METHOD FOR DETERMINING DIRECTION AND DISTANCE OF METALLOGENIC PLUTON OF SKARN DEPOSIT WITH GARNET

Abstract

A method for determining a direction and a distance of a metallogenic pluton of a skarn deposit with a garnet includes: collecting a sample; performing petrographic observation on the sample and designing an experimental area; computing a parameter; building a model; setting a parameter range; optimizing the parameters of the three models through a grid search method, and determining an optimal model and corresponding parameters a, b and c through repeated circulative iteration and by taking a minimum R as a limit condition; and substituting data of all sampling points into the optimal model, computing D of each sampling point, drawing a circle with a corresponding sampling point as a center and D as the radius, determining an intersection point of all circles as coordinates of the metallogenic pluton, and performing delineation with R as a buffer area of the metallogenic pluton.

Claims

1. A method for determining a direction and a distance of a metallogenic pluton of a skarn deposit with a garnet, comprising: (1) collecting a sample: collecting a representative garnet sample from the skarn; (2) performing petrographic observation on the sample and designing an experimental area: grinding a collected sample into a probe piece, and determining and marking a single mineral crystal area of the garnet; (3) computing a parameter: obtaining a trace element content of a marked area through laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) in-situ microanalysis, and computing a ratio (L/H) of a light rare earth content to a heavy rare earth content; (4) building a model: substituting the obtained ratio (L/H) of the light rare earth content to the heavy rare earth content into exponential models D=a(L/H){circumflex over ()}b and D=a(L/H){circumflex over ()}b+c and a logarithmic model D=a(ln(L/H)+4){circumflex over ()}(b+0.1); (5) setting a parameter range: setting a parameter a?[?1000,1000] with a step size of 50, and setting a parameter b?[?10,10] with a step size of 0.5 in the exponential model D=a(L/H){circumflex over ()}b; setting a parameter a?[?1000,1000] with a step size of 50, setting a parameter b ?[?10,10] with a step size of 0.5, and setting a parameter c?[?1000,1000] with a step size of 50 in the exponential model D=a(L/H){circumflex over ()}b+c; and setting a parameter a?[?1000,1000] with a step size of 50, and setting a parameter b?[?10,10] with a step size of 0.5 in the logarithmic model D=a(ln(L/H)+4){circumflex over ()}(b+0.1); (6) optimizing parameters of the model: optimizing the parameters of the three models through a grid search method, and determining optimized parameters a, b and c of the three models respectively through repeated circulative iteration and by taking a minimum R as a limit condition; wherein R represents an optimized buffer radius: $R=\frac{\underset{n}{\overset{i=1}{.Math.}}{D}^{}}{n}=\frac{\underset{n}{\overset{i=1}{.Math.}}.Math.\left(D_i-r_i\right).Math.}{n},$ and has a threshold?60 m; and n represents the samples number, i represents a sampling point i, D.sub.i represents a linear distance in m between an optimal location of the metallogenic pluton and the sampling point i, r.sub.i represents a linear distance in m between a location of the metallogenic pluton obtained from an optimal parameter model for the sampling point i and the sampling point i, and D represents an absolute value in m of a difference between D.sub.i and r.sub.i; and (7) locating and delineating the metallogenic pluton: taking a model with a minimum R among the three models as an optimal model, substituting data of all sampling points into the optimal model, computing D of each sampling point, drawing a circle with a corresponding sampling point as a center and D as the radius, determining an intersection point of all circles as coordinates (X, Y) of the metallogenic pluton, and performing delineation with R as a buffer area of the metallogenic pluton.

2. The method according to claim 1, wherein there are no less than 5 samples in step 1, and sample information comprises global positioning system (GPS) coordinate data, a field photo, lithology, alteration and a mineralization feature.

3. The method according to claim 1, wherein in step 2, an obtained probe piece is observed under a microscope, and a single mineral crystal of the garnet with a large particle size and a desirable crystal form is selected as the representative sample, and a rectangular area slightly larger than the particle size of the single mineral crystal is designed as an experimental test location and marked.

4. The method according to claim 1, wherein step 3 comprises creating a data table of a sum of a light rear earth and a heavy rare earth and the ratio (L/H) of the light rare earth content to the heavy rare earth content.

