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Crust data analysis method, crust data analysis program, and crust data analysis device

Foreign code F190009673
File No. B000022AU
Posted date Jan 22, 2019
Country Australia
Application number 2014307511
Gazette No. 2014307511
Date of filing Jun 12, 2014
Gazette Date Feb 25, 2016
International application number JP2014065556
International publication number WO2015022806
Date of international filing Jun 12, 2014
Date of international publication Feb 19, 2015
Priority data
  • P2013-168564 (Aug 14, 2013) JP
  • 2014JP65556 (Jun 12, 2014) WO
Title Crust data analysis method, crust data analysis program, and crust data analysis device
Abstract A crust data analysis device (1) is provided with: an acquisition unit (41) for acquiring a plurality of data items indicating the crustal abundance of a prescribed element or compound at a plurality of locations; a generation unit (42) for using differing first thresholds to delete, from the plurality of data items, data for which the crustal abundance is greater than or equal to the first threshold corresponding to the data item and generating a plurality of data items for which deletion has been completed; a determination unit (43) for determining whether the data composing the data items for which deletion has been completed conforms to a normal distribution having the average crustal abundance of the prescribed element or compound within an area larger than the area including the plurality of positions as the mean thereof; and a setting unit (44) for setting a geochemical anomaly threshold to the maximum crustal abundance value in the data item for which deletion has been completed having the smallest amount of data from among the plurality of data items for which deletion has been completed that have been determined to not conform to the normal distribution.
Outline of related art and contending technology BACKGROUND OF THE INVENTION
In data analysis of geochemical exploration, it is known that the amount of contained material in a plurality of samples gathered from a crust has a normal distribution in a common logarithm.FIG. 9 shows an example of a frequency distribution of a background value corresponding to a common content ratio of contained elements and an anomalous value indicating the presence of a mineral occurrence in each rock in the plurality of samples gathered from the crust.In FIG. 9, the horizontal axis represents the amount of contained material in a common logarithm and the vertical axis represents a number of samples corresponding to each of the amount of contained material.FIG. 9 shows a frequency distribution FD1 of the background value and a frequency distribution FD2 of the anomalous value.The frequency distribution FD1 of the background value and the frequency distribution FD2 of the anomalous value tend to have a normal distribution independently.
Conventionally, a threshold value of elements contained in the plurality of samples is set with respect to a frequency distribution of the elements contained in the plurality of samples in order to separate the plurality of samples gathered from the crust into a background population and an anomalous population.
For example, a technique is disclosed for reading the threshold value between the background population and the anomalous population according to a bending point of a straight line in the cumulative frequency distribution by focusing on the fact that the plurality of pieces of data belonging to a population that has a normal distribution in a common logarithm shows the straight line in the cumulative frequency distribution among data indicating the amount of contained material of each of the plurality of samples (for example, see Non-Patent Document 1).
FIG. 10 is a cumulative frequency distribution map of the analytical values of each element in each of the plurality of samples.In FIG. 10, the horizontal line represents the amount of content of each element and the vertical line represents a normal distribution probability.In FIG. 10, for example, it can be recognized that the straight line indicating the cumulative frequency of molybdenum (Mo) bends at about 2 ppm and at about 8 ppm.Hence, it can be recognized that the line segment of about 2 ppm or less is formed by the background population, the line segment from about 2 ppm to about 8 ppm is formed by the background population and the anomalous population, and the line segment of about 8 ppm or more is formed by the anomalous population.Accordingly, a threshold value between the population corresponding to the background value and the population corresponding to the anomalous value of Mo can be set between about 2 ppm and about 8 ppm.Further, as another technique for determining the threshold value, a technique that determines a threshold value with a multiple of a value obtained by adding the standard deviation to the average value of the common logarithm is disclosed (for example, see Non-Patent Document 2).
Scope of claims [claim1]
1. A crust data analysis method comprising: acquiring a plurality of pieces of data indicating crustal abundances of predetermined elements or compounds at a plurality of positions; generating a plurality of pieces of non-deleted data by deleting a portion of data from the plurality of pieces of data; deciding whether or not a plurality of pieces of data constituting the non-deleted data has a normal distribution with respect to each piece of the plurality of pieces of non-deleted data; and determining a threshold value of geochemical anomalies on the basis of a result of the decision.
[claim2]
2. The crust data analysis method according to Claim 1, wherein the generating the plurality of pieces of non-deleted data generates a plurality of pieces of non-deleted data by deleting data in which the crustal abundances of the plurality of pieces of data is equal to or greater than the first threshold value from the plurality of pieces of data by using each different first threshold value, the deciding decides whether or not a plurality of pieces of data constituting the non-deleted data has a normal distribution in which an average value is the average crustal abundance of the predetermined elements or compounds in an area that is wider than an area including the plurality of positions, and the determining the threshold value determines a value within a predetermined range from the largest crustal abundance value in the non-deleted data with the smallest number of pieces of data among the plurality of pieces of non-deleted data that was decided not to have a normal distribution to be the threshold value of geochemical anomalies.
[claim3]
3. The crust data analysis method according to Claim 2, wherein the generating the plurality of pieces of non-deleted data generates the plurality of pieces of non-deleted data by deleting data in which the crustal abundance of the plurality of pieces of data is equal to or greater than the first threshold value by using each different first threshold value and by deleting data that is equal to or less than a second threshold value by using the second threshold value that is lower than the first threshold value from the plurality of pieces of data.
[claim4]
4. The crust data analysis method according to Claim 3, wherein the second threshold value is a detection limitation of the crustal abundance, and the generating the plurality of pieces of non-deleted data generates the non-deleted data by deleting data that is equal to or greater than the first threshold value after deleting the data that is equal to or less than the second threshold value.
[claim5]
5. The crust data analysis method according to any one of Claims 2 to 4, wherein the generating the plurality of pieces of non-deleted data generates the plurality of pieces of non-deleted data by sequentially reducing the first threshold value, and the deciding makes the decision after a piece of the non-deleted data is generated.
[claim6]
6. The crust data analysis method according to any one of Claims 2 to 4, wherein the generating the plurality of pieces of non-deleted data determines the first threshold value on the basis of a binary search and generates the non-deleted data on the basis of the determined first threshold value.
[claim7]
7. A crust data analysis program that causes a computer to operate as: an acquiring section that acquires a plurality of pieces of data indicating crustal abundances of predetermined elements or compounds at a plurality of positions, a generating section that generates a plurality of pieces of non-deleted data by deleting a portion of data from the plurality of pieces of data, a deciding section that decides whether or not a plurality of pieces of data constituting the non-deleted data has a normal distribution with respect to each piece of the plurality of pieces of non-deleted data, and a determining section that determines a threshold value of geochemical anomalies on the basis of a result of the decision.
[claim8]
8. A crust data analysis device comprising: an acquiring section that acquires a plurality of pieces of data indicating crustal abundances of predetermined elements or compounds at a plurality of positions; a generating section that generates a plurality of pieces of non-deleted data by deleting a portion of data from the plurality of pieces of data; a deciding section that decides whether or not a plurality of pieces of data constituting the non-deleted data has a normal distribution with respect to each piece of the plurality of pieces of non-deleted data; and a determining section that determines a threshold value of geochemical anomalies on the basis of a result of the decision.
  • Applicant
  • Japan Oil, Gas and Metals National Corporation
  • Inventor
  • Morozumi, Haruhisa
IPC(International Patent Classification)

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