| CPC G01N 33/2028 (2019.01) [G01N 33/246 (2013.01)] | 2 Claims |
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1. A method for determining metallogenic potential of a porphyry by using trace elements and a B isotope of tourmaline, comprising:
S1, delineating a metallogenic section:
collecting geological data, geophysical data and geochemical data according to a selected research region, comprehensively analyzing a metallogenic prospect, and delineating a favorable metallogenic section;
S2, collecting samples:
collecting the samples from porphyries having metallogenic potential in the favorable metallogenic section, and picking out tourmaline in the samples;
S3, analyzing the tourmaline:
analyzing major elements of the tourmaline: observing features of the corresponding tourmaline under a microscope and a cathode luminescence image, recording petrographic features of the tourmaline in detail, analyzing contents of the major elements in the tourmaline in different regions by using an electron probe to obtain a molecular formula of the tourmaline, and determining a content of H2O in the tourmaline with the molecular formula of the tourmaline;
analyzing trace elements of the tourmaline: carrying out laser ablation inductively coupled plasma mass spectrometry in-situ micro-region element analysis on the tourmaline samples to obtain contents of the trace elements, comprising contents of Sr, Y and Cu elements, of the tourmaline of each test point; and
analyzing the B isotope of the tourmaline: carrying out multi-acceptance laser ablation inductively coupled plasma mass spectrometry in-situ B isotope analysis on the tourmaline samples to obtain δ11B isotope composition of each test point;
S4, determining metallogenic potential of the porphyry with oxygen fugacity, water content, and metal content and source:
wherein the oxygen fugacity is determined by: analyzing data obtained from analysis of the major elements, if a ratio of Fe3+/(Fe2++Fe3+) is less than 0.45 and a ratio of Mg/(Mg+Fe) is less than 0.5, it is indicated that the porphyries have no metallogenic potential of a porphyry, and otherwise, it is indicated that the porphyries containing the tourmaline have potential to form porphyry copper;
the water content is determined by: analyzing data obtained by analyzing the major element and analyzing the trace elements, if a content of H2O is less than 3.58 and a ratio of Sr/Y is less than 200, it is indicated that the porphyries have no metallogenic potential of a porphyry, and otherwise, it is indicated that the porphyries containing the tourmaline have the potential to form the porphyry copper;
the metal content is determined by: analyzing data obtained by analyzing the trace elements, if a content of Cu is less than 1.5 and a ratio of Sr/Y is less than 200, it is indicated that the porphyries have no metallogenic potential of a porphyry, and otherwise, it is indicated that the porphyries containing the tourmaline have a high content of Cu and have the potential to form the porphyry copper; and
the source is determined by: analyzing data obtained by analyzing the B isotope, if the tourmaline in the porphyries satisfies a content of δ11B being between −8.5 and −5 and a ratio of Sr/Y being lower than 200, it is indicated that the porphyries have a contribution of mantle-derived magma and have the potential to form a porphyry copper deposit;
if the porphyries is determined to have the high water content, oxygen fugacity and metal content of the magma according to above four determination conditions, the porphyries have a contribution of a mantle-derived material, and have excellent copper metallogenic potential, the porphyries are capable of being determined as a copper metallogenic rock mass, and a possibility of finding copper is greater than 80%, a prospecting target region is delineated within a certain radius according to an exposure position of the porphyry; and otherwise the porphyries are a non-metallogenic rock mass having small prospecting potential, and a target region is not delineated.
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