5. The method according to claim 1, wherein step 4 of building the model comprises: collecting the representative garnet sample from the skarn with coordinates of a metallogenic pluton known in advance; grinding the collected sample into the probe piece, and determining and marking the single mineral crystal area of the garnet; obtaining the trace element content of the marked area through LA-ICPMS in-situ microanalysis, computing the ratio (L/H) of the light rare earth content to the heavy rare earth content, and computing a distance D in meter between a sampling point and the coordinates of the metallogenic pluton; and obtaining the exponential models D=a(L/H){circumflex over ()}b and D=a(L/H){circumflex over ()}b+c by substituting the ratio (L/H) of the light rare earth content to the heavy rare earth content and the distance D into a linear model y=bx+a, and obtaining the logarithmic model D=a(ln(L/H)+4){circumflex over ()}(b+0.1) by substituting the ratio (L/H) of the light rare earth content to the heavy rare earth content and the distance D into a logarithmic model y=bln(x)+a.

6. The method according to claim 1, wherein after step 6 of optimizing the model parameters, if the R is still greater than 60 m, ranges of parameters a, b and c are redefined according to the parameters a, b and c returned after iteration and the step size is reduced until R returned is less than 60 m.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 shows thin-section photographs and microphotographs of garnet in Longgen skarn deposit, Tibet;

[0042] FIG. 2 shows a location model for a garnet and a metallogenic pluton of a skarn deposit in Longgen skarn deposit, Tibet; and

[0043] FIG. 3 shows model default parameter results (a-c) and parameter tuning optimization results (d-f).

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] A technical solution of the present disclosure will be further explained below through embodiments, which do not limit the protection scope of the present disclosure.

[0045] A specific implementation mode provides a method for determining a direction and a distance of a metallogenic pluton of a skarn deposit with a garnet. The method includes: [0046] (1) A representative garnet sample is collected from a skarn with coordinates of a metallogenic pluton known in advance. Longgen skarn lead-zinc deposit in Tibet is specifically selected, and at least 5 samples of garnet-bearing skarn are collected. Sampling information is recorded in Table 1.

TABLE-US-00001 TABLE 1 Information of Garnet Sample Sample Sampling No. position X Y Lithology Occurrence Mineral Photo LGGS06 136 52 Garnet-bearing skarn Massive Garnet ZP03 LGSK-1 TC301 411 365 Garnet-bearing skarn Massive Garnet ZP04 LGSK-5 TC501 283 223 Garnet-bearing skarn Vein Garnet ZP07 . . . . . . . . . . . . . . . [0047] (2) The collected sample is ground into a thin section, a single mineral crystal area of the garnet is determined and marked, a feature of the garnet is observed under a microscope, a single mineral crystal with a large particle size and a desirable crystal form is selected as the representative sample, and a rectangular area slightly larger than the particle size of the single mineral crystal is designed as an experimental test location and marked by using a marking pen, as shown in FIG. 1. [0048] (3) Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) in-situ microanalysis is performed on a selected experimental test location, a ratio (L/H) of a light rare earth content to a heavy rare earth content is computed, and a distance D in meter between a sampling point and coordinates of the metallogenic pluton is computed, with information shown in Table 2.

