Tarhan method in the chemical properties and determinations of carbonatoblastites
Authors: Tarhan Niyazi 
Published: September 2024

Up to now, in geology/earth science literature, carbonatites (carbonatic rocks) have been accepted as magmatic-origin, rarely seen in nature, depth rocks (plutonic). As a result of our scientific studies (field, petrography, mineralogical etc.), it has been definitely determined that carbonatites are not magmatic-origin intrusion, carbonatic dyke, pegmatitic, stock and lens-type depth rocks. On the other hand, carbonatites develop in the regional dynamothermal Tarhan metamorphism cycle, in the second phase, under the changing physical conditions (P/T) of the Abukuma type reversed regional regressive dynamothermal metamorphism facies and sub-facies, where temperatures are effective compared to the developed pressures (T>P, temperatures have left their mark on metamorphism). The previously existing (pre-exiting) pure-impure primary source rock units, carbonate/limestones and primary source rock units develop within pure-impure marbles, which are metamorphic equivalents of Barrow type regional progressive dynamothermal metamorphism, where pressures are effective compared to temperatures in the first phase of the metamorphism cycle (P>T, pressures mark the metamorphism). They were derived from the rock units in question in solid phase and in-situ (autochthonous where they are). Therefore, carbonatites, which have been known as magmatic-originated depth rocks until today, are metamorphic-originated, rootless, metablastic rock series and derivatives, which are a type of new modern metamorphic rocks. It has been determined that they are carbonatoblastite type metablastic rocks with different primary rocks of origin (pure-impure carbonate/limestone). Up to now, carbonatites have been determined by a very expensive method according to O/C isotope ratios. However, carbonatites accepted to be of magmatic origin correspond to carbonatoblastites of metamorphic origin. Therefore, it has been suggested to apply the Tarhan Method, which is much cheaper and more practical in the determination of carbonatoblastites. According to the Tarhan method, petrographic thin sections are made from pure-impure carbonate/limestone, pure-impure limestones and pure-impure carbonatoblastites. In the polarized light microscope, optical signals/marking of single optical axis minerals (uniax minerals) of different carbonate type minerals in petrographic thin sections of different carbonate rocks are determined (quartz, calcite, calcite-dolomite, dolomite, apatite, nepheline, siderite, aragonite, witherite, stronsionite etc.). Single optical axis rock-forming main minerals of different carbonate origin and other rock-forming main single optical axis silicate minerals (quartz, orthoclase, foid, etc.) found together with the minerals in question often give a single optical axis optically positive (+) sign (ne > no). The petrographic thin section giving optically positive (+) sign shows that the rock sample belonging to it is carbonatoblastite (known as rare carbonatites of magmatic origin) type, 3rd generation metamorphic rock. If the main different carbonate minerals with rock-forming minerals and the main silicate minerals with single optical axis rock-forming minerals found together with them mostly give single optical axis optically negative (-) sign (ne < no), the mentioned petrographic thin sections indicate that they belong to limestone/carbonate which are 1st generation pure-impure primary source rocks of sedimentary origin and 2nd generation pure-impure marbles of metamorphic origin. However, the single optical negative (-) sign of different carbonate type minerals of marbles is much more effective than the optically negative (-) signs of different carbonate minerals that form limestones. As a result; Carbonatoblastic rock series and their derivatives/carbonatoblastites (known as carbonatites, which are rare depth rocks of magmatic origin) generally have a positive (+) sign (ne > no) with a single optical axis. In other words, all carbonate-based carbonatoblast and silicate-based rock-forming main-secondary-trace anhydrous, light-colored, expanding cage/structured, tectosilicate/framework crystalloblast neominerals are generally single-axis positive (+) sign. However, the carbonate-dominated rock-forming main carbonate minerals within the vertical and lateral gradual transition zones of carbonatoblastites and marbles (metamixitic metamorphic transition zone) have a single optical axis with optically negative-positive (±) and optically positive-negative (±) signs.