Hi Richard, my philosophy has long been that the core correction factor is not worth worrying about for exactly the reason you mention. I am interested in an interval that is 20 times as magnetic as the surrounding intervals, not 1.7 times... Regards, Chris
Original Message From: Richard Smith via SEGMIN Sent: Saturday, 15 September 2018 19:46 To: [email protected] Reply To: [email protected] Cc: Richard Smith Subject: Re: [SEGMIN] Magnetic susceptibility meter Hi Kim, I notice you got my post. I did not, so sent it again. It seems that the new SEGMIN might not sent it to the sender sometimes. I asked the student if he had used the core radius correction and he said he had, but as you say, it is not clear it is was set routinely each time the meter was turned on. If the data downloaded from the meter had an additional value, the correction applied or an uncorrected value, then that would assist in the QC. There are aspects of these magnetic susceptibility meters which are problematic in addition to the core radius correction. Another is how they deal with negative susceptibilities for diamagnetic rocks like quartzite. Table 2 in the paper I attached in the last message shows that the instruments return values that are sometimes zero, sometime positive and sometimes negative. The crossplots produced in figure 2 are on a log scale, so these negative values are ignored. Concerning the plot you attached. My comment is that the values are generally within a factor of two of each other. My experience of most magnetic susceptibility values on heterogeneous rocks is that a factor of two is less than the variability of the rock itself, so the readings are essentially the same. The core correction factor is generally a factor of two or so, so perhaps it is not significant in the grand scheme of things! RegardsRichard Smith -----Original Message----- From: Kim Frankcombe via SEGMIN <[email protected]> To: segmin <[email protected]> Cc: Kim Frankcombe <[email protected]> Sent: Sat, Sep 15, 2018 12:04 am Subject: Re: [SEGMIN] Magnetic susceptibility meter Richard When I reviewed the abstract for this as a SEG presentation I asked whether the non KT series meter readings had been corrected for sample size. I didn't get an answer at the time so perhaps you could clarify. As an additional piece of info attached or attached and scrubbed is a plot comparing SM-30, Magrock and KT5 against sample values returned from Don Emerson. We accepted Don's value as the truth and adjusted each reading for sample size using the manufacturer's tables. One of the samples was 1/4 NQ core so the sample size correction was a fiddle. I can't recall which one and would have to start a virtual machine to open the windows format spreadsheet sorry. Also not sure which mouse ate the bottom of the K in the axis titles - put it down to my usual scapegoat - microsoft. I suspect that when all thee meters cluster away from the truth that we have use a poor estimate for sample size correction Cheers Kim On 15/09/18 09:31, Richard Smith via SEGMIN wrote: > Attached is a recent review of mag susc meters. A few years out of date. I > hear the GDD is cheaper now. > Note that for attachments on the new SEGMIN list there is a link at the > bottom of the message, or you can check the archive > RegardsRichard Smith > > -----Original Message----- > From: Aline T. Melo via SEGMIN <[email protected]> > To: segmin <[email protected]> > Cc: Aline T. Melo <[email protected]> > Sent: Fri, Sep 14, 2018 3:36 pm > Subject: [SEGMIN] Magnetic susceptibility meter > > Hello, > > Does anyone has experience with KT-20 > susceptibility/conductivity/ip-resistivity meter ( > http://www.terraplus.ca/products/pdf/KT-20.pdf)? > Any pros and cons? > > I am looking for recommendations to buy a susceptibility meter, and > appreciate any help. > > Thanks! > Aline > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <https://lists.geosoft.com/mailman/private/segmin/attachments/20180914/1faa022c/attachment.html> > ----------------------- > SEGMIN community mailing list service ([email protected]). > Change your personal options here: > https://lists.geosoft.com/mailman/options/segmin/[email protected] > Colleagues can join here: https://lists.geosoft.com/mailman/listinfo/segmin > Archives: https://lists.geosoft.com/mailman/private/segmin/ > NOTE that <Reply> will reply to all members of the list. > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: > <https://lists.geosoft.com/mailman/private/segmin/attachments/20180915/6a60f45b/attachment.html> > -------------- next part -------------- > A non-text attachment was scrubbed... > Name: Deng and Smith 2016 preview.pdf > Type: application/pdf > Size: 512893 bytes > Desc: not available > URL: > <https://lists.geosoft.com/mailman/private/segmin/attachments/20180915/6a60f45b/attachment.pdf> > ----------------------- > SEGMIN community mailing list service ([email protected]). > Change your personal options here: > https://lists.geosoft.com/mailman/options/segmin/[email protected] > Colleagues can join here: https://lists.geosoft.com/mailman/listinfo/segmin > Archives: https://lists.geosoft.com/mailman/private/segmin/ > NOTE that <Reply> will reply to all members of the list. -- Signature file Kim Frankcombe Senior Consulting Geophysicist /ExploreGeo/ PO Box 1191, Wangara, WA 6947 AUSTRALIA Unit 6,10 O’Connor Way, Wangara, WA 6065, Australia Phone+61 (0)8 62017719- if your call goes to voice mail, leave a message. 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