TABLE-US-00002 TABLE 2 Computation Results No La Ce Pr Nd Sm Eu Gd Tb Dy Ho 1 1.54 1.01 0.37 2.76 4.02 0.81 14.50 7.04 74.66 26.17 2 1.31 0.69 0.47 8.82 16.74 2.80 49.56 10.97 73.61 16.85 3 6.09 12.97 2.31 19.89 16.06 2.82 44.63 8.56 58.58 14.41 4 1.47 0.71 0.17 2.71 4.86 1.34 26.94 7.60 56.80 15.56 5 1.19 3.07 0.54 5.51 9.12 2.51 30.22 6.91 44.70 10.63 6 71.23 176.04 28.08 148.00 40.39 4.72 55.60 9.75 49.35 9.91 7 0.92 1.67 0.64 9.29 6.56 2.13 10.17 1.37 6.87 1.40 8 6.85 14.86 2.55 18.49 8.70 1.34 11.37 1.49 7.77 1.55 9 0.77 1.25 0.64 9.10 6.04 1.45 7.16 0.79 3.53 0.68 10 0.89 1.91 0.86 12.76 9.34 1.15 14.32 2.05 10.20 1.79 11 1.42 2.02 0.81 8.65 3.34 0.86 3.53 0.43 1.50 0.33 12 0.53 2.31 1.23 10.79 3.17 0.75 2.99 0.43 1.61 0.31 13 1.00 5.03 1.72 13.03 3.39 0.62 1.93 0.17 0.97 0.17 14 0.26 1.48 0.59 8.15 6.15 1.32 9.08 1.22 5.57 0.93 15 0.53 2.44 0.70 4.39 0.87 0.63 0.87 0.09 0.16 0.05 16 0.22 0.20 0.03 1.06 2.91 1.32 12.49 2.61 17.42 3.68 17 20.82 50.92 6.76 28.07 7.76 1.27 12.19 1.96 9.27 1.73 18 0.24 0.23 0.08 1.63 2.30 1.43 11.60 2.21 12.83 2.72 19 10.63 20.28 2.26 6.21 0.27 0.39 0.27 0.01 0.00 0.01 20 1.61 6.14 1.76 14.14 6.86 1.41 10.65 1.42 7.60 1.26 21 0.30 2.42 0.71 5.86 0.76 0.75 1.24 0.12 0.46 0.06 22 0.37 2.14 0.50 2.04 0.05 0.40 0.14 0.00 0.00 0.00 23 0.60 2.10 0.46 3.87 3.10 1.69 5.09 0.58 2.83 0.56 24 0.25 0.40 0.24 2.66 2.34 1.50 1.73 0.24 0.77 0.14 25 0.92 1.85 0.40 3.70 3.31 2.08 9.65 1.63 11.33 2.64 26 0.75 0.46 0.10 1.29 1.95 1.54 4.63 1.12 7.45 1.71 27 0.95 1.24 0.22 1.72 1.97 1.72 7.35 1.80 11.75 2.74 28 1.15 2.94 1.25 12.15 3.50 0.57 2.97 0.34 1.00 0.17 29 10.08 27.87 3.45 11.46 0.80 0.76 0.50 0.02 0.09 0.05 30 11.45 20.41 1.80 4.69 0.16 0.08 0.11 0.07 0.30 0.03 31 13.48 30.21 3.34 7.98 0.89 0.72 0.47 0.02 0.06 0.05 32 9.81 21.76 2.19 6.11 0.31 0.13 0.26 0.05 0.00 0.03 33 8.97 31.38 5.16 19.78 1.84 0.32 0.69 0.11 0.27 0.02 34 8.25 0.00 1.10 2.98 0.42 0.05 0.11 0.01 0.15 0.02 35 3.51 4.85 0.52 1.63 0.10 0.01 0.05 0.01 0.06 0.01 36 4.77 6.55 0.58 1.52 0.31 0.01 0.26 0.02 0.03 0.01 37 1.51 0.97 0.05 0.00 0.20 0.04 0.10 0.00 0.03 0.01 38 2.10 1.58 0.06 0.16 0.00 0.03 0.16 0.00 0.06 0.00 39 1.97 1.26 0.06 0.05 0.00 0.03 0.05 0.00 0.00 0.01 No Er Tm Yb Lu REE LREE HREE L/H D 1 85.44 12.07 71.32 7.03 308.72 10.51 298.22 0.04 1 2 43.55 5.60 26.90 3.63 261.51 30.83 230.68 0.13 3 3 40.03 4.81 30.97 4.52 266.65 60.15 