I have read about and heard about the theory that most of the heavy elements we have here on Earth came from colliding neutron stars rather than by way of supernovae.
I'm not sure how strong this theory is, but I wonder if a LIGO (and backup observational/ gamma ray) detection would help answer this question in any way.
I just found out the answer to my question from a live press release on You Tube that has been covered by blogs like this: http://news.nationalgeographic.com/2017/10/gravitational-waves-discovered-neutron-stars-pictures-science/
What LIGO does is tell you what is causing the gamma ray burst that can be studied different ways. The highly anticipated announcement I just watched explained that LIGO observed the neutron star merger (they're calling the event a kilonova). With the help of VIRGO, the area of the sky could be narrowed down better than previous LIGO detections. LIGO told us the masses of the bodies, the distance to the objects, how much mass was ejected and thus what the end product of the collision is expected to be.
We have observed many gamma ray bursts and this one was not particularly bright, but LIGO told astronomers to check this one out and so it was being observed within a few hours.
The electromagnetic spectrum of this event was collected and very broad lines were detected which are believed to be caused by heavy elements being ejected at near light speeds.
By our knowledge of how often these "kilonovae" should happen and the volume of elements heavier than iron thought now to have been emitted (16 Earth masses was the number mentioned in the press release), it can be said that a majority of many of the heavy elements we see around us may have come from these events.
It seems very likely that merging neutron stars are a major contributor to some of the (heavier) elements in the universe. These elements are made by rapid neutron capture onto pre-existing seed nuclei - known as the r-process. The process could work well in the hot ejecta created by the merger of two neutron stars.
Whether this mechanism dominates the creation of these elements is still uncertain. Firstly, there are other possible r-process sites - most obviously, supernovae, that may also be important. Secondly, in order to compare the production rates in neutron star mergers with the abundances of heavy elements in say the Solar System, we need to know what the rate of these neutron star mergers is, as a function of cosmic time, and we need to know how much of what chemical elements are produced in the merger.
What the new LIGO gravitational wave observations give us, is some very approximate idea of the rate at which these mergers are happening. But it is still order-of-magnitude stuff. The second important thing is that via the identification of an optical/infrared counterpart to one of these mergers one is able to study the chemical composition of the ejecta in some detail. These observations are broadly consistent with the idea that the ejecta contain a lot of material that is produced in the r-process, though don't really give much information on the abundances of individual chemical elements.
I would conclude that the one detection of GW170817 has moved us from an upper limit on the merger rate to an order-of-magnitude estimate, and the identification of the signatures of r-process elements in the ejecta tells us that mergers can produced heavy elements in some quantity. This is consistent with the notion that most of some specific heavy elements are produced in this way, but the detailed quantitative evidence for that is still some way off.
