, Arkhangelsk and other elevated concentrations Clark Ni and Cu in pyroxenites and gabbros are promising of these rocks in search of copper-nickel ores. In what will be a detailed analysis of specific arrays of these rocks Azov.

     At present master thesis is on the stage dorobotki and complement the theoretical material. After December 2011. Full text of the paper available from the author or supervisor.

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For the preparation of this work were used materials from the site http://masters.donntu.ru

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