206.51 0.29 19 4 46.65 5.80 35.86 4.40 210.87 11.26 199.61 0.06 2 5 30.14 3.72 22.53 3.04 173.84 21.94 151.90 0.14 6 6 23.71 2.10 11.02 1.42 631.32 468.47 162.85 2.88 44 7 3.71 0.36 2.09 0.20 47.37 21.21 26.16 0.81 14 8 2.87 0.39 1.83 0.26 80.33 52.79 27.54 1.92 49 9 1.30 0.18 0.82 0.13 33.84 19.25 14.59 1.32 48 10 3.81 0.55 1.66 0.28 61.57 26.92 34.66 0.78 20 11 0.86 0.19 0.47 0.19 24.61 17.11 7.50 2.28 41 12 0.69 0.05 0.48 0.20 25.54 18.78 6.76 2.78 41 13 0.34 0.01 0.63 0.09 29.10 24.79 4.31 5.76 50 14 2.15 0.13 1.21 0.26 38.48 17.94 20.54 0.87 15 15 0.16 0.04 0.24 0.03 11.19 9.56 1.63 5.87 49 16 8.13 0.98 6.81 1.14 59.00 5.73 53.26 0.11 3 17 3.70 0.46 2.40 0.35 147.66 115.60 32.05 3.61 43 18 6.37 0.77 5.54 0.94 48.89 5.90 42.99 0.14 4 19 0.04 0.00 0.06 0.00 40.44 40.04 0.39 101.68 195 20 2.38 0.26 2.12 0.35 57.95 31.91 26.04 1.23 50 21 0.07 0.01 0.09 0.00 12.84 10.79 2.05 5.27 43 22 0.00 0.00 0.00 0.00 5.63 5.49 0.14 40.58 157 23 0.96 0.13 0.68 0.13 22.77 11.81 10.96 1.08 45 24 0.11 0.04 0.08 0.01 10.51 7.39 3.12 2.37 40 25 6.91 1.02 7.62 1.34 54.39 12.25 42.14 0.29 15 26 5.16 0.72 5.18 1.07 33.13 6.09 27.04 0.23 10 27 7.82 0.91 6.78 1.09 48.07 7.81 40.26 0.19 6 28 0.55 0.04 0.84 0.21 27.68 21.56 6.12 3.52 112 29 0.07 0.00 0.29 0.00 55.44 54.42 1.02 53.35 120 30 0.07 0.01 0.17 0.03 39.38 38.59 0.79 48.85 108 31 0.04 0.02 0.24 0.05 57.57 56.62 0.95 59.60 105 32 0.04 0.00 0.37 0.06 41.12 40.31 0.81 49.77 145 33 0.05 0.01 0.45 0.09 69.14 67.45 1.69 39.91 166 34 0.11 0.04 0.24 0.04 13.52 12.80 0.72 17.78 179 35 0.07 0.03 0.10 0.02 10.97 10.62 0.35 30.34 152 36 0.02 0.00 0.14 0.03 14.25 13.74 0.51 26.94 169 37 0.02 0.01 0.00 0.02 2.96 2.77 0.19 14.58 134 38 0.00 0.00 0.00 0.00 4.15 3.93 0.22 17.86 200 39 0.00 0.01 0.00 0.01 3.45 3.37 0.08 42.13 166 Note: The unit of D is meter, and the unit of elements is ppm. [0049] (4) Exponential models D=a(L/H){circumflex over ()}b (model 1) and D=a(L/H){circumflex over ()}b+c (model 2) are obtained by substituting the ratio (L/H) of the light rare earth content to the heavy rare earth content and the distance D into a linear model y=bx+a, and a logarithmic model D=a(ln(L/H)+4){circumflex over ()}(b+0.1) (model 3) is obtained by substituting the ratio (L/H) of the light rare earth content to the heavy rare earth content and the distance D into a logarithmic model y=bln(x)+a, as shown in FIG. 2.

[0050] A specific implementation mode further provides a method for determining a direction and a distance of a metallogenic pluton of a skarn deposit with a gamet. The method includes: [0051] (1) A sample is collected: [0052] a representative garnet sample is collected from the skarn. [0053] (2) Petrographic observation is performed on the sample and an experimental area is designed: [0054] the collected sample is ground into a thin section, and a single mineral crystal area of the garnet is determined and marked. [0055] (3) A parameter is computed: [0056] A trace element content of the marked area is obtained through LA-ICPMS in-situ microanalysis, and a ratio (L/H) of a light rare earth content to a heavy rare earth content is computed, as shown in FIG. 3.

TABLE-US-00003 TABLE 3 Computation Results No X(m) Y(m) La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Tm Yb Lu LREE HREE L/H 1 136.29 52.73 0.15 0.3 0.24 1.76 2.34 1.5 1.73 0.24 0.77 0.14 0.11 0.04 0.08 0.01 6.29 3.12 2.02 2 411.46 365.65 0.71 0.9 0.05 0 0.2 0.04 0.1 0 0.03 0.01 0.02 0.01 0 0.02 1.9 0.19 10.00 3 283.26 223.65 7.15 0 1.1 2.79 0.43 0.05 0.11 0.01 0.15 0.02 0.11 0.04 0.24 0.04 11.52 0.72 16.00 4 264.74 453.32 2.8 1.58 0.05 0.16 0 0.03 0.16 0 0.06 0 0 0 0 0 4.62 0.22 21.00 5 313.36 484.08 4.27 6.56 0.58 1.52 0.31 0.01 0.26 0.02 0.03 0.01 0.02 0 0.14 0.03 13.25 0.51 25.98 6 411.46 365.65 1.48 0.89 0.05 0 0.2 0.04 0.1 0 0.03 0.01 0.02 0.01 0 0.02 2.68 0.19 14.00 7 509.56 247.22 9.82 21.79 2.19 6.15 0.34 0.13 0.26 0.05 0 0.03 0.04 0 0.37 0.06 40.42 0.81 49.90 8 607.66 128.8 3.51 4.68 0.57 1.63 0.1 0.01 0.05 0.01 0.06 0.01 0.07 0.03 0.1 0.02 10.62 0.35 30.00 9 705.77 10.37 8.17 23.38 5.16 16.78 1.95 0.32 0.69 0.11 0.27 0.02 0.05 0.01 0.45 0.09 55.65 1.69 32.99 Note: The unit of X and Y is meter, and the unit of elements is ppm. [0057] (4) A model is built: [0058] the ratio (L/H) of the light rare earth content to the heavy rare earth content obtained is substituted into exponential models D=a(L/H){circumflex over ()}b and D=a(L/H){circumflex over ()}b+c and a logarithmic model D=a(In(L/H)+4){circumflex over ()}(b+0.1). [0059] (5) A parameter range is set: [0060] a parameter a?[?1000,1000] is set with a step size of 50, and a parameter b ? [?10,10] is set with a step size of 0.5 in the exponential model D=a(L/H){circumflex over ()}b; [0061] a parameter a?[?1000,1000] is set with a step size of 50, a parameter b ?[?10,10] is set with a step size of 0.5, and a parameter c?[?1000,1000] is set with a step size of 50 in the exponential model D=a(L/H){circumflex over ()}b+c; and [0062] a parameter a?[?1000,1000] is set with a step size of 50, and a parameter b ? [?10,10] is set with a step size of 0.5 in the logarithmic model D=a(ln(L/H)+4){circumflex over ()}(b+0.1). [0063] (6) Parameters of the model are optimized: [0064] the parameters of the three models are optimized through a grid search method, and optimized parameters a, b and c of the three models are determined respectively through repeated circulative iteration and by taking a minimum R as a limit condition; [0065] where R represents an optimized buffer radius:

[00002]$R=\frac{\underset{n}{\overset{i=1}{.Math.}}{D}^{}}{n}=\frac{\underset{n}{\overset{i=1}{.Math.}}.Math.\left(D_i-r_i\right).Math.}{n},$

and has a threshold?60 m; and [0066] n represents the samples number, i represents a sampling point i, D.sub.i represents a linear distance in m between an optimal location of the metallogenic pluton and the sampling point i, r.sub.i represents a linear distance in m between a location of the metallogenic pluton obtained from an optimal parameter model for the sampling point i and the sampling point i, and D represents an absolute value in m of a difference between D.sub.i and r.sub.i.

[0067] If the R is still greater than 60 m (a-c shown in FIG. 3), ranges of parameters a, b and c are needed to be redefined according to the parameters a, b and c returned after iteration and the step size is reduced until R returned is less than 60 m (d-f shown in FIG. 3). [0068] (7) The metallogenic pluton is located and delineated: [0069] a model with minimum R among the three models is taken as an optimal model, data of all sampling points are substituted into the optimal model, D of each sampling point is computed, a circle is drawn with each sampling point as a center and D as the radius, an intersection point with minimum R (38 m) of intersection points of all circles is determined as locational coordinates (X=?216 m, Y=?389 m) of the metallogenic pluton, that is, a location of a five-pointed star (e shown in FIG. 3), and delineation is performed with R (38 m) as a buffer area of the metallogenic pluton (e shown in FIG. 3).

[0070] It will be appreciated by those of ordinary skill in the art that examples herein are used for helping a reader to understand the implementation method of the present disclosure, and it should be understood that the protection scope of the present disclosure is not limited to such special statements and examples. Those of ordinary skill in the art can make other various specific modifications and combinations according to the technical teachings disclosed in the present disclosure without departing from the essence of the present disclosure.