Jared's Blog

First Blog

I am just starting my second week, as well as second year, in the Cosmogenic Radiation Lab (in Mitchell's Sub-basement) with Kim Blisniuk. We are continuing to date samples from offset features along the San Andreas in attempts to determine local slip rates. At the moment, we are processing a large amount of samples from Mission Creek and the Pushawalla sites.

This past week, the lab was flooded with samples from Mission Creek. As part of the first step in processing the samples, I spent most of last week in the Rock Room. We crushed the cobbles into sands, which we then manually sieved. After sieving, we soaked the 250-500 micron fractions in Hydrochloric Acid to leach organics from the samples. We are currently cleaning the samples from their HCl leach to prepare them for leaches in Hydrofluoric Acid, which will isolate the quartz in each sample.

Eventually, after all of the Hydrofluoric leaches are complete, we will use columns to remove ions from the samples. However, at the moment that portion of the lab has been contaminated from a flood that soaked the entire sub-basement a couple of weeks ago.

In some senses I am continuing the work we began last summer at the Sanborn site in Saratoga, Calif. In the past year, the samples from Sanborn were processed, dated, and analyzed in a process that spanned 10 months. I am being told that the data from those samples indicates a faster than expected slip rate (increased danger) in the area.

In the next couple of weeks I am looking forward to following along in the processing of the new samples.

Second Blog

In the past several weeks, I have continued the processing of the last set of samples. Since last updating, the processes have been frantzed, undergone heavy liquid separation, and been prepared for PSA.

Samples are frantzed in order to remove the magnetic minerals and iron filing in the samples that can act as contaminants. Frantzing involves using a large electro-magnet to pull out the waste from the actual sample. Frantzing is necessary because iron contaminates the heavy liquids needed for feldspar separation.

After samples are frantzed, they may undergo heavy liquid separation. Using this technique, “heavy” liquids with specific gravities of 2 to 3 are used to separate certain minerals from the sample. Because certain minerals are lighter than the heavy liquid, they float to the top allowing for easy separation and collection, while the unwanted minerals simply sink to below the liquid. We used heavy liquids in order to isolate the Potassium Feldspar (K-Spar) from our samples. Similar to beryllium dating, isotopes of chlorine found in the K-spar can be used to provide a second point of data and date the rocks.

I have also been preparing samples for Partial Sample Aliquots (PSA’s). PSA’s place small amounts of each sample under a mass spectrometer, which then analyzes the amounts of each element in the sample. If too much of certain elements are in the sample, the sample must be repeatedly cleaned before it can continue in the process of Beryllium extraction. To prepare samples for PSA, they are dissolved in both Aqua Regia (a mixture of HCl & Nitric Acid) and concentrated HCl, then evaporated.

In the coming weeks, we will be doing column chemistry in order to isolate the beryllium from the samples and prepare the beryllium for mass spectrometry to learn the ultimate age of the rocks.

Third Blog

In the last couple of weeks, we received the results from PSA, which told us that majority our samples are ready for final quartz dissolution. The samples are then soaked in Hydrochloric Acid and Aqua Regia to dissolve, and are then evaporated to just a couple milliliters. This remaining sample is fed through columns filled with ionized resin that allows us to isolate Aluminum ions, Titanium ions, but most importantly, the Beryllium ions. Once we have collected the Beryllium fraction from the sample, it is once again evaporated and then dissolved one more time. In this final solution, we can precipitate out the Beryllium and then prepare it in targets for mass spectrometry. Looking forward, I will be evaporating the final set of samples in the next couple days.

Although it is hard to deny the repetitive and often tedious nature of lab work, one cannot be deterred, knowing that all of our work pays off by increasing the shared knowledge in the field and knowledge of our world. I am grateful for the opportunity to contribute in the lab and for the opportunity to help in research.

To read more about Jared's adventures in 2013, see https://sites.google.com/site/earthscienceshighschool/2013-general-program-intern-blogs/jared-s-blog