Geochemical features of hydrothermal rocks of the Murun alkaline complex

 Sychev V.Yu., Vladykin N.V.

 

 The Murun massif is one of few alkaline massifs showing the potassium agpaitic.

It is located in the north-west part of the Aldan shield. The massif is located close to the crossing of two large Precambrian faults. The massif is dated as 120-150 Ma and covers an area of 150 sq. km. It is related to the Mesozoic rifting of the Aldan shield.  It is composed of a wide spectrum of layered potassium alkaline rocks (from ultra-basic to granites). The latest differentiates of the massif include silicate-carbonate complex of charoite-carbonatite rocks (Vladykin 2000-2009). After the rocks of the massif had been crystallized the tectonic activity didn’t decrease and the massif is cut by numerous faults of different direction. These faults were saturated by hydrothermal solutions, coming from the deep-seated parts of the magmatic chamber. The host magmatic rocks underwent silicification and sulfitization. Those hydrothermal solutions are related to U, Au, Ag, Mo, Cu, Zn, Pb, Nb and Ti deposits and occurrences. The rocks being contrast in terms of the composition to the solutions are chemical barriers and a great number of elements which the solution bring, are crystallized here. Thus, anomalous concentrations of the following elements (in ppm) are found when they interact with the magnesia lamproites:  Pb- 3200, Sn- 90, Zn- 200, W более 100, Be- 60, Tl- 50,

Nb-3000, V- 2000, Cu- 400, Mo- 300, Ag-23, Au 0,6. When we studied fluid inclusions in quartz we found that the temperature of crystallization of fluid-solutions is  